Internet-Draft The GNU Name System February 2022
Schanzenbach, et al. Expires 18 August 2022 [Page]
Workgroup:
Independent Stream
Internet-Draft:
draft-schanzen-gns-07
Published:
Intended Status:
Informational
Expires:
Authors:
M. Schanzenbach
GNUnet e.V.
C. Grothoff
Berner Fachhochschule
B. Fix
GNUnet e.V.

The GNU Name System

Abstract

This document contains the GNU Name System (GNS) technical specification. GNS is a decentralized and censorship-resistant name system that provides a privacy-enhancing alternative to the Domain Name System (DNS).

This document defines the normative wire format of resource records, resolution processes, cryptographic routines and security considerations for use by implementers. It is published here to inform readers about the function of GNS, guide future GNS implementations, and ensure interoperability among implementations including with the pre-existing GNUnet implementation.

This specification was developed outside the IETF and does not have IETF consensus. It is published here to guide implementation of GNS and to ensure interoperability among implementations.

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.

Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."

This Internet-Draft will expire on 18 August 2022.

Table of Contents

1. Introduction

The Domain Name System (DNS) [RFC1035] is a unique distributed database and a vital service for most Internet applications. While DNS is distributed, in practice it relies on centralized, trusted registrars to provide globally unique names. As the awareness of the central role DNS plays on the Internet rises, various institutions are using their power (including legal means) to engage in attacks on the DNS, thus threatening the global availability and integrity of information on the Internet.

DNS was not designed with security in mind. This makes it very vulnerable, especially to attackers that have the technical capabilities of an entire nation state at their disposal. While a wider discussion of this issue is out of scope for this document, analyses and investigations can be found in recent academic research works including [SecureNS].

This specification describes a censorship-resistant, privacy-preserving and decentralized name system: The GNU Name System (GNS) [GNS]. It is designed to provide a secure, privacy-enhancing alternative to DNS, especially when censorship or manipulation is encountered. In particular, it directly addresses concerns in DNS with respect to "Query Privacy", the "Single Hierarchy with a Centrally Controlled Root" and "Distribution and Management of Root Servers" as raised in [RFC8324]. GNS can bind names to any kind of cryptographically secured token, enabling it to double in some respects as even as an alternative to some of today's Public Key Infrastructures, in particular X.509 for the Web.

The design of GNS incorporates the capability to integrate and coexist with DNS. GNS is based on the principle of a petname system and builds on ideas from the Simple Distributed Security Infrastructure [SDSI], addressing a central issue with the decentralized mapping of secure identifiers to memorable names: namely the impossibility of providing a global, secure and memorable mapping without a trusted authority. GNS uses the transitivity in the SDSI design to replace the trusted root with secure delegation of authority thus making petnames useful to other users while operating under a very strong adversary model.

This is an important distinguishing factor from the Domain Name System where root zone governance is centralized at the Internet Corporation for Assigned Names and Numbers (ICANN). In DNS terminology, GNS roughly follows the idea of a hyperlocal root zone deployment, with the difference that it is not expected that all deployments use the same local root zone, and that users can easily delegate control of arbitrary domain names to arbitrary zones.

This document defines the normative wire format of resource records, resolution processes, cryptographic routines and security considerations for use by implementers.

This specification was developed outside the IETF and does not have IETF consensus. It is published here to guide implementation of GNS and to ensure interoperability among implementations.

1.1. Requirements Notation

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.

2. Terminology

Label
A GNS label is a label as defined in [RFC8499]. Within this document, labels are always assumed to be strings of UTF-8 characters [RFC8499] with a maximum length of 63 bytes for compatibility with applications enforcing DNS legacy limitations. Labels MUST be canonicalized using Normalization Form C (NFC) [Unicode-UAX15].
Apex Label
The apex label is represented using the character "@" (without quotes). The apex label is used to publish resource records in a zone that can be resolved without providing a specific label. It is the GNS method to provide what is the "zone apex" in DNS [RFC4033].
Name
A name in GNS is a domain name as defined in [RFC8499] as an ordered list of labels. The labels in a name are separated using the character "." (dot). Names, like labels, are encoded in UTF-8.
Top-Level Domain
The rightmost part of a GNS name is a GNS Top-Level Domain (TLD). A GNS TLD may consist of one or more labels. Unlike DNS Top-Level Domains (defined in [RFC8499]), GNS does not expect all users to use the same global root zone. Instead, with the exception of Zone Top-Level Domains (see below), GNS TLDs are typically part of the configuration of the local resolver (see Section 7.1), and may thus not be globally unique.
Zone
A GNS zone contains authoritative information (resource records). A zone is uniquely identified by its zone key. Unlike DNS zones, a GNS zone does not need to have a SOA record under the apex label.
Zone Type
The type of a GNS zone determines the cipher system and binary encoding format of the zone key, blinded zone keys, and signatures.
Zone Key
The zone key uniquely identifies a zone. The zone key is usually a public key of an asymmetric key pair.
Blinded Zone Key
A blinded zone key is derived from the zone key and a label. The zone key and the blinded zone key are unlinkable without knowledge of the label.
Zone Key Derivation Function
The zone key derivation function (ZKDF) blinds a key using a label. There are different functions for public and private keys, respectively.
Zone Owner
The owner of a GNS zone is the holder of the secret (typically a private key) that (together with a label and a value to sign) allows the creation of zone signatures that can be validated against the respective blinded zone key.
Zone Top-Level Domain
A GNS Zone Top-Level Domain (zTLD) is a sequence of GNS labels at the end of a GNS name which encodes a zone type and zone key of a zone. Due to the statistical uniqueness of zone keys, zTLDs are also globally unique. A zTLD label sequence can only be distinguished from ordinary TLD label sequences by attempting to decode the labels into a zone type and zone key.
Resource Record
A GNS resource record is the information associated with a label in a GNS zone. A GNS resource record contains information as defined by its resource record type.
Application
An application refers to a component which uses a GNS implementation to resolve names into records and processes its contents.

3. Overview

In GNS, any user may create and manage one or more cryptographically secured zones (Section 4). Zones are uniquely identified by a zone key. Zone contents are signed using blinded private keys and encrypted using derived secret keys. The zone type determines the respective set of cryptographic operations and the wire formats for encrypted data, public keys and signatures.

A zone can be populated with mappings from labels to resource records by its owner (Section 5). A label can be mapped to a delegation record which results in the corresponding subdomain being delegated to another zone. Circular delegations are explicitly allowed, including delegating a subdomain to its immediate parent zone. In order to support (legacy) applications as well as to facilitate the use of petnames, GNS defines auxiliary record types in addition to supporting traditional DNS records.

Zone contents are encrypted and signed before being published in a distributed key-value storage (Section 6). In this process, unique zone identification is hidden from the network through the use of key blinding. Key blinding allows the creation of signatures for zone contents using a blinded public/private key pair. This blinding is realized using a deterministic key derivation from the original zone key and corresponding private key using record label values as blinding factors. Specifically, the zone owner can derive blinded private keys for each record set published under a label, and a resolver can derive the corresponding blinded public keys. It is expected that GNS implementations use distributed or decentralized storages such as distributed hash tables (DHT) in order to facilitate availability within a network without the need for dedicated infrastructure. Specification of such a distributed or decentralized storage is out of scope of this document, but possible existing implementations include those based on [RFC7363], [Kademlia] or [R5N].

Names in GNS are domain names as defined in [RFC8499]. Starting from a configurable start zone, names are resolved by following zone delegations. For each label in a name, the recursive GNS resolver fetches the respective record from the storage layer (Section 7). Without knowledge of the label values and the zone keys, the different derived keys are unlinkable both to the original zone key and to each other. This prevents zone enumeration (except via impractical online brute force attacks) and requires knowledge of both the zone key and the label to confirm affiliation of a query or the corresponding encrypted record set with a specific zone. At the same time, the blinded zone key provides resolvers with the ability to verify the integrity of the published information without disclosing the originating zone.

In the remainder of this document, the "implementer" refers to the developer building a GNS implementation including, for example, zone management tools and name resolution components.

4. Zones

A zone in GNS is uniquely identified by its zone type and zone key. Each zone can be represented by a Zone Top-Level Domain (zTLD) string.

A implementation SHOULD enable the user to create and manage zones. If this functionality is not implemented, names can still be resolved if zone keys for the initial step in the name resolution are available (see Section 7).

Each zone type (ztype) is assigned a unique 32-bit number when it is registered in the GNUnet Assigned Numbers Authority [GANA]. The ztype determines which cryptosystem is used for the asymmetric and symmetric key operations of the zone. The ztype number always corresponds to a resource record type number identifying a delegation into a zone of this type. To ensure that there are no conflicts with DNS record types, ztypes are always assigned numeric values above 65535.

For any zone, let d be the private key and zk the public zone key. The specific wire format used depends on the ztype. The creation of zone keys for the default ztypes are specified in Section 5.1. New ztypes may be specified in the future, for example if the cryptographic mechanisms used in this document are broken. Any ztype MUST define the following set of cryptographic functions:

KeyGen() -> d, zk
is a function to generate a new private key d and the corresponding public zone key zk.
ZKDF-Private(d,label) -> d'
is a zone key derivation function which blinds a private key d using label, resulting in another private key which can be used to create cryptographic signatures. We note that GNS only requires a signature to be created directly with d to sign a revocation message for the zone key zk.
ZKDF-Public(zk,label) -> zk'
is a zone key derivation function which blinds a zone key zk using a label. zk and zk' must be unlinkable. Furthermore, blinding zk with different values for the label must result in different, unlinkable zk' values.
S-Encrypt(zk,label,expiration,message) -> ciphertext
is a symmetric encryption function which encrypts the record data based on key material derived from the zone key, a label, and an expiration timestamp. In order to leverage performance-enhancing caching features of certain underlying storages, in particular DHTs, a deterministic encryption scheme is recommended.
S-Decrypt(zk,label,expiration,ciphertext) -> message
is a symmetric decryption function which decrypts the encrypted record data based on key material derived from the zone key, a label, and an expiration timestamp.
Sign(d,message) -> signature, SignDerived(d,label,message) -> signature
is a function to sign a message (typically encrypted record data) using the (blinded) private key d (d'), yielding an unforgeable cryptographic signature. In order to leverage performance-enhancing caching features of certain underlying storages, in particular DHTs, a deterministic signature scheme is recommended.
Verify(zk,message,signature) -> boolean, VerifyDerived(zk,label,message,signature) -> boolean
is a function to verify the signature was created by the private key d (or derived key d') corresponding to the zone key zk (or derived zone key zk') where d,zk := Keygen(). If derivations were used, they must have used the same label. The function returns a boolean value of "TRUE" if the signature is valid, and otherwise "FALSE".

4.1. Zone Top-Level Domain

0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|       ZONE TYPE       |      ZONE KEY         /
+-----+-----+-----+-----+                       /
/                                               /
/                                               /
Figure 1

The decoded binary representation of the zTLD

The zTLD is the Zone Top-Level Domain. It is a string which encodes the zone type and zone key into a domain name. The zTLD is used as a globally unique reference to a specific namespace in the process of name resolution. To encode the zone key, a zone key label zkl is derived from a concatenation of the zone type and zone key (see Figure 1). The result is encoded using a variation of the Crockford Base32 encoding [CrockfordB32] called Base32GNS. The encoding and decoding symbols for Base32GNS including this modification are defined in Figure 23. The functions for encoding and decoding based on this table are called Base32GNS-Encode and Base32GNS-Decode, respectively.

For the string representation of a zTLD we define:

zkl := Base32GNS-Encode(ztype||zkey)
ztype||zkey := Base32GNS-Decode(zkl)

If zkl is less than 63 characters, it can directly be used as a zTLD. If zkl is longer than 63 characters, the zTLD is constructed by dividing zkl into smaller labels separated by the label separator ".". Here, the most significant bytes of the "ztype||zkey" concatenation must be contained in the rightmost label of the resulting string and the least significant bytes in the leftmost label of the resulting string. This allows the resolver to determine the ztype and zkl length from the rightmost label and to subsequently determine how many labels the zTLD should span. For example, assuming a zkl of 130 characters, the encoding would be:

zTLD := zkl[126..129].zkl[63..125].zkl[0..62]

4.2. Zone Revocation

Whenever a resolver encounters a new GNS zone, it MUST check against the local revocation list whether the respective zone key has been revoked. If the zone key was revoked, the resolution MUST fail with an empty result set.

In order to revoke a zone key, a signed revocation message MUST be published. This message MUST be signed using the private key. The revocation message is broadcast to the network. The specification of the broadcast mechanism is out of scope for this document. A possible broadcast mechanism for efficient flooding in a distributed network is implemented in [GNUnet]. Alternatively, revocation messages could also be distributed via a distributed ledger or a trusted central server. To prevent flooding attacks, the revocation message MUST contain a proof of work (PoW). The revocation message including the PoW MAY be calculated ahead of time to support timely revocation.

For all occurrences below, "Argon2id" is the Password-based Key Derivation Function as defined in [RFC9106]. For the PoW calculations the algorithm is instantiated with the following parameters:

S
The salt. Fixed 16-byte string: "GnsRevocationPow".
t
Number of iterations: 3
m
Memory size in KiB: 1024
T
Output length of hash in bytes: 64
p
Parallelization parameter: 1
v
Algorithm version: 0x13
y
Algorithm type (Argon2id): 2
X
Unused
K
Unused

Figure 2 illustrates the format of the data "P" on which the PoW is calculated.

0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|                      POW                      |
+-----------------------------------------------+
|                   TIMESTAMP                   |
+-----------------------------------------------+
|       ZONE TYPE       |    ZONE KEY           |
+-----+-----+-----+-----+                       |
/                                               /
/                                               /
+-----+-----+-----+-----+-----+-----+-----+-----+
Figure 2

The Format of the PoW Data.

POW
A 64-bit value that is a solution to the PoW. In network byte order.
TIMESTAMP
denotes the absolute 64-bit date when the revocation was computed. In microseconds since midnight (0 hour), January 1, 1970 UTC in network byte order.
ZONE TYPE
is the 32-bit zone type.
ZONE KEY
is the 256-bit public key zk of the zone which is being revoked. The wire format of this value is defined by the ZONE TYPE.

Traditionally, PoW schemes require to find a POW value such that at least D leading zeroes are found in the hash result. D is then referred to as the difficulty of the PoW. In order to reduce the variance in time it takes to calculate the PoW, we require that a number Z different PoWs must be found that on average have D leading zeroes.

The resulting proofs may then published and disseminated. The concrete dissemination and publication methods are out of scope of this document. Given an average difficulty of D, the proofs have an expiration time of EPOCH. With each additional bit difficulty, the lifetime of the proof is prolonged for another EPOCH. Consequently, by calculating a more difficult PoW, the lifetime of the proof can be increased on demand by the zone owner.

The parameters are defined as follows:

Z
The number of PoWs required is fixed at 32.
D
The minimum average difficulty is fixed at 22.
EPOCH
A single epoch is fixed at 365 days.

The revocation message wire format is illustrated in Figure 3.

0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|                   TIMESTAMP                   |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                      TTL                      |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                     POW_0                     |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                       ...                     |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                     POW_Z-1                   |
+-----------------------------------------------+
|       ZONE TYPE       |    ZONE KEY           |
+-----+-----+-----+-----+                       |
/                                               /
/                                               /
+-----+-----+-----+-----+-----+-----+-----+-----+
|                   SIGNATURE                   |
/                                               /
/                                               /
|                                               |
+-----+-----+-----+-----+-----+-----+-----+-----+
Figure 3

The Revocation Message Wire Format.

TIMESTAMP
denotes the absolute 64-bit date when the revocation was computed. In microseconds since midnight (0 hour), January 1, 1970 UTC in network byte order. This is the same value as the time stamp used in the individual PoW calculations.
TTL
denotes the relative 64-bit time to live of the record in microseconds also in network byte order. This field is informational for a verifier. A verifier MAY discard a revocation without checking the POW values or the signature if the TTL (in combination with TIMESTAMP) indicates that the revocation has already expired. However, the actual TTL of the revocation must be determined by examining the leading zeroes in the proof of work calculation.
POW_i
The values calculated as part of the PoW, in network byte order. Each POW_i MUST be unique in the set of POW values. To facilitate fast verification of uniqueness, the POW values must be given in strictly monotonically increasing order in the message.
ZONE TYPE
The 32-bit zone type corresponding to the zone key.
ZONE KEY
is the public key zk of the zone which is being revoked and the key to be used to verify SIGNATURE.
SIGNATURE
A signature over a time stamp and the zone zk of the zone which is revoked and corresponds to the key used in the PoW. The signature is created using the Sign() function of the cryptosystem of the zone and the private key (see Section 4).

The signature over the public key covers a 32-bit header prefixed to the time stamp and public key fields. The header includes the key length and signature purpose. The wire format is illustrated in Figure 4.

0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|         SIZE          |       PURPOSE (0x03)  |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                   TIMESTAMP                   |
+-----+-----+-----+-----+-----+-----+-----+-----+
|       ZONE TYPE       |     ZONE KEY          |
+-----+-----+-----+-----+                       |
/                                               /
/                                               /
+-----+-----+-----+-----+-----+-----+-----+-----+
Figure 4

The Wire Format of the Revocation Data for Signing.

SIZE
A 32-bit value containing the length of the signed data in bytes in network byte order.
PURPOSE
A 32-bit signature purpose flag. The value of this field MUST be 3. The value is encoded in network byte order. It defines the context in which the signature is created so that it cannot be reused in other parts of the protocol including possible future extensions. The value of this field corresponds to an entry in the GANA "GNUnet Signature Purpose" registry Section 10.
TIMESTAMP
Field as defined in the revocation message above.
ZONE TYPE
Field as defined in the revocation message above.
ZONE KEY
Field as defined in the revocation message above.

In order to verify a revocation the following steps MUST be taken:

  1. The signature MUST be verified against the zone key.
  2. The set of POW values MUST NOT contain duplicates which MUST be checked by verifying that the values are strictly monotonically increasing.
  3. The average number of leading zeroes D' resulting from the provided POW values MUST be greater than and not equal to D. Implementers MUST NOT use an integer data type to calculate or represent D'.
  4. The validation period (TTL) of the revocation is calculated as (D'-D) * EPOCH * 1.1. The EPOCH is extended by 10% in order to deal with unsynchronized clocks. The TTL added on top of the TIMESTAMP yields the expiration date. Should the verifier calculate the TTL and find that it differs from the field value, the verifier MUST continue and use the calculated value when forwarding the revocation.
  5. The current time SHOULD be between TIMESTAMP and TIMESTAMP+TTL. Implementations MAY process the revocation without validating this.

5. Resource Records

A GNS implementer SHOULD provide a mechanism to create and manage resource records for local zones. A new local zone is established by selecting a zone type and creating a zone key pair. As records may be added to each zone by its owner, a (local) persistence mechanism such as a database for resource records and zones SHOULD be provided. This local zone database is used by the name resolution logic and serves as a basis for publishing zones into the GNS storage (see Section 6).

A GNS resource record holds the data of a specific record in a zone. The resource record format is defined in Figure 5.

0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|                   EXPIRATION                  |
+-----+-----+-----+-----+-----+-----+-----+-----+
|    SIZE   |   FLAGS   |          TYPE         |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                      DATA                     /
/                                               /
/                                               /
Figure 5

The Resource Record Wire Format.

EXPIRATION
denotes the absolute 64-bit expiration date of the record. In microseconds since midnight (0 hour), January 1, 1970 UTC in network byte order.
SIZE
denotes the 16-bit size of the DATA field in bytes and in network byte order.
FLAGS
is a 16-bit resource record flags field (see below).
TYPE
is the 32-bit resource record type. This type can be one of the GNS resource records as defined in Section 5 or a DNS record type as defined in [RFC1035] or any of the complementary standardized DNS resource record types. This value must be stored in network byte order. Note that values below 2^16 are reserved for allocation via IANA [RFC6895], while values above 2^16 are allocated by the GNUnet Assigned Numbers Authority [GANA].
DATA
the variable-length resource record data payload. The content is defined by the respective type of the resource record.

Flags indicate metadata surrounding the resource record. A flag value of 0 indicates that all flags are unset. Applications creating resource records MUST set all bits which are not defined as a flag to 0. Additional flags may be defined in future protocol versions. If an application or implementation encounters a flag which it does not recognize, it MUST be ignored. Figure 6 illustrates the flag distribution in the 16-bit flag field of a resource record:

 0        1        2        3        4        5...
+--------+--------+--------+--------+--------+----
|CRITICAL|SHADOW  |SUPPL   |RESERVED
+--------+--------+--------+--------+--------+----
Figure 6

The Resource Record Flag Wire Format.

CRITICAL
If this flag is set, it indicates that processing is critical. Implementations that do not support the record type or are otherwise unable to process the record must abort resolution upon encountering the record in the resolution process.
SHADOW
If this flag is set, this record should be ignored by resolvers unless all (other) records of the same record type have expired. Used to allow zone publishers to facilitate good performance when records change by allowing them to put future values of records into the storage. This way, future values can propagate and may be cached before the transition becomes active.
SUPPL
This is a supplemental record. It is provided in addition to the other records. This flag indicates that this record is not explicitly managed alongside the other records under the respective name but may be useful for the application. This flag should only be encountered by a resolver for records obtained from the storage.

5.1. Zone Delegation Records

This section defines the initial set of zone delegation record types. Any implementation SHOULD support all zone types defined here and MAY support any number of additional delegation records defined in the GNU Name System Record Types registry (see Section 10). Zone delegation records MUST have the CRTITICAL flag set. Not supporting some zone types MAY result in resolution failures. This MAY BE a valid choice if some zone delegation record types have been determined to be cryptographically insecure. Zone delegation records MUST NOT be stored and published under the apex label. A zone delegation record type value is the same as the respective ztype value. The ztype defines the cryptographic primitives for the zone that is being delegated to. A zone delegation resource record payload contains the public key of the zone to delegate to. A zone delegation record MUST be the only record under a label. No other records are allowed.

5.1.1. PKEY

In GNS, a delegation of a label to a zone of type "PKEY" is represented through a PKEY record. The PKEY DATA entry wire format can be found in Figure 7.

0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|                   PUBLIC KEY                  |
|                                               |
|                                               |
|                                               |
+-----+-----+-----+-----+-----+-----+-----+-----+
Figure 7

The PKEY Wire Format.

PUBLIC KEY
A 256-bit Ed25519 public key.

For PKEY zones the zone key material is derived using the curve parameters of the twisted Edwards representation of Curve25519 [RFC7748] (a.k.a. Ed25519) with the ECDSA scheme [RFC6979]. Consequently, we use the following naming convention for our cryptographic primitives for PKEY zones:

d
is a 256-bit Ed25519 private key (private scalar).
zk
is the Ed25519 public zone key corresponding to d.
p
is the prime of edwards25519 as defined in [RFC7748], i.e. 2^255 - 19.
G
is the group generator (X(P),Y(P)) of edwards25519 as defined in [RFC7748].
L
is the order of the prime-order subgroup of edwards25519 in [RFC7748].
KeyGen()
The generation of the private scalar d and the curve point zk := d*G (where G is the group generator of the elliptic curve) as defined in Section 2.2. of [RFC6979] represents the KeyGen() function.

The zone type and zone key of a PKEY are 4 + 32 bytes in length. This means that a zTLD will always fit into a single label and does not need any further conversion.

Given a label, the output d' of the ZKDF-Private(d,label) function for zone key blinding is calculated as follows for PKEY zones:

ZKDF-Private(d,label):
  zk := d * G
  PRK_h := HKDF-Extract ("key-derivation", zk)
  h := HKDF-Expand (PRK_h, label || "gns", 512 / 8)
  d' := (h * d) mod L
  return d'

Equally, given a label, the output zk' of the ZKDF-Public(zk,label) function is calculated as follows for PKEY zones:

ZKDF-Public(zk,label)
  PRK_h := HKDF-Extract ("key-derivation", zk)
  h := HKDF-Expand (PRK_h, label || "gns", 512 / 8)
  zk' := (h mod L) * zk
  return zk'

The PKEY cryptosystem uses a hash-based key derivation function (HKDF) as defined in [RFC5869], using SHA-512 [RFC6234] for the extraction phase and SHA-256 [RFC6234] for the expansion phase. PRK_h is key material retrieved using an HKDF using the string "key-derivation" as salt and the zone key as initial keying material. h is the 512-bit HKDF expansion result and must be interpreted in network byte order. The expansion information input is a concatenation of the label and the string "gns". The label is a UTF-8 string under which the resource records are published. The multiplication of zk with h is a point multiplication, while the multiplication of d with h is a scalar multiplication.

The Sign() and Verify() functions for PKEY zones are implemented using 512-bit ECDSA deterministic signatures as specified in [RFC6979]. The same functions can be used for derived keys:

SignDerived(d,label,message):
  d' := ZKDF-Private(d,label)
  return Sign(d',message)

A signature (R,S) is valid if the following holds:

VerifyDerived(zk,label,message,signature):
  zk' := ZKDF-Public(zk,label)
  return Verify(zk',message,signature)

The S-Encrypt() and S-Decrypt() functions use AES in counter mode as defined in [MODES] (CTR-AES-256):

S-Encrypt(zk,label,expiration,plaintext):
  PRK_k := HKDF-Extract ("gns-aes-ctx-key", zk)
  PRK_n := HKDF-Extract ("gns-aes-ctx-iv", zk)
  K := HKDF-Expand (PRK_k, label, 256 / 8)
  NONCE := HKDF-Expand (PRK_n, label, 32 / 8)
  IV := NONCE || expiration || 0x0000000000000001
  return CTR-AES256(K, IV, plaintext)
Figure 8

The PKEY S-Encrypt Procedure.

S-Decrypt(zk,label,expiration,ciphertext):
  PRK_k := HKDF-Extract ("gns-aes-ctx-key", zk)
  PRK_n := HKDF-Extract ("gns-aes-ctx-iv", zk)
  K := HKDF-Expand (PRK_k, label, 256 / 8)
  NONCE := HKDF-Expand (PRK_n, label, 32 / 8)
  IV := NONCE || expiration || 0x0000000000000001
  return CTR-AES256(K, IV, ciphertext)
Figure 9

The PKEY S-Decrypt Procedure.

The key K and counter IV are derived from the record label and the zone key zk using a hash-based key derivation function (HDKF) as defined in [RFC5869]. SHA-512 [RFC6234] is used for the extraction phase and SHA-256 [RFC6234] for the expansion phase. The output keying material is 32 bytes (256 bits) for the symmetric key and 4 bytes (32 bits) for the nonce. The symmetric key K is a 256-bit AES [RFC3826] key.

The nonce is combined with a 64-bit initialization vector and a 32-bit block counter as defined in [RFC3686]. The block counter begins with the value of 1, and it is incremented to generate subsequent portions of the key stream. The block counter is a 32-bit integer value in network byte order. The initialization vector is the expiration time of the resource record block in network byte order. The resulting counter (IV) wire format can be found in Figure 10.

0     8     16    24    32
+-----+-----+-----+-----+
|         NONCE         |
+-----+-----+-----+-----+
|       EXPIRATION      |
|                       |
+-----+-----+-----+-----+
|      BLOCK COUNTER    |
+-----+-----+-----+-----+
Figure 10

The Block Counter Wire Format.

5.1.2. EDKEY

In GNS, a delegation of a label to a zone of type "EDKEY" is represented through a EDKEY record. The EDKEY DATA entry wire format is illustrated in Figure 11.

0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|                   PUBLIC KEY                  |
|                                               |
|                                               |
|                                               |
+-----+-----+-----+-----+-----+-----+-----+-----+
Figure 11

The EDKEY DATA Wire Format.

PUBLIC KEY
A 256-bit EdDSA zone key.

For EDKEY zones the zone key material is derived using the curve parameters of the twisted edwards representation of Curve25519 [RFC7748] (a.k.a. Ed25519) with the Ed25519 scheme [ed25519] as specified in [RFC8032]. Consequently, we use the following naming convention for our cryptographic primitives for EDKEY zones:

d
is a 256-bit EdDSA private key.
a
is is an integer derived from d using the SHA-512 hash function as defined in [RFC8032].
zk
is the EdDSA public key corresponding to d. It is defined as the curve point a*G where G is the group generator of the elliptic curve as defined in [RFC8032].
p
is the prime of edwards25519 as defined in [RFC8032], i.e. 2^255 - 19.
G
is the group generator (X(P),Y(P)) of edwards25519 as defined in [RFC8032].
L
is the order of the prime-order subgroup of edwards25519 in [RFC8032].
KeyGen()
The generation of the private key d and the associated public key zk := a*G where G is the group generator of the elliptic curve and a is an integer derived from d using the SHA-512 hash function as defined in Section 5.1.5 of [RFC8032] represents the KeyGen() function.

The zone type and zone key of an EDKEY are 4 + 32 bytes in length. This means that a zTLD will always fit into a single label and does not need any further conversion.

The "EDKEY" ZKDF instantiation is based on [Tor224]. The calculation of a is defined in Section 5.1.5 of [RFC8032]. Given a label, the output of the ZKDF-Private function for zone key blinding is calculated as follows for EDKEY zones:

ZKDF-Private(d,label):
  /* EdDSA clamping */
  a := SHA-512 (d)
  a[0] &= 248
  a[31] &= 127
  a[31] |= 64
  /* Calculate zk from d */
  zk := a * G

  /* Calculate the blinding factor */
  PRK_h := HKDF-Extract ("key-derivation", zk)
  h := HKDF-Expand (PRK_h, label || "gns", 512 / 8)
  /* Ensure that h == h mod L */
  h[31] &= 7

  a1 := a >> 3
  a2 := (h * a1) mod L
  d' := a2 << 3
  return d'

Equally, given a label, the output of the ZKDF-Public function is calculated as follows for PKEY zones:

ZKDF-Public(zk,label):
  /* Calculate the blinding factor */
  PRK_h := HKDF-Extract ("key-derivation", zk)
  h := HKDF-Expand (PRK_h, label || "gns", 512 / 8)
  /* Ensure that h == h mod L */
  h[31] &= 7

  zk' := h * zk
  return zk'

We note that implementers SHOULD employ a constant time scalar multiplication for the constructions above to protect against timing attacks. Otherwise, timing attacks may leak private key material if an attacker can predict when a system starts the publication process.

The EDKEY cryptosystem uses a hash-based key derivation function (HKDF) as defined in [RFC5869], using SHA-512 [RFC6234] for the extraction phase and HMAC-SHA256 [RFC6234] for the expansion phase. PRK_h is key material retrieved using an HKDF using the string "key-derivation" as salt and the zone key as initial keying material. The blinding factor h is the 512-bit HKDF expansion result. The expansion information input is a concatenation of the label and the string "gns". The result of the HKDF must be clamped and interpreted in network byte order. a is the 256-bit integer corresponding to the 256-bit private key d. The label is a UTF-8 string under which the resource records are published. The multiplication of zk with h is a point multiplication, while the division and multiplication of a and a1 with the co-factor are integer operations.

The Sign(d,message) and Verify(zk,message,signature) procedures MUST be implemented as defined in [RFC8032].

Signatures for EDKEY zones using the derived private scalar d' are not compliant with [RFC8032]. As the corresponding private key to the derived private scalar d' is not known, it is not possible to deterministically derive the signature part R according to [RFC8032]. Instead, signatures MUST be generated as follows for any given message and private zone key: A nonce is calculated from the highest 32 bytes of the expansion of the private key d and the blinding factor h. The nonce is then hashed with the message to r. This way, we include the full derivation path in the calculation of the R value of the signature, ensuring that it is never reused for two different derivation paths or messages.

SignDerived(d,label,message):
  /* EdDSA clamping */
  a := SHA-512 (d)
  a[0] &= 248
  a[31] &= 127
  a[31] |= 64
  /* Calculate zk from d */
  zk := a * G

  /* Calculate blinding factor */
  PRK_h := HKDF-Extract ("key-derivation", zk)
  h := HKDF-Expand (PRK_h, label || "gns", 512 / 8)

  d' := ZKDF-Private(d,label)
  dh := SHA-512 (d)
  nonce := SHA-256 (dh[32..63] || h)
  r := SHA-512 (nonce || message)
  R := r * G
  S := r + SHA-512(R || zk' || message) * d' mod L
  return (R,S)

A signature (R,S) is valid if the following holds:

VerifyDerived(zk,label,message,signature):
  zk' := ZKDF-Public(zk,label)
  (R,S) := signature
  return S * G == R + SHA-512(R, zk', message) * zk'

The S-Encrypt() and S-Decrypt() functions use XSalsa20 as defined in [XSalsa20] (XSalsa20-Poly1305):

S-Encrypt(zk,label,expiration,message):
  PRK_k := HKDF-Extract ("gns-xsalsa-ctx-key", zk)
  PRK_n := HKDF-Extract ("gns-xsalsa-ctx-iv", zk)
  K := HKDF-Expand (PRK_k, label, 256 / 8)
  NONCE := HKDF-Expand (PRK_n, label, 128 / 8)
  IV := NONCE || expiration
  return XSalsa20-Poly1305(K, IV, message)

S-Decrypt(zk,label,expiration,ciphertext):
  PRK_k := HKDF-Extract ("gns-xsalsa-ctx-key", zk)
  PRK_n := HKDF-Extract ("gns-xsalsa-ctx-iv", zk)
  K := HKDF-Expand (PRK_k, label, 256 / 8)
  NONCE := HKDF-Expand (PRK_n, label, 128 / 8)
  IV := NONCE || expiration
  return XSalsa20-Poly1305(K, IV, ciphertext)

The result of the XSalsa20-Poly1305 encryption function is the encrypted ciphertext followed by the 128-bit authentication tag. Accordingly, the length of encrypted data equals the length of the data plus the 16 bytes of the authentication tag.

The key K and counter IV are derived from the record label and the zone key zk using a hash-based key derivation function (HKDF) as defined in [RFC5869]. SHA-512 [RFC6234] is used for the extraction phase and SHA-256 [RFC6234] for the expansion phase. The output keying material is 32 bytes (256 bits) for the symmetric key and 16 bytes (128 bits) for the NONCE. The symmetric key K is a 256-bit XSalsa20 [XSalsa20] key. No additional authenticated data (AAD) is used.

The nonce is combined with an 8 byte initialization vector. The initialization vector is the expiration time of the resource record block in network byte order. The resulting counter (IV) wire format is illustrated in Figure 12.

0     8     16    24    32
+-----+-----+-----+-----+
|         NONCE         |
|                       |
|                       |
|                       |
+-----+-----+-----+-----+
|       EXPIRATION      |
|                       |
+-----+-----+-----+-----+
Figure 12

The Counter Block Initialization Vector

5.2. Redirection Records

Redirect records may be used to redirect resolution. Any implementation SHOULD support all redirection record types defined here and MAY support any number of additional redirection records defined in the GNU Name System Record Types registry (see Section Section 10). Redirection records MUST have the CRTITICAL flag set. Not supporting some record types MAY result in resolution failures. This MAY BE a valid choice if some redirection record types have been determined to be insecure, or if an application has reasons to not support redirection to DNS for reasons such as complexity or security. Redirection records MUST NOT be stored and published under the apex label.

5.2.1. REDIRECT

A REDIRECT record is the GNS equivalent of a CNAME record in DNS. A REDIRECT record MUST be the only record under a label. No other records are allowed. Details on processing of this record is defined in Section 7.3.1. A REDIRECT DATA entry is illustrated in Figure 13.

0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|                   REDIRECT NAME               |
/                                               /
/                                               /
|                                               |
+-----+-----+-----+-----+-----+-----+-----+-----+
Figure 13

The REDIRECT DATA Wire Format

REDIRECT NAME
The name to continue with. The value of a redirect record may be a regular name, or a relative name. Relative GNS names are indicated using the suffix ".+". The string is UTF-8 encoded and 0-terminated.

5.2.2. GNS2DNS

It is possible to delegate a label back into DNS through a GNS2DNS record. The resource record contains a DNS name for the resolver to continue with in DNS followed by a DNS server. Both names are in the format defined in [RFC1034] for DNS names. There MAY be multiple GNS2DNS records under a label. There MAY also be DNSSEC DS records or any other records used to secure the connection with the DNS servers under the same label. No other record types are allowed in the same record set. A GNS2DNS DATA entry is illustrated in Figure 14.

0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|                    DNS NAME                   |
/                                               /
/                                               /
|                                               |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                 DNS SERVER NAME               |
/                                               /
/                                               /
|                                               |
+-----------------------------------------------+
Figure 14

The GNS2DNS DATA Wire Format

DNS NAME
The name to continue with in DNS. The value is UTF-8 encoded and 0-terminated.
DNS SERVER NAME
The DNS server to use. May be an IPv4 address in dotted-decimal form or an IPv6 address in colon-hexadecimal form or a DNS name. It may also be a relative GNS name ending with a "+" as the rightmost label. The implementation MUST check the string syntactically for an IP address in the respective notation before checking for a relative GNS name. If all three checks fail, the name MUST be treated as a DNS name. The value is UTF-8 encoded and 0-terminated.

NOTE: If an application uses DNS names obtained from GNS2DNS records in a DNS request they must first be converted to an IDNA punycode representation [RFC5891].

5.3. Auxiliary Records

This section defines the initial set of auxiliary GNS record types. Any implementation SHOULD be able to process the specified record types according to Section 7.3.

5.3.1. LEHO

Applications can use the GNS to lookup IPv4 or IPv6 addresses of internet services. However, sometimes connecting to such services does not only require the knowledge of an address and port, but also requires the canonical DNS name of the service to be transmitted over the transport protocol. In GNS, legacy host name records provide applications the DNS name that is required to establish a connection to such a service. The most common use case is HTTP virtual hosting, where a DNS name must be supplied in the HTTP "Host"-header. Using a GNS name for the "Host"-header may not work as it may not be globally unique. Furthermore, even if uniqueness is not an issue, the legacy service might not even be aware of GNS. A LEHO resource record is expected to be found together in a single resource record with an IPv4 or IPv6 address. A LEHO DATA entry is illustrated in Figure 15.

0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|                 LEGACY HOSTNAME               |
/                                               /
/                                               /
|                                               |
+-----+-----+-----+-----+-----+-----+-----+-----+
Figure 15

The LEHO DATA Wire Format.

LEGACY HOSTNAME
A UTF-8 string (which is not 0-terminated) representing the legacy hostname.

NOTE: If an application uses a LEHO value in an HTTP request header (e.g. "Host:" header) it must be converted to an IDNA punycode representation [RFC5891].

5.3.2. NICK

Nickname records can be used by zone administrators to publish an the label that a zone prefers to have used when it is referred to. This is a suggestion to other zones what label to use when creating a delegation record (Section 5.1) containing this zone key. This record SHOULD only be stored under the apex label "@" but MAY be returned with record sets under any label as a supplemental record. Section 7.3.5 details how a resolver must process supplemental and non-supplemental NICK records. A NICK DATA entry is illustrated in Figure 16.

0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|                  NICKNAME                     |
/                                               /
/                                               /
|                                               |
+-----+-----+-----+-----+-----+-----+-----+-----+
Figure 16

The NICK DATA Wire Format.

NICKNAME
A UTF-8 string (which is not 0-terminated) representing the preferred label of the zone. This string MUST NOT include a "." character.

5.3.3. BOX

In GNS, with the notable exception of zTLDs, every "." in a name delegates to another zone. Furthermore, GNS lookups are expected to return all of the required useful information in one record set. This avoids unnecessary additional lookups and cryptographically ties together information that belongs together, making it impossible for an adversarial storage to provide partial answers that might omit information critical for security.

However, this general strategy is incompatible with the special labels used by DNS for SRV and TLSA records. Thus, GNS defines the BOX record format to box up SRV and TLSA records and include them in the record set of the label they are associated with. For example, a TLSA record for "_https._tcp.example.org" will be stored in the record set of "example.org" as a BOX record with service (SVC) 443 (https) and protocol (PROTO) 6 (tcp) and record TYPE "TLSA". For reference, see also [RFC2782]. A BOX DATA entry is illustrated in Figure 17.

0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|   PROTO   |    SVC    |       TYPE            |
+-----------+-----------------------------------+
|                 RECORD DATA                   |
/                                               /
/                                               /
|                                               |
+-----+-----+-----+-----+-----+-----+-----+-----+
Figure 17

The BOX DATA Wire Format.

PROTO
the 16-bit protocol number, e.g. 6 for tcp. Note that values below 2^8 are reserved for allocation via IANA [RFC5237], while values above 2^8 are allocated by the GNUnet Assigned Numbers Authority [GANA]. In network byte order.
SVC
the 16-bit service value of the boxed record. In case of TCP and UDP it is the port number. In network byte order.
TYPE
is the 32-bit record type of the boxed record. In network byte order.
RECORD DATA
is a variable length field containing the "DATA" format of TYPE as defined for the respective TYPE in DNS.

6. Record Storage

Any API which allows storing a value under a 512-bit key and retrieving one or more values from the key can be used by an implementation for record storage. To be useful, the API MUST permit storing at least 176 byte values to be able to support the defined zone delegation record encodings, and SHOULD allow at least 1024 byte values. We assume that an implementation realizes two procedures on top of a storage:

PUT(key,value)
GET(key) -> value

There is no explicit delete function as the deletion of a non-expired record would require a revocation of the record. In GNS, zones can only be revoked as a whole. Records automatically expire and it is under the discretion of the storage as to when to delete the record. The GNS implementation MUST NOT publish expired resource records. Any GNS resolver MUST discard expired records returned from the storage.

Resource records are grouped by their respective labels, encrypted and published together in a single resource records block (RRBLOCK) in the storage under a key q: PUT(q, RRBLOCK). The key q is derived from the zone key and the respective label of the contained records. The required knowledge of both zone key and label in combination with the similarly derived symmetric secret keys and blinded zone keys ensure query privacy (see [RFC8324], Section 3.5). The storage key derivation and records block creation is specified in the following sections. The implementation MUST use the PUT storage procedure in order to update the zone contents accordingly.

6.1. The Storage Key

Given a label, the storage key q is derived as follows:

q := SHA-512 (ZKDF-Public(zk, label))
label
is a UTF-8 string under which the resource records are published.
zk
is the zone key.
q
Is the 512-bit storage key under which the resource records block is published. It is the SHA-512 hash [RFC6234] over the derived zone key.

6.2. The Records Block

GNS records are grouped by their labels and published as a single block in the storage. The grouped record sets MAY be paired with any number of supplemental records. Supplemental records MUST have the supplemental flag set (See Section 5). The contained resource records are encrypted using a symmetric encryption scheme. A GNS implementation publish RRBLOCKs in accordance to the properties and recommendations of the underlying storage. This may include a periodic refresh operation to ensure the availability of the published RRBLOCKs. The GNS RRBLOCK wire format is illustrated in Figure 18.

0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|          SIZE         |    ZONE TYPE          |
+-----+-----+-----+-----+-----+-----+-----+-----+
/                  ZONE KEY                     /
/                  (BLINDED)                    /
|                                               |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                   SIGNATURE                   |
/                                               /
/                                               /
|                                               |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                   EXPIRATION                  |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                    BDATA                      /
/                                               /
/                                               |
+-----+-----+-----+-----+-----+-----+-----+-----+
Figure 18

The RRBLOCK Wire Format.

SIZE
A 32-bit value containing the length of the block. While a 32-bit value is used, implementations MAY refuse to publish blocks beyond a certain size significantly below 4 GB.
ZONE TYPE
is the 32-bit ztype.
ZONE KEY
is the blinded zone key "ZKDF-Public(zk, label)" to be used to verify SIGNATURE. The length and format of the public key depends on the ztype.
SIGNATURE
The signature is computed over the EXPIRATION and BDATA fields as detailed in Figure 19. The length and format of the signature depends on the ztype. The signature is created using the Sign() function of the cryptosystem of the zone and the derived private key "ZKDF-Private(d, label)" (see Section 4).
EXPIRATION
Specifies when the RRBLOCK expires and the encrypted block SHOULD be removed from the storage and caches as it is likely stale. However, applications MAY continue to use non-expired individual records until they expire. The value MUST be set to the expiration time of the resource record contained within this block with the smallest expiration time. If a records block includes shadow records, then the maximum expiration time of all shadow records with matching type and the expiration times of the non-shadow records is considered. This is a 64-bit absolute date in microseconds since midnight (0 hour), January 1, 1970 UTC in network byte order.
BDATA
The encrypted RDATA. Its size is determined by the S-Encrypt() function of the ztype.

The signature over the public key covers a 32-bit pseudo header conceptually prefixed to the EXPIRATION and the BDATA fields. The wire format is illustrated in Figure 19.

0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|         SIZE          |       PURPOSE (0x0F)  |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                   EXPIRATION                  |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                    BDATA                      |
/                                               /
/                                               /
+-----+-----+-----+-----+-----+-----+-----+-----+
Figure 19

The Wire Format used for creating the signature of the RRBLOCK.

SIZE
A 32-bit value containing the length of the signed data in bytes in network byte order.
PURPOSE
A 32-bit signature purpose flag. The value of this field MUST be 15. The value is encoded in network byte order. It defines the context in which the signature is created so that it cannot be reused in other parts of the protocol including possible future extensions. The value of this field corresponds to an entry in the GANA "GNUnet Signature Purpose" registry Section 10.
EXPIRATION
Field as defined in the RRBLOCK message above.
BDATA
Field as defined in the RRBLOCK message above.

A symmetric encryption scheme is used to encrypt the resource records set RDATA into the BDATA field of a GNS RRBLOCK. The wire format of the RDATA is illustrated in Figure 20.

0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|                 EXPIRATION                    |
+-----+-----+-----+-----+-----+-----+-----+-----+
|    SIZE   |    FLAGS  |        TYPE           |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                      DATA                     /
/                                               /
/                                               /
+-----+-----+-----+-----+-----+-----+-----+-----+
|                   EXPIRATION                  |
+-----+-----+-----+-----+-----+-----+-----+-----+
|    SIZE   |    FLAGS  |        TYPE           |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                     DATA                      /
/                                               /
+-----+-----+-----+-----+-----+-----+-----+-----+
/                     PADDING                   /
/                                               /
Figure 20

The RDATA Wire Format.

EXPIRATION, SIZE, TYPE, FLAGS and DATA
These fields were defined in the resource record format in Section 5.
PADDING
When publishing an RDATA block, the implementation MUST ensure that the size of the RDATA is a power of two using the padding field. The field MUST be set to zero and MUST be ignored on receipt. As a special exception, record sets with (only) a zone delegation record type are never padded. Note that a record set with a delegation record MUST NOT contain other records. If other records are encountered, the whole record block MUST be discarded.

7. Name Resolution

Names in GNS are resolved by recursively querying the record storage. Recursive in this context means that a resolver does not provide intermediate results for a query. Instead, it MUST respond to a resolution request with either the requested resource record or an error message in case the resolution fails. In the following, we define how resolution is initiated and each iteration in the resolution is processed.

GNS resolution of a name must start in a given starting zone indicated using a zone key. Details on how the starting zone may be determined are discussed in Section 7.1.

The application MAY provide a desired record type to the resolver. The desired record type is used to guide processing. For example, if a zone delegation record type is requested, the resolution of the apex label in that zone must be skipped, as the desired record is already found. The resolver implementation MUST NOT filter results according to the desired record type. Filtering of record sets is typically done by the application.

7.1. Start Zones

The resolution of a GNS name starts in an initial start zone. The resolver may have one or more local start zones configured which point to local or remote zone keys. A resolver may also determine the start zone from the suffix of the name given for resolution, or using information retrieved out of band.

The governance model of any zone is at the sole discretion of the zone owner. However, the choice of start zone(s) is at the sole discretion of the local system administrator or user. This property addresses the issue of a single hierarchy with a centrally controlled root and the related issue of distribution and management of root servers in DNS (see [RFC8324], Section 3.10 and 3.12).

In the following, we give examples how a resolver SHOULD discover the start zone. The process given is not exhaustive and resolvers MAY supplement it with other mechanisms or ignore it if the particular application requires a different process.

GNS implementations MUST first try to interpret the top-level domain of a GNS name as a zone key representation (i.e. a zTLD). If the top-level domain can be converted to a valid ztype and zone key value, the resulting zone key is used as the start zone:

Example name: www.example.<zTLD>
=> Start zone: zk of type ztype
=> Name to resolve from start zone: www.example

In GNS, users MAY own and manage their own zones. Each local zone SHOULD be associated with a single GNS label, but users MAY choose to use longer names consisting of multiple labels. If the name of a locally managed zone matches the suffix of the name to be resolved, resolution MUST start from the respective local zone with the longest matching suffix:

Example name: www.example.org
Local zones:
fr = (d0,zk0)
org = (d1,zk1)
com = (d2,zk2)
...
=> Start zone: zk1
=> Name to resolve from start zone: www.example

Finally, additional "suffix-to-zone" mappings MAY be configured. Suffix to zone key mappings MUST be configurable through a local configuration file or database by the user or system administrator. The suffix MAY consist of multiple GNS labels concatenated with a ".". If multiple suffixes match the name to resolve, the longest matching suffix MUST be used. The suffix length of two results MUST NOT be equal. This indicates a misconfiguration and the implementation MUST return an error. If both a locally managed zone and a configuration entry exist for the same suffix, the locally managed zone MUST have priority.

Example name: www.example.org
Local suffix mappings:
org = zk0
example.org = zk1
example.com = zk2
...
=> Start zone: zk1
=> Name to resolve from start zone: www

7.2. Recursion

In each step of the recursive name resolution, there is an authoritative zone zk and a name to resolve. The name may be empty. Initially, the authoritative zone is the start zone. If the name is empty, it is interpreted as the apex label "@".

From here, the following steps are recursively executed, in order:

  1. Extract the right-most label from the name to look up.
  2. Calculate q using the label and zk as defined in Section 6.1.
  3. Perform a storage query GET(q) to retrieve the RRBLOCK.
  4. Verify and process the RRBLOCK and decrypt the BDATA contained in it as defined by its zone type (see also Section 6.2).

Upon receiving the RRBLOCK from the storage, as part of verifying the provided signature, the resolver MUST check that the SHA-512 hash of the derived authoritative zone key zk' from the RRBLOCK matches the query q and that the overall block is not yet expired. If the signature does not match or the block is expired, the RRBLOCK MUST be ignored and, if applicable, the storage lookup GET(q) MUST continue to look for other RRBLOCKs.

7.3. Record Processing

Record processing occurs once a well-formed block was decrypted. In record processing, only the valid records obtained are considered. To filter records by validity, the resolver MUST at least check the expiration time and the FLAGS of the respective record. In particular, FLAGS may exclude shadow and supplemental records from being considered. If the resolver encounters a record with the CRITICAL flag set and does not support the record type the resolution MUST be aborted and an error MUST be returned. The information that the critical record could not be processed SHOULD be returned in the error description. The implementation MAY choose not to return the reason for the failure, merely complicating troubleshooting for the user. The next steps depend on the context of the name we are trying to resolve:

  • Case 1: If the filtered record set consists of a single REDIRECT record, the remainder of the name is prepended to the REDIRECT data and the recursion is started again from the resulting name. Details are described in Section 7.3.1.
  • Case 2: If the filtered record set consists exclusively of one or more GNS2DNS records resolution continues with DNS. Details are described in Section 7.3.2.
  • Case 3: If the remainder of the name to be resolved is of the format "_SERVICE._PROTO" and the record set contains one or more matching BOX records, the records in the BOX records are the final result and the recursion is concluded as described in Section 7.3.3.
  • Case 4: If the current record set consist of a single delegation record, resolution of the remainder of the name is delegated to the target zone as described in Section 7.3.4.
  • Case 5: If the remainder of the name to resolve is empty the record set (including supplemental records) is the final result and the recursion is concluded.
  • Otherwise, resolution fails and the resolver MUST return an empty record set.

7.3.1. REDIRECT

If the remaining name is empty and the desired record type is REDIRECT, in which case the resolution concludes with the REDIRECT record. If the redirect name ends in ".+", resolution continues in GNS with the new name in the current zone. Otherwise, the resulting name is resolved via the default operating system name resolution process. This may in turn trigger a GNS name resolution process depending on the system configuration. In case resolution continues in DNS, the name MUST first be converted to an IDNA punycode representation [RFC5891].

In order to prevent infinite loops, the resolver MUST implement loop detections or limit the number of recursive resolution steps. The loop detection MUST be effective even if a REDIRECT found in GNS triggers subsequent GNS lookups via the default operating system name resolution process.

7.3.2. GNS2DNS

When a resolver encounters one or more GNS2DNS records and the remaining name is empty and the desired record type is GNS2DNS, the GNS2DNS records are returned.

Otherwise, it is expected that the resolver first resolves the IP addresses of the specified DNS name servers. The DNS name may have to be converted to an IDNA punycode representation [RFC5891] for resolution in DNS. GNS2DNS records MAY contain numeric IPv4 or IPv6 addresses, allowing the resolver to skip this step. The DNS server names may themselves be names in GNS or DNS. If the DNS server name ends in ".+", the rest of the name is to be interpreted relative to the zone of the GNS2DNS record. If the DNS server name ends in a label representation of a zone key, the DNS server name is to be resolved against the GNS zone zk.

Multiple GNS2DNS records may be stored under the same label, in which case the resolver MUST try all of them. The resolver MAY try them in any order or even in parallel. If multiple GNS2DNS records are present, the DNS name MUST be identical for all of them, if not the resolution fails and an appropriate error is SHOULD be returned to the application.

If there are DNSSEC DS records or any other records used to secure the connection with the DNS servers stored under the label, the DNS resolver SHOULD use them to secure the connection with the DNS server.

Once the IP addresses of the DNS servers have been determined, the DNS name from the GNS2DNS record is appended to the remainder of the name to be resolved, and resolved by querying the DNS name server(s). As the DNS servers specified are possibly authoritative DNS servers, the GNS resolver MUST support recursive DNS resolution and MUST NOT delegate this to the authoritative DNS servers. The first successful recursive name resolution result is returned to the application. In addition, the resolver SHOULD return the queried DNS name as a supplemental LEHO record (see Section 5.3.1) with a relative expiration time of one hour.

Once the transition from GNS into DNS is made through a GNS2DNS record, there is no "going back". The (possibly recursive) resolution of the DNS name MUST NOT delegate back into GNS and should only follow the DNS specifications. For example, names contained in DNS CNAME records MUST NOT be interpreted as GNS names.

GNS resolvers SHOULD offer a configuration option to disable DNS processing to avoid information leakage and provide a consistent security profile for all name resolutions. Such resolvers would return an empty record set upon encountering a GNS2DNS record during the recursion. However, if GNS2DNS records are encountered in the record set for the apex label and a GNS2DNS record is explicitly requested by the application, such records MUST still be returned, even if DNS support is disabled by the GNS resolver configuration.

7.3.3. BOX

When a BOX record is received, a GNS resolver must unbox it if the name to be resolved continues with "_SERVICE._PROTO". Otherwise, the BOX record is to be left untouched. This way, TLSA (and SRV) records do not require a separate network request, and TLSA records become inseparable from the corresponding address records.

7.3.4. Zone Delegation Records

When the resolver encounters a record of a supported zone delegation record type (such as PKEY or EDKEY) and the remainder of the name is not empty, resolution continues recursively with the remainder of the name in the GNS zone specified in the delegation record. Implementations MUST NOT allow multiple different zone delegations under a single label. Implementations MAY support any subset of ztypes. Handling of Implementations MUST NOT process zone delegation for the apex label "@". Upon encountering a zone delegation record under this label, resolution fails and an error MUST be returned. The implementation MAY choose not to return the reason for the failure, merely impacting troubleshooting information for the user.

If the remainder of the name to resolve is empty and we have received a record set containing only a single delegation record, the recursion is continued with the record value as authoritative zone and the apex label "@" as remaining name. Except in the case where the desired record type as specified by the application is equal to the ztype, in which case the delegation record is returned.

7.3.5. NICK

NICK records are only relevant to the recursive resolver if the record set in question is the final result which is to be returned to the application. The encountered NICK records may either be supplemental (see Section 5) or non-supplemental. If the NICK record is supplemental, the resolver only returns the record set if one of the non-supplemental records matches the queried record type. It is possible that one record set contains both supplemental and non-supplemental NICK records.

The differentiation between a supplemental and non-supplemental NICK record allows the application to match the record to the authoritative zone. Consider the following example:

Query: alice.example (type=A)
Result:
A: 192.0.2.1
NICK: eve (non-Supplemental)

In this example, the returned NICK record is non-supplemental. For the application, this means that the NICK belongs to the zone "alice.example" and is published under the apex label along with an A record. The NICK record should be interpreted as: The zone defined by "alice.example" wants to be referred to as "eve". In contrast, consider the following:

Query: alice.example (type=AAAA)
Result:
AAAA: 2001:DB8::1
NICK: john (Supplemental)

In this case, the NICK record is marked as supplemental. This means that the NICK record belongs to the zone "example" and is published under the label "alice" along with an A record. The NICK record should be interpreted as: The zone defined by "example" wants to be referred to as "john". This distinction is likely useful for other records published as supplemental.

8. Internationalization and Character Encoding

All labels in GNS are encoded in UTF-8 [RFC3629]. Labels MUST be canonicalized using Normalization Form C (NFC) [Unicode-UAX15]. This does not include any DNS names found in DNS records, such as CNAME records, which are internationalized through the IDNA specifications [RFC5890].

9. Security and Privacy Considerations

9.1. Availability

In order to ensure availability of records beyond their absolute expiration times, implementations MAY allow to locally define relative expiration time values of records. Records can then be published recurringly with updated absolute expiration times by the implementation.

Implementations MAY allow users to manage private records in their zones that are not published in the storage. Private records are considered just like regular records when resolving labels in local zones, but their data is completely unavailable to non-local users.

9.2. Agility

The security of cryptographic systems depends on both the strength of the cryptographic algorithms chosen and the strength of the keys used with those algorithms. The security also depends on the engineering of the protocol used by the system to ensure that there are no non-cryptographic ways to bypass the security of the overall system. This is why developers of applications managing GNS zones SHOULD select a default ztype considered secure at the time of releasing the software. For applications targeting end users that are not expected to understand cryptography, the application developer MUST NOT leave the ztype selection of new zones to end users.

This document concerns itself with the selection of cryptographic algorithms used in GNS. The algorithms identified in this document are not known to be broken (in the cryptographic sense) at the current time, and cryptographic research so far leads us to believe that they are likely to remain secure into the foreseeable future. However, this is not necessarily forever, and it is expected that new revisions of this document will be issued from time to time to reflect the current best practices in this area.

In terms of crypto-agility, whenever the need for an updated cryptographic scheme arises to, for example, replace ECDSA over Ed25519 for PKEY records it may simply be introduced through a new record type. Such a new record type may then replace the delegation record type for future records. The old record type remains and zones can iteratively migrate to the updated zone keys. To ensure that implementations correctly generate an error message when encountering a ztype that they do not support, current and future delegation records must always have the CRITICAL flag set.

9.3. Cryptography

GNS PKEY zone keys use ECDSA over Ed25519. This is an unconventional choice, as ECDSA is usually used with other curves. However, traditional ECDSA curves are problematic for a range of reasons described in the Curve25519 and EdDSA papers. Using EdDSA directly is also not possible, as a hash function is used on the private key which destroys the linearity that the GNU Name System depends upon. We are not aware of anyone suggesting that using Ed25519 instead of another common curve of similar size would lower the security of ECDSA. GNS uses 256-bit curves because that way the encoded (public) keys fit into a single DNS label, which is good for usability.

In order to ensure ciphertext indistinguishability, care must be taken with respect to the initialization vector in the counter block. In our design, the IV always includes the expiration time of the record block. When applications store records with relative expiration times, monotonicity is implicitly ensured because each time a block is published into the storage, its IV is unique as the expiration time is calculated dynamically and increases monotonically with the system time. Still, an implementation MUST ensure that when relative expiration times are decreased, the expiration time of the next record block MUST be after the last published block. For records where an absolute expiration time is used, the implementation MUST ensure that the expiration time is always increased when the record data changes. For example, the expiration time on the wire may be increased by a single microsecond even if the user did not request a change. In case of deletion of all resource records under a label, the implementation MUST keep track of the last absolute expiration time of the last published resource block. Implementations MAY use a PADDING record as a tombstone that preserves the last absolute expiration time, but then MUST take care to not publish a block with just a PADDING record. When new records are added under this label later, the implementation MUST ensure that the expiration times are after the last published block. Finally, in order to ensure monotonically increasing expiration times the implementation MUST keep a local record of the last time obtained from the system clock, so as to construct a monotonic clock in case the system clock jumps backwards.

9.4. Abuse Mitigation

GNS names are UTF-8 strings. Consequently, GNS faces similar issues with respect to name spoofing as DNS does for internationalized domain names. In DNS, attackers may register similar sounding or looking names (see above) in order to execute phishing attacks. GNS zone administrators must take into account this attack vector and incorporate rules in order to mitigate it.

Further, DNS can be used to combat illegal content on the internet by having the respective domains seized by authorities. However, the same mechanisms can also be abused in order to impose state censorship, which is one of the motivations behind GNS. Hence, such a seizure is, by design, difficult to impossible in GNS.

9.5. Zone Management

In GNS, zone administrators need to manage and protect their zone keys. Once a zone key is lost, it cannot be recovered or revoked. Revocation messages may be pre-calculated if revocation is required in case a zone key is lost. Zone administrators, and for GNS this includes end-users, are required to responsibly and diligently protect their cryptographic keys. GNS supports offline signing of records.

Similarly, users are required to manage their local start zone configuration. In order to ensure integrity and availability or names, users must ensure that their local start zone information is not compromised or outdated. It can be expected that the processing of zone revocations and an initial start zone is provided with a GNS implementation ("drop shipping"). Shipping an initial start zone with an entry for the root (".") effectively establishes a root zone. Extension and customization of the zone is at the full discretion of the user.

While implementations following this specification will be interoperable, if two implementations connect to different storages they are mutually unreachable. This may lead to a state where a record may exist in the global namespace for a particular name, but the implementation is not communicating with the storage and is hence unable to resolve it. This situation is similar to a split-horizon DNS configuration. Which storages are implemented usually depends on the application it is built for. The storage used will most likely depend on the specific application context using GNS resolution. For example, one application may be the resolution of hidden services within the Tor network, which may suggest using Tor routers for storage. Implementations of "aggregated" storages are conceivable, but are expected to be the exception.

9.6. Impact of DHTs as Underlying Storage

This document does not specify the properties of the underlying storage which is required by any GNS implementation. It is important to note that the properties of the underlying storage are directly inherited by the GNS implementation. This includes both security as well as other non-functional properties such as scalability and performance. Implementers should take great care when selecting or implementing a DHT for use as storage in a GNS implementation. DHTs with reasonable security and performance properties exist [R5N]. It should also be taken into consideration that GNS implementations which build upon different DHT overlays are unlikely to be interoperable with each other.

9.7. Revocations

Zone administrators are advised to pre-generate zone revocations and to securely store the revocation information in case the zone key is lost, compromised or replaced in the future. Pre-calculated revocations may become invalid due to expirations or protocol changes such as epoch adjustments. Consequently, implementers and users must take precautions in order to manage revocations accordingly.

Revocation payloads do NOT include a 'new' key for key replacement. Inclusion of such a key would have two major disadvantages:

  1. If a revocation is published after a private key was compromised, allowing key replacement would be dangerous: if an adversary took over the private key, the adversary could then broadcast a revocation with a key replacement. For the replacement, the compromised owner would have no chance to issue even a revocation. Thus, allowing a revocation message to replace a private key makes dealing with key compromise situations worse.
  2. Sometimes, key revocations are used with the objective of changing cryptosystems. Migration to another cryptosystem by replacing keys via a revocation message would only be secure as long as both cryptosystems are still secure against forgery. Such a planned, non-emergency migration to another cryptosystem should be done by running zones for both cipher systems in parallel for a while. The migration would conclude by revoking the legacy zone key only once it is deemed no longer secure, and hopefully after most users have migrated to the replacement.

9.8. Label Guessing

Record blocks are published in encrypted form using keys derived from the zone key and record label. Zone administrators should carefully consider if the label and zone key may be public or if those should be used and considered as a shared secret. Unlike zone keys, labels can also be guessed by an attacker in the network observing queries and responses. Given a known and targeted zone key, the use of well known or easily guessable labels effectively result in general disclosure of the records to the public. If the labels and hence the records should be kept secret except to those knowing a secret label and the zone in which to look, the label must be chosen accordingly. It is recommended to then use a label with sufficient entropy as to prevent guessing attacks.

It should be noted that this attack on labels only applies if the zone key is somehow disclosed to the adversary. GNS itself does not disclose it during a lookup or when resource records are published as the zone keys are blinded beforehand. However, zone keys do become public during revocation.

10. GANA Considerations

GANA [GANA] manages the "GNU Name System Record Types" registry. Each entry has the following format:

The registration policy for this registry is "First Come First Served". This policy is modeled on that described in [RFC8126], and describes the actions taken by GANA:

Adding new records is possible after expert review, using a first-come-first-served policy for unique name allocation. Experts are responsible to ensure that the chosen "Name" is appropriate for the record type. The registry will assign a unique number for the entry.

The current contact(s) for expert review are reachable at gns-registry@gnunet.org.

Any request MUST contain a unique name and a point of contact. The contact information MAY be added to the registry given the consent of the requester. The request MAY optionally also contain relevant references as well as a descriptive comment as defined above.

GANA is requested to populate this registry as listed in Figure 21.

Number | Name    | Contact | References | Comment
-------+---------+---------+------------+-------------------------
65536  | PKEY    | N/A     | [This.I-D] | GNS zone delegation (PKEY)
65537  | NICK    | N/A     | [This.I-D] | GNS zone nickname
65538  | LEHO    | N/A     | [This.I-D] | GNS legacy hostname
65540  | GNS2DNS | N/A     | [This.I-D] | Delegation to DNS
65541  | BOX     | N/A     | [This.I-D] | Boxed records
65551  | REDIRECT| N/A     | [This.I-D] | Redirection record.
65556  | EDKEY   | N/A     | [This.I-D] | GNS zone delegation (EDKEY)
Figure 21

The GANA Resource Record Registry.

GANA is requested to amend the "GNUnet Signature Purpose" registry as illustrated in Figure 22.

Purpose | Name            | References | Comment
--------+-----------------+------------+--------------------------
  3     | GNS_REVOCATION  | [This.I-D] | GNS zone key revocation
 15     | GNS_RECORD_SIGN | [This.I-D] | GNS record set signature
Figure 22

Requested Changes in the GANA GNUnet Signature Purpose Registry.

11. IANA Considerations

This document makes no requests for IANA action. This section may be removed on publication as an RFC.

12. Implementation and Deployment Status

There are two implementations conforming to this specification written in C and Go, respectively. The C implementation as part of GNUnet [GNUnetGNS] represents the original and reference implementation. The Go implementation [GoGNS] demonstrates how two implementations of GNS are interoperable given that they are built on top of the same underlying DHT storage.

Currently, the GNUnet peer-to-peer network [GNUnet] is an active deployment of GNS on top of its [R5N] DHT. The [GoGNS] implementation uses this deployment by building on top of the GNUnet DHT services available on any GNUnet peer. It shows how GNS implementations can attach to this existing deployment and participate in name resolution as well as zone publication.

The self-sovereign identity system re:claimID [reclaim] is using GNS in order to selectively share identity attributes and attestations with third parties.

The Ascension tool [Ascension] facilitates the migration of DNS zones to GNS zones by translating information retrieved from a DNS zone transfer into a GNS zone.

13. Acknowledgements

The authors thank D. J. Bernstein, A. Farrel and S. Bortzmeyer for their insightful reviews. We thank NLnet and NGI DISCOVERY for funding work on the GNU Name System.

14. Normative References

[RFC1034]
Mockapetris, P., "Domain names - concepts and facilities", STD 13, RFC 1034, DOI 10.17487/RFC1034, , <https://www.rfc-editor.org/info/rfc1034>.
[RFC1035]
Mockapetris, P., "Domain names - implementation and specification", STD 13, RFC 1035, DOI 10.17487/RFC1035, , <https://www.rfc-editor.org/info/rfc1035>.
[RFC2782]
Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for specifying the location of services (DNS SRV)", RFC 2782, DOI 10.17487/RFC2782, , <https://www.rfc-editor.org/info/rfc2782>.
[RFC2119]
Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <https://www.rfc-editor.org/info/rfc2119>.
[RFC3629]
Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, , <https://www.rfc-editor.org/info/rfc3629>.
[RFC3686]
Housley, R., "Using Advanced Encryption Standard (AES) Counter Mode With IPsec Encapsulating Security Payload (ESP)", RFC 3686, DOI 10.17487/RFC3686, , <https://www.rfc-editor.org/info/rfc3686>.
[RFC3826]
Blumenthal, U., Maino, F., and K. McCloghrie, "The Advanced Encryption Standard (AES) Cipher Algorithm in the SNMP User-based Security Model", RFC 3826, DOI 10.17487/RFC3826, , <https://www.rfc-editor.org/info/rfc3826>.
[RFC5237]
Arkko, J. and S. Bradner, "IANA Allocation Guidelines for the Protocol Field", BCP 37, RFC 5237, DOI 10.17487/RFC5237, , <https://www.rfc-editor.org/info/rfc5237>.
[RFC5869]
Krawczyk, H. and P. Eronen, "HMAC-based Extract-and-Expand Key Derivation Function (HKDF)", RFC 5869, DOI 10.17487/RFC5869, , <https://www.rfc-editor.org/info/rfc5869>.
[RFC5890]
Klensin, J., "Internationalized Domain Names for Applications (IDNA): Definitions and Document Framework", RFC 5890, DOI 10.17487/RFC5890, , <https://www.rfc-editor.org/info/rfc5890>.
[RFC5891]
Klensin, J., "Internationalized Domain Names in Applications (IDNA): Protocol", RFC 5891, DOI 10.17487/RFC5891, , <https://www.rfc-editor.org/info/rfc5891>.
[RFC6234]
Eastlake 3rd, D. and T. Hansen, "US Secure Hash Algorithms (SHA and SHA-based HMAC and HKDF)", RFC 6234, DOI 10.17487/RFC6234, , <https://www.rfc-editor.org/info/rfc6234>.
[RFC6895]
Eastlake 3rd, D., "Domain Name System (DNS) IANA Considerations", BCP 42, RFC 6895, DOI 10.17487/RFC6895, , <https://www.rfc-editor.org/info/rfc6895>.
[RFC6979]
Pornin, T., "Deterministic Usage of the Digital Signature Algorithm (DSA) and Elliptic Curve Digital Signature Algorithm (ECDSA)", RFC 6979, DOI 10.17487/RFC6979, , <https://www.rfc-editor.org/info/rfc6979>.
[RFC7748]
Langley, A., Hamburg, M., and S. Turner, "Elliptic Curves for Security", RFC 7748, DOI 10.17487/RFC7748, , <https://www.rfc-editor.org/info/rfc7748>.
[RFC8032]
Josefsson, S. and I. Liusvaara, "Edwards-Curve Digital Signature Algorithm (EdDSA)", RFC 8032, DOI 10.17487/RFC8032, , <https://www.rfc-editor.org/info/rfc8032>.
[RFC8126]
Cotton, M., Leiba, B., and T. Narten, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 8126, DOI 10.17487/RFC8126, , <https://www.rfc-editor.org/info/rfc8126>.
[RFC8174]
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, , <https://www.rfc-editor.org/info/rfc8174>.
[RFC8499]
Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS Terminology", BCP 219, RFC 8499, DOI 10.17487/RFC8499, , <https://www.rfc-editor.org/info/rfc8499>.
[RFC9106]
Biryukov, A., Dinu, D., Khovratovich, D., and S. Josefsson, "Argon2 Memory-Hard Function for Password Hashing and Proof-of-Work Applications", RFC 9106, DOI 10.17487/RFC9106, , <https://www.rfc-editor.org/info/rfc9106>.
[GANA]
GNUnet e.V., "GNUnet Assigned Numbers Authority (GANA)", , <https://gana.gnunet.org/>.
[MODES]
Dworkin, M., "Recommendation for Block Cipher Modes of Operation: Methods and Techniques", , <https://doi.org/10.6028/NIST.SP.800-38A>.
[CrockfordB32]
Douglas, D., "Base32", , <https://www.crockford.com/base32.html>.
[XSalsa20]
Bernstein, D., "Extending the Salsa20 nonce", , <https://cr.yp.to/snuffle/xsalsa-20110204.pdf>.
[Unicode-UAX15]
Consortium, T. U., "Unicode Standard Annex #15: Unicode Normalization Forms, Revision 31", , <http://www.unicode.org/reports/tr15/tr15-31.html>.

15. Informative References

[RFC4033]
Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose, "DNS Security Introduction and Requirements", RFC 4033, DOI 10.17487/RFC4033, , <https://www.rfc-editor.org/info/rfc4033>.
[RFC7363]
Maenpaa, J. and G. Camarillo, "Self-Tuning Distributed Hash Table (DHT) for REsource LOcation And Discovery (RELOAD)", RFC 7363, DOI 10.17487/RFC7363, , <https://www.rfc-editor.org/info/rfc7363>.
[RFC8324]
Klensin, J., "DNS Privacy, Authorization, Special Uses, Encoding, Characters, Matching, and Root Structure: Time for Another Look?", RFC 8324, DOI 10.17487/RFC8324, , <https://www.rfc-editor.org/info/rfc8324>.
[Tor224]
Goulet, D., Kadianakis, G., and N. Mathewson, "Next-Generation Hidden Services in Tor", , <https://gitweb.torproject.org/torspec.git/tree/proposals/224-rend-spec-ng.txt#n2135>.
[SDSI]
Rivest, R. and B. Lampson, "SDSI - A Simple Distributed Security Infrastructure", , <http://people.csail.mit.edu/rivest/Sdsi10.ps>.
[Kademlia]
Maymounkov, P. and D. Mazieres, "Kademlia: A peer-to-peer information system based on the xor metric.", , <http://css.csail.mit.edu/6.824/2014/papers/kademlia.pdf>.
[ed25519]
Bernstein, D., Duif, N., Lange, T., Schwabe, P., and B. Yang, "High-Speed High-Security Signatures", , <http://link.springer.com/chapter/10.1007/978-3-642-23951-9_9>.
[GNS]
Wachs, M., Schanzenbach, M., and C. Grothoff, "A Censorship-Resistant, Privacy-Enhancing and Fully Decentralized Name System", , <https://sci-hub.st/10.1007/978-3-319-12280-9_9>.
[R5N]
Evans, N. S. and C. Grothoff, "R5N: Randomized recursive routing for restricted-route networks", , <https://sci-hub.st/10.1109/ICNSS.2011.6060022>.
[SecureNS]
Grothoff, C., Wachs, M., Ermert, M., and J. Appelbaum, "Towards secure name resolution on the Internet", , <https://sci-hub.st/https://doi.org/10.1016/j.cose.2018.01.018>.
[GNUnetGNS]
GNUnet e.V., "The GNUnet GNS Implementation", <https://git.gnunet.org/gnunet.git/tree/src/gns>.
[Ascension]
GNUnet e.V., "The Ascension Implementation", <https://git.gnunet.org/ascension.git>.
[GNUnet]
GNUnet e.V., "The GNUnet Project", <https://gnunet.org>.
[reclaim]
GNUnet e.V., "The GNUnet Project", <https://reclaim.gnunet.org>.
[GoGNS]
Fix, B., "The Go GNS Implementation", <https://github.com/bfix/gnunet-go/tree/master/src/gnunet/service/gns>.

Appendix A. Base32GNS

This table defines the encode symbol and decode symbol for a given symbol value. It can be used to implement the encoding by reading it as: A character "A" or "a" is decoded to a 5 bit value 10 when decoding. A 5 bit block with a value of 18 is encoded to the character "J" when encoding. If the bit length of the byte string to encode is not a multiple of 5 it is padded to the next multiple with zeroes. In order to further increase tolerance for failures in character recognition, the letter "U" MUST be decoded to the same value as the letter "V" in Base32GNS.

Symbol      Decode            Encode
Value       Symbol            Symbol
0           0 O o             0
1           1 I i L l         1
2           2                 2
3           3                 3
4           4                 4
5           5                 5
6           6                 6
7           7                 7
8           8                 8
9           9                 9
10          A a               A
11          B b               B
12          C c               C
13          D d               D
14          E e               E
15          F f               F
16          G g               G
17          H h               H
18          J j               J
19          K k               K
20          M m               M
21          N n               N
22          P p               P
23          Q q               Q
24          R r               R
25          S s               S
26          T t               T
27          V v U u           V
28          W w               W
29          X x               X
30          Y y               Y
31          Z z               Z
Figure 23

The Base32GNS Alphabet Including the Additional U Encode Symbol.

Appendix B. Test Vectors

The following are test vectors for the Base32GNS encoding used for zTLDs. The strings are encoded without the zero terminator.


Base32GNS-Encode:
  Input string: "Hello World"
  Output string: "91JPRV3F41BPYWKCCG"

  Input bytes: 474e55204e616d652053797374656d
  Output string: "8X75A82EC5PPA82KF5SQ8SBD"

Base32GNS-Decode:
  Input string: "91JPRV3F41BPYWKCCG"
  Output string: "Hello World"

  Input string: "91JPRU3F41BPYWKCCG"
  Output string: "Hello World"

The following represents a test vector for a record set with a DNS record of type "A" as well as a GNS record of type "PKEY" under the label "test".


Zone private key (d, big-endian):
50d7b652a4efeadf
f37396909785e595
2171a02178c8e7d4
50fa907925fafd98

Zone identifier (ztype|zkey):
00010000677c477d
2d93097c85b195c6
f96d84ff61f5982c
2c4fe02d5a11fedf
b0c2901f

Encoded zone identifier (zkl = zTLD):
000G0037FH3QTBCK15Y8BCCNRVWPV17ZC7TSGB1C9ZG2TPGHZVFV1GMG3W

Label: testdelegation
RRCOUNT: 1

Record #0
EXPIRATION: 2463385894000000
DATA_SIZE: 36
TYPE: 65536
FLAGS: 01000000

DATA:
0001000021e3b30f
f93bc6d35ac8c6e0
e13afdff794cb7b4
4bbbc748d259d0a0
284dbe84

RDATA:
0008c06fb9281580
0024000100010000
0001000021e3b30f
f93bc6d35ac8c6e0
e13afdff794cb7b4
4bbbc748d259d0a0
284dbe84

Encryption NONCE|EXPIRATION|BLOCK COUNTER:
e90a00610008c06f
b928158000000001

Encryption key (K):
864e7138eae7fd91
a30136899c132b23
acebdb2cef43cb19
f6bf55b67db9b3b3

Storage key (q):
4adc67c5ecee9f76
986abd71c2224a3d
ce2e917026c9a09d
fd44cef3d20f55a2
7332725a6c8afbbb
b0f7ec9af1cc4264
1299406b04fd9b5b
5791f86c4b08d5f4

BDATA:
41dc7b5f2176ba59
199cafb9e3c82579
71b21ccb6de51d38
bd2a21e9322c6af8
4243e8de876b5b76
37462e79b2c162db
4014d5c9

RRBLOCK:
000000a400010000
182bb636eda79f79
5711bc2708adbb24
2a60446ad3c30803
121d03d348b7ceb6
01a968a5eac3cb95
ed58c1c5386f4ab6
539edd8099b4893a
be83f242115e3e35
03965dc924a6001a
e94ecab9b2f25c4c
6fdc7ffbe9f3b2a2
854b321b1d7ea9ab
0008c06fb9281580
41dc7b5f2176ba59
199cafb9e3c82579
71b21ccb6de51d38
bd2a21e9322c6af8
4243e8de876b5b76
37462e79b2c162db
4014d5c9

Zone private key (d, big-endian):
50d7b652a4efeadf
f37396909785e595
2171a02178c8e7d4
50fa907925fafd98

Zone identifier (ztype|zkey):
00010000677c477d
2d93097c85b195c6
f96d84ff61f5982c
2c4fe02d5a11fedf
b0c2901f

Encoded zone identifier (zkl = zTLD):
000G0037FH3QTBCK15Y8BCCNRVWPV17ZC7TSGB1C9ZG2TPGHZVFV1GMG3W

Label: testset
RRCOUNT: 3

Record #0
EXPIRATION: 2463385894000000
DATA_SIZE: 16
TYPE: 28
FLAGS: 00000000

DATA:
0000000000000000
00000000deadbeef

Record #1
EXPIRATION: 49556645701000000
DATA_SIZE: 9
TYPE: 65537
FLAGS: 00800000

DATA:
536f6d65206e6963
6b

Record #2
EXPIRATION: 6091321688
DATA_SIZE: 11
TYPE: 16
FLAGS: 04400000

DATA:
48656c6c6f20576f
726c64

RDATA:
0008c06fb9281580
001000000000001c
0000000000000000
00000000deadbeef
00b00f81b7449b40
0009800000010001
536f6d65206e6963
6b000000016b1231
58000b4004000000
1048656c6c6f2057
6f726c6400000000
0000000000000000
0000000000000000
0000000000000000
0000000000000000
0000000000000000

Encryption NONCE|EXPIRATION|BLOCK COUNTER:
4edb104e0005d78a
44e4e6c800000001

Encryption key (K):
4a7d3f21f67c377e
ad2cb255b6c05930
6287e78caeff4c80
f08e1df327900d21

Storage key (q):
e8f9a842256e825b
f40e802ab2a81a3c
31d621100b4adec0
3c152e22cdbcab0d
d5dde37815887f74
950b22179269e6b3
2b75928dd80111de
3e12eca5517ae246

BDATA:
a6b26ac00e485ddd
26e8db68e3eaba01
b5760ae197f70e28
39cc9e4ac40668f4
61285e42d8e7c397
cfc90e8042106666
9a0506edccfacb1b
520103c2a68eb06d
770c7bd65e6810c3
88e192cc313f924b
ffe67ce114694f20
03d851c7fe5623b2
5eb0fad6bbdf917b
e7eac3a9ec795dd4
a9c8b4c683896b2c
69d4d5ae8dafd93a

RRBLOCK:
000000f000010000
d84c242613691d2f
2150f55b89ee03ca
0b13f9fa6905eb17
acedcbc55518b8aa
042c1e6e6e3aa52a
6538a91fd3d5e9cd
987edb1106f3f864
fea111382f5a0a42
0b954ccb4dc6e9e1
3cbec65e7ae021ec
7c4f7830aa158423
da439dc17fee7586
0005d78a44e4e6c8
a6b26ac00e485ddd
26e8db68e3eaba01
b5760ae197f70e28
39cc9e4ac40668f4
61285e42d8e7c397
cfc90e8042106666
9a0506edccfacb1b
520103c2a68eb06d
770c7bd65e6810c3
88e192cc313f924b
ffe67ce114694f20
03d851c7fe5623b2
5eb0fad6bbdf917b
e7eac3a9ec795dd4
a9c8b4c683896b2c
69d4d5ae8dafd93a

The following represents a test vector for a record set with a DNS record of type "A" as well as a GNS record of type "EDKEY" under the label "test".


Zone private key (d):
5af7020ee1916032
8832352bbc6a68a8
d71a7cbe1b929969
a7c66d415a0d8f65

Zone identifier (ztype|zkey):
000100143cf4b924
032022f0dc505814
53b85d93b047b63d
446c5845cb48445d
db96688f

Encoded zone identifier (zkl = zTLD):
000G051WYJWJ80S04BRDRM2R2H9VGQCKP13VCFA4DHC4BJT88HEXQ5K8HW

Label: testdelegation
RRCOUNT: 1

Record #0
EXPIRATION: 2463385894000000
DATA_SIZE: 36
TYPE: 65536
FLAGS: 01000000

DATA:
0001000021e3b30f
f93bc6d35ac8c6e0
e13afdff794cb7b4
4bbbc748d259d0a0
284dbe84

RDATA:
0008c06fb9281580
0024000100010000
0001000021e3b30f
f93bc6d35ac8c6e0
e13afdff794cb7b4
4bbbc748d259d0a0
284dbe84

Encryption NONCE|EXPIRATION:
98132ea86859d35c
88bfd317fa991bcb
0008c06fb9281580

Encryption key (K):
85c429a9567aa633
411a9691e9094c45
281672be586034aa
e4a2a2cc716159e2

Storage key (q):
abaabac0e1249459
75988395aac0241e
5559c41c4074e255
7b9fe6d154b614fb
cdd47fc7f51d786d
c2e0b1ece76037c0
a1578c384ec61d44
5636a94e880329e9

BDATA:
7d9ecea3c19ef07b
0db1fab44c5e4477
6ea8d8894e904a0c
35ed1c5c2ff2ed93
bd204b3fcae98192
fad94afbc5bba3a6
de538c01c7e1f65e
2a883cc068c02109
7afd7330

RRBLOCK:
000000b400010014
9bf233198c6d53bb
dbac495cabd91049
a684af3f4051baca
b0dcf21c8cf27a1a
69ac3485946796d1
e31837f569d71e06
e79c4777ab9c41fa
29cdd198464aac3d
aaeea2c192eb6e71
1d0dc7bb76994eca
ab837e402ba2c994
4df155b6e96fdf0a
0008c06fb9281580
7d9ecea3c19ef07b
0db1fab44c5e4477
6ea8d8894e904a0c
35ed1c5c2ff2ed93
bd204b3fcae98192
fad94afbc5bba3a6
de538c01c7e1f65e
2a883cc068c02109
7afd7330

Zone private key (d):
5af7020ee1916032
8832352bbc6a68a8
d71a7cbe1b929969
a7c66d415a0d8f65

Zone identifier (ztype|zkey):
000100143cf4b924
032022f0dc505814
53b85d93b047b63d
446c5845cb48445d
db96688f

Encoded zone identifier (zkl = zTLD):
000G051WYJWJ80S04BRDRM2R2H9VGQCKP13VCFA4DHC4BJT88HEXQ5K8HW

Label: testset
RRCOUNT: 3

Record #0
EXPIRATION: 2463385894000000
DATA_SIZE: 16
TYPE: 28
FLAGS: 00000000

DATA:
0000000000000000
00000000deadbeef

Record #1
EXPIRATION: 49556645701000000
DATA_SIZE: 9
TYPE: 65537
FLAGS: 00800000

DATA:
536f6d65206e6963
6b

Record #2
EXPIRATION: 6091321688
DATA_SIZE: 11
TYPE: 16
FLAGS: 04400000

DATA:
48656c6c6f20576f
726c64

RDATA:
0008c06fb9281580
001000000000001c
0000000000000000
00000000deadbeef
00b00f81b7449b40
0009800000010001
536f6d65206e6963
6b000000016b1231
58000b4004000000
1048656c6c6f2057
6f726c6400000000
0000000000000000
0000000000000000
0000000000000000
0000000000000000
0000000000000000

Encryption NONCE|EXPIRATION:
0a27e1f82798d680
4285c81ef29391f9
0005d78a44e4ff82

Encryption key (K):
227730f8c97f94ab
5de3645aa731be24
769f04cacb88312d
e8e5102909693488

Storage key (q):
60c6e5b3442eb232
837e70205f26ca16
539f1354692fbeb3
05541efd0e3216cc
9373d3e2c6f8fa1d
1e49cfd9c19cb654
0621377eb989461c
f09676309323b000

BDATA:
dfc0aa69cee85288
434b48d487ed3911
5118213b7b2efe73
9067c6f6c0e83d59
7d9288b018e73b66
264ee8587d026c60
bd2ff2e3d50a7d49
1b53803c8ff4eb3c
03197178d551434e
20851fda85950116
5a6f51dc9accaf5a
daf5ed94a707ffb9
2854ef15c67fb1ec
465f168d480f6436
a1c5affccef33fdd
0b99ea4719debbfd
c1e7e52aaa546b3f
4c4c91d7f1aba812

RRBLOCK:
0000010000010014
dd541a46885a250a
27db63b2b1c07c04
3137271edc77df52
0a30b7bb909060f6
3b8be702f815cb02
f3186874a331d87f
0263393fa66b6197
52b35fd117f27b73
86ab6924bd948de9
cd5f512d3ca370c5
3bfccfc5238516cc
0ddeacf65b145709
0005d78a44e4ff82
dfc0aa69cee85288
434b48d487ed3911
5118213b7b2efe73
9067c6f6c0e83d59
7d9288b018e73b66
264ee8587d026c60
bd2ff2e3d50a7d49
1b53803c8ff4eb3c
03197178d551434e
20851fda85950116
5a6f51dc9accaf5a
daf5ed94a707ffb9
2854ef15c67fb1ec
465f168d480f6436
a1c5affccef33fdd
0b99ea4719debbfd
c1e7e52aaa546b3f
4c4c91d7f1aba812

The following is an example revocation for a zone:


Zone private key (d, big-endian scalar):
6fea32c05af58bfa
979553d188605fd5
7d8bf9cc263b78d5
f7478c07b998ed70

Zone identifier (ztype|zkey):
000100002ca223e8
79ecc4bbdeb5da17
319281d63b2e3b69
55f1c3775c804a98
d5f8ddaa

Encoded zone identifier (zkl = zTLD):
000G001CM8HYGYFCRJXXXDET2WRS50EP7CQ3PTANY71QEQ409ACDBY6XN8

Difficulty (5 base difficulty + 2 epochs): 7

Signed message:
0000003400000003
0005d66da3598127
000100002ca223e8
79ecc4bbdeb5da17
319281d63b2e3b69
55f1c3775c804a98
d5f8ddaa

Proof:
0005d66da3598127
0000395d1827c000
3ab877d07570f2b8
3ab877d07570f332
3ab877d07570f4f5
3ab877d07570f50f
3ab877d07570f537
3ab877d07570f599
3ab877d07570f5cd
3ab877d07570f5d9
3ab877d07570f66a
3ab877d07570f69b
3ab877d07570f72f
3ab877d07570f7c3
3ab877d07570f843
3ab877d07570f8d8
3ab877d07570f91b
3ab877d07570f93a
3ab877d07570f944
3ab877d07570f98a
3ab877d07570f9a7
3ab877d07570f9b0
3ab877d07570f9df
3ab877d07570fa05
3ab877d07570fa3e
3ab877d07570fa63
3ab877d07570fa84
3ab877d07570fa8f
3ab877d07570fa91
3ab877d07570fad6
3ab877d07570fb0a
3ab877d07570fc0f
3ab877d07570fc43
3ab877d07570fca5
000100002ca223e8
79ecc4bbdeb5da17
319281d63b2e3b69
55f1c3775c804a98
d5f8ddaa053b0259
700039187d1da461
3531502bc4a4eecc
c69900d24f8aac54
30f28fc509270133
1f178e290fe06e82
ce2498ce7b23a340
58e3d6a2f247e92b
c9d7b9ab

Authors' Addresses

Martin Schanzenbach
GNUnet e.V.
Boltzmannstrasse 3
85748 Garching
Germany
Christian Grothoff
Berner Fachhochschule
Hoeheweg 80
CH-2501 Biel/Bienne
Switzerland
Bernd Fix
GNUnet e.V.
Boltzmannstrasse 3
85748 Garching
Germany