The Entity Attestation Token (EAT)Qualcomm Technologies Inc.5775 Morehouse DriveSan DiegoCaliforniaUSA+1 858 651 7200mandyam@qti.qualcomm.comSecurity Theory LLClgl@island-resort.comQualcomm Technologies Inc.5775 Morehouse DriveSan DiegoCaliforniaUSA+1 858 651 4299mballest@qti.qualcomm.comQualcomm Technologies Inc.279 Farnborough RoadFarnboroughGU14 7LSUnited Kingdom+44 1252 363189jodonogh@qti.qualcomm.com
Internet
RATS Working Groupsigning attestation cborAn Entity Attestation Token (EAT) provides a signed (attested) set of
claims that describe state and characteristics of an entity, typically
a device like a phone or an IoT device. These claims are used by a
relying party to determine how much it wishes to trust the entity.An EAT is either a CWT or JWT with some attestation-oriented
claims. To a large degree, all this document does is extend
CWT and JWT.TBDRemote device attestation is a fundamental service that allows a remote
device such as a mobile phone, an Internet-of-Things (IoT) device, or
other endpoint to prove itself to a relying party, a server or a
service. This allows the relying party to know some characteristics
about the device and decide whether it trusts the device.Remote attestation is a fundamental service that can underlie other
protocols and services that need to know about the trustworthiness of
the device before proceeding. One good example is biometric
authentication where the biometric matching is done on the device. The
relying party needs to know that the device is one that is known to do
biometric matching correctly. Another example is content protection
where the relying party wants to know the device will protect the
data. This generalizes on to corporate enterprises that might want to
know that a device is trustworthy before allowing corporate data to be
accessed by it.The notion of attestation here is large and may include, but is not
limited to the following:Proof of the make and model of the device hardware (HW)Proof of the make and model of the device processor, particularly
for security-oriented chipsMeasurement of the software (SW) running on the deviceConfiguration and state of the deviceEnvironmental characteristics of the device such as its GPS locationTODO: mention use for Attestation Evidence and Results.For flexibility and ease of imlpementation in a wide variety of environments, EATs can be either CBOR or JSON format.
This specification simultaneously describes both formats.An EAT is either a CWT as defined in , a UCCS as defined in , or a JWT as defined in .
This specification extends those specifications with additional claims for attestation.The identification of a protocol element as an EAT, whether CBOR or JSON format, follows the general conventions used by CWT, JWT and UCCS.
Largely this depends on the protocol carrying the EAT.
In some cases it may be by content type (e.g., MIME type).
In other cases it may be through use of CBOR tags.
There is no fixed mechanism across all use cases.This specification uses CDDL, , as the primary formalism to
define each claim. The implementor then interprets the CDDL to come
to either the CBOR or JSON
representation. In the case of JSON, Appendix E of is
followed. Additional rules are given in of this
document where Appendix E is insufficient. (Note that this is not to
define a general means to translate between CBOR and JSON, but only to
define enough such that the claims defined in this document can be
rendered unambiguously in JSON).The CWT specification was authored before CDDL was available and did not use it.
This specification includes a CDDL definition of most of what is described in .An “entity” can be any device or device subassembly (“submodule”) that
can generate its own attestation in the form of an EAT. The
attestation should be cryptographically verifiable by the EAT
consumer. An EAT at the device-level can be composed of several
submodule EAT’s. It is assumed that any entity that can create an EAT
does so by means of a dedicated root-of-trust (RoT).Modern devices such as a mobile phone have many different execution
environments operating with different security levels. For example, it
is common for a mobile phone to have an “apps” environment that runs
an operating system (OS) that hosts a plethora of downloadable
apps. It may also have a TEE (Trusted Execution Environment) that is
distinct, isolated, and hosts security-oriented functionality like
biometric authentication. Additionally, it may have an eSE (embedded
Secure Element) - a high security chip with defenses against HW
attacks that can serve as a RoT. This device attestation format
allows the attested data to be tagged at a security level from which
it originates. In general, any discrete execution environment that
has an identifiable security level can be considered an entity.TODO: Rewrite (or eliminate) this section in light of the RATS architecture draft.At least the following three participants exist in all EAT operating
models. Some operating models have additional participants.
This is the phone, the IoT device, the sensor, the sub-assembly or
such that the attestation provides information about.
The company that made the entity. This may be a chip vendor, a
circuit board module vendor or a vendor of finished consumer products.
The server, service or company that makes use of the information in
the EAT about the entity.In all operating models, the manufacturer provisions some secret
attestation key material (AKM) into the entity during manufacturing.
This might be during the manufacturer of a chip at a fabrication
facility (fab) or during final assembly of a consumer product or any
time in between. This attestation key material is used for signing
EATs.In all operating models, hardware and/or software on the entity create
an EAT of the format described in this document. The EAT is always
signed by the attestation key material provisioned by the
manufacturer.In all operating models, the relying party must end up knowing that
the signature on the EAT is valid and consistent with data from claims
in the EAT. This can happen in many different ways. Here are some
examples.The EAT is transmitted to the relying party. The relying party gets
corresponding key material (e.g. a root certificate) from the
manufacturer. The relying party performs the verification.The EAT is transmitted to the relying party. The relying party
transmits the EAT to a verification service offered by the
manufacturer. The server returns the validated claims.The EAT is transmitted directly to a verification service, perhaps
operated by the manufacturer or perhaps by another party. It
verifies the EAT and makes the validated claims available to the
relying party. It may even modify the claims in some way and re-sign
the EAT (with a different signing key).All these operating models are supported and there is no preference
of one over the other. It is important to support this variety of
operating models to generally facilitate deployment and to allow for
some special scenarios. One special scenario has a validation service
that is monetized, most likely by the manufacturer. In another, a
privacy proxy service processes the EAT before it is transmitted to
the relying party. In yet another, symmetric key material is used for
signing. In this case the manufacturer should perform the
verification, because any release of the key material would enable a
participant other than the entity to create valid signed EATs.The following is not standardized for EAT, just the same they are not
standardized for CWT or JWT.EATs may be transmitted by any protocol the same as CWTs and JWTs. For
example, they might be added in extension fields of other protocols,
bundled into an HTTP header, or just transmitted as files. This
flexibility is intentional to allow broader adoption. This flexibility
is possible because EAT’s are self-secured with signing (and possibly
additionally with encryption and anti-replay). The transmission
protocol is not required to fulfill any additional security
requirements.For certain devices, a direct connection may not exist between the
EAT-producing device and the Relying Party. In such cases, the EAT
should be protected against malicious access. The use of COSE and JOSE
allows for signing and encryption of the EAT. Therefore, even if the
EAT is conveyed through intermediaries between the device and Relying
Party, such intermediaries cannot easily modify the EAT payload or
alter the signature.The term “signing scheme” is used to refer to the system that includes
end-end process of establishing signing attestation key material in
the entity, signing the EAT, and verifying it. This might involve key
IDs and X.509 certificate chains or something similar but
different. The term “signing algorithm” refers just to the algorithm
ID in the COSE signing structure. No particular signing algorithm or
signing scheme is required by this standard.There are three main implementation issues driving this. First, secure
non-volatile storage space in the entity for the attestation key
material may be highly limited, perhaps to only a few hundred bits, on
some small IoT chips. Second, the factory cost of provisioning key
material in each chip or device may be high, with even millisecond
delays adding to the cost of a chip. Third, privacy-preserving signing
schemes like ECDAA (Elliptic Curve Direct Anonymous Attestation) are
complex and not suitable for all use cases.Over time to faciliate interoperability, some signing schemes may be
defined in EAT profiles or other documents either in the IETF or outside.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 when, and only when, they appear in all
capitals, as shown here.This document reuses terminology from JWT , COSE
, and CWT .
The human-readable name used to identify a claim.
The CBOR map key or JSON name used to identify a claim.
The value portion of the claim. A claim value can be any CBOR data item or JSON value.
The CBOR map or JSON object that contains the claims conveyed by the CWT or JWT.
The key material used to sign the EAT token. If it is done
symmetrically with HMAC, then this is a simple symmetric key.
If it is done with ECC, such as an IEEE DevID , then this
is the private part of the EC key pair. If ECDAA
is used, (e.g., as used by Enhanced Privacy ID, i.e. EPID) then it is the key material
needed for ECDAA.This section describes new claims defined for attestation. It also
mentions several claims defined by CWT and JWT that are particularly
important for EAT.Note also:
* Any claim defined for CWT or JWT may be used in an EAT including
those in the CWT and JWT IANA
claims registries.All claims are optionalNo claims are mandatoryAll claims that are not understood by implementations MUST be ignoredThere are no default values or meanings assigned to absent claims
other than they are not reported. The reason for a claim’s absence may
be the implementation not supporting the claim, an inability to
determine its value, or a preference to report in a different way such
as a proprietary claim.CDDL along with text descriptions is used to define each claim
indepdent of encoding. Each claim is defined as a CDDL group (the
group is a general aggregation and type definition feature of
CDDL). In the encoding section , the CDDL groups turn into
CBOR map entries and JSON name/value pairs.TODO: add paragraph here about use for Attestation Evidence and for Results.CWT defines the “cti” claim. JWT defines the “jti” claim. These are
equivalent to each other in EAT and carry a unique token identifier as
they do in JWT and CWT. They may be used to defend against re use of
the token but are distinct from the nonce that is used by the relying
party to guarantee freshness and defend against replay.The “iat” claim defined in CWT and JWT is used to indicate the
date-of-creation of the token, the time at which the claims are
collected and the token is composed and signed.The data for some claims may be held or cached for some period of
time before the token is created. This period may be long, even
days. Examples are measurements taken at boot or a geographic
position fix taken the last time a satellite signal was received.
There are individual timestamps associated with these claims to
indicate their age is older than the “iat” timestamp.CWT allows the use floating-point for this claim. EAT disallows
the use of floating-point. No token may contain an iat claim in
float-point format. Any recipient of a token with a floating-point
format iat claim may consider it an error. A 64-bit integer
representation of epoch time can represent a range of +/- 500 billion
years, so the only point of a floating-point timestamp is to
have precession greater than one second. This is not needed for EAT.All EATs should have a nonce to prevent replay attacks. The nonce is
generated by the relying party, the end consumer of the token. It is
conveyed to the entity over whatever transport is in use before the
token is generated and then included in the token as the nonce claim.This documents the nonce claim for registration in the IANA CWT
claims registry. This is equivalent to the JWT nonce claim that is
already registered.The nonce must be at least 8 bytes (64 bits) as fewer are unlikely
to be secure. A maximum of 64 bytes is set to limit the memory
a constrained implementation uses. This size range is not set
for the already-registered JWT nonce, but it should follow
this size recommendation when used in an EAT.Multiple nonces are allowed to accommodate multistage verification
and consumption.UEID’s identify individual manufactured entities / devices such as a
mobile phone, a water meter, a Bluetooth speaker or a networked
security camera. It may identify the entire device or a submodule or
subsystem. It does not identify types, models or classes of
devices. It is akin to a serial number, though it does not have to be
sequential.UEID’s must be universally and globally unique across manufacturers
and countries. UEIDs must also be unique across protocols and systems,
as tokens are intended to be embedded in many different protocols and
systems. No two products anywhere, even in completely different
industries made by two different manufacturers in two different
countries should have the same UEID (if they are not global and
universal in this way, then relying parties receiving them will have
to track other characteristics of the device to keep devices distinct
between manufacturers).There are privacy considerations for UEID’s. See .The UEID should be permanent. It should never change for a given
device / entity. In addition, it should not be reprogrammable. UEID’s
are variable length. All implementations MUST be able to receive
UEID’s that are 33 bytes long (1 type byte and 256 bits). The
recommended maximum sent is also 33 bytes.When the entity constructs the UEID, the first byte is a type and the
following bytes the ID for that type. Several types are allowed to
accommodate different industries and different manufacturing processes
and to give options to avoid paying fees for certain types of
manufacturer registrations.Creation of new types requires a Standards Action .Type ByteType NameSpecification0x01RANDThis is a 128, 192 or 256 bit random number generated once and stored in the device. This may be constructed by concatenating enough identifiers to make up an equivalent number of random bits and then feeding the concatenation through a cryptographic hash function. It may also be a cryptographic quality random number generated once at the beginning of the life of the device and stored. It may not be smaller than 128 bits.0x02IEEE EUIThis makes use of the IEEE company identification registry. An EUI is either an EUI-48, EUI-60 or EUI-64 and made up of an OUI, OUI-36 or a CID, different registered company identifiers, and some unique per-device identifier. EUIs are often the same as or similar to MAC addresses. This type includes MAC-48, an obsolete name for EUI-48. (Note that while devices with multiple network interfaces may have multiple MAC addresses, there is only one UEID for a device) , 0x03IMEIThis is a 14-digit identifier consisting of an 8-digit Type Allocation Code and a 6-digit serial number allocated by the manufacturer, which SHALL be encoded as byte string of length 14 with each byte as the digit’s value (not the ASCII encoding of the digit; the digit 3 encodes as 0x03, not 0x33). The IMEI value encoded SHALL NOT include Luhn checksum or SVN information. UEID’s are not designed for direct use by humans (e.g., printing on
the case of a device), so no textual representation is defined.The consumer (the relying party) of a UEID MUST treat a UEID as a
completely opaque string of bytes and not make any use of its internal
structure. For example, they should not use the OUI part of a type
0x02 UEID to identify the manufacturer of the device. Instead they
should use the oemid claim that is defined elsewhere. The reasons for
this are:UEIDs types may vary freely from one manufacturer to the next.New types of UEIDs may be created. For example, a type 0x07 UEID may
be created based on some other manufacturer registration scheme.Device manufacturers are allowed to change from one type of UEID to
another anytime they want. For example, they may find they can
optimize their manufacturing by switching from type 0x01 to type
0x02 or vice versa. The main requirement on the manufacturer is
that UEIDs be universally unique.TODO: this claim is likely to be dropped in favor of Endorsement identifier and locators.This claim describes the parts of the device or entity that are
creating the EAT. Often it will be tied back to the device or chip
manufacturer. The following table gives some examples:NameDescriptionAcme-TEEThe EATs are generated in the TEE authored and configured by “Acme”Acme-TPMThe EATs are generated in a TPM manufactured by “Acme”Acme-Linux-KernelThe EATs are generated in a Linux kernel configured and shipped by “Acme”Acme-TAThe EATs are generated in a Trusted Application (TA) authored by “Acme”TODO: consider a more structure approach where the name and the URI
and other are in separate fields.TODO: This needs refinement. It is somewhat parallel to issuer claim
in CWT in that it describes the authority that created the token.The IEEE operates a global registry for MAC addresses and company IDs.
This claim uses that database to identify OEMs. The contents of the
claim may be either an IEEE MA-L, MA-M, MA-S or an IEEE CID
. An MA-L, formerly known as an OUI, is a 24-bit value
used as the first half of a MAC address. MA-M similarly is a 28-bit
value uses as the first part of a MAC address, and MA-S, formerly
known as OUI-36, a 36-bit value. Many companies already have purchased
one of these. A CID is also a 24-bit value from the same space as an
MA-L, but not for use as a MAC address. IEEE has published Guidelines
for Use of EUI, OUI, and CID and provides a lookup
services Companies that have more than one of these IDs or MAC address blocks
should pick one and prefer that for all their devices.Commonly, these are expressed in Hexadecimal Representation
also called the Canonical format. When this claim is
encoded the order of bytes in the bstr are the same as the order in the
Hexadecimal Representation. For example, an MA-L like “AC-DE-48” would
be encoded in 3 bytes with values 0xAC, 0xDE, 0x48. For JSON encoded
tokens, this is further base64url encoded.The hardware version can be claimed at three different levels, the chip, the circuit board and the final device assembly.
An EAT can include any combination these claims.The hardware version is a simple text string the format of which is set by each manufacturer.
The structure and sorting order of this text string can be specified using the version-scheme item from CoSWID .The hardware version can also be given by a 13-digit European Article Number .
An EAN-13 is also known as an International Article Number or most commonly as a bar code.
This claim is the ASCII text representation of actual digits often printed with a bar code.
Use of this claim must comply with the EAN allocation and assignment rules.
For example, this requires the manufacturer to obtain a manufacture code from GS1.Both the simple version string and EAN-13 versions may be included for the same hardware.TODO: Add claims that reference CoSWID.This claim characterizes the device/entity
ability to defend against attacks aimed at capturing the signing
key, forging claims and at forging EATs. This is done by
defining four security levels as described below. This is similar
to the key protection types defined by the Fast Identity Online (FIDO) Alliance .These claims describe security environment and countermeasures
available on the end-entity / client device where the attestation key
reside and the claims originate.
There is some expectation that implementor will
protect the attestation signing keys at this level. Otherwise
the EAT provides no meaningful security assurances.
Entities at this level should not be general-purpose
operating environments that host features such as app download
systems, web browsers and complex productivity applications.
It is akin to the Secure Restricted level (see below) without the
security orientation. Examples include a Wi-Fi subsystem,
an IoT camera, or sensor device.
Entities at this level must meet the criteria defined by FIDO Allowed
Restricted Operating Environments . Examples include TEE’s and
schemes using virtualization-based security. Like the FIDO security goal,
security at this level is aimed at defending well against large-scale
network / remote attacks against the device.
Entities at this level must include substantial defense
against physical or electrical attacks against the device itself.
It is assumed any potential attacker has captured the device and can
disassemble it. Example include TPMs and Secure Elements.The entity should claim the highest security level it achieves and no higher.
This set is not extensible so as to provide a common interoperable description of security level to the relying party.
If a particular implementation considers this claim to be inadequate, it can define its own proprietary claim.
It may consider including both this claim as a coarse indication of security and its own proprietary claim as a refined indication.This claim is not intended as a replacement for a proper end-device
security certification schemes such as those based on FIPS 140
or those based on Common Criteria . The
claim made here is solely a self-claim made by the Entity Originator.The value of true indicates secure boot is enabled. Secure boot is
considered enabled when base software, the firmware and operating
system, are under control of the entity manufacturer identified in the
oemid claimd described in . This may because the software is
in ROM or because it is cryptographically authenticated or some
combination of the two or other.This applies to system-wide or submodule-wide debug facilities of the
target device / submodule like JTAG and diagnostic hardware built into
chips. It applies to any software debug facilities related to root,
operating system or privileged software that allow system-wide memory
inspection, tracing or modification of non-system software like user
mode applications.This characterization assumes that debug facilities can be enabled and
disabled in a dynamic way or be disabled in some permanent way such
that no enabling is possible. An example of dynamic enabling is one
where some authentication is required to enable debugging. An example
of permanent disabling is blowing a hardware fuse in a chip. The specific
type of the mechanism is not taken into account. For example, it does
not matter if authentication is by a global password or by per-device
public keys.As with all claims, the absence of the debug level claim means
it is not reported. A conservative interpretation might assume
the Not Disabled state. It could however be that it is reported
in a proprietary claim.This claim is not extensible so as to provide a common interoperable description of debug status to the relying party.
If a particular implementation considers this claim to be inadequate, it can define its own proprietary claim.
It may consider including both this claim as a coarse indication of debug status and its own proprietary claim as a refined indication.The higher levels of debug disabling requires that all debug disabling
of the levels below it be in effect. Since the lowest level requires
that all of the target’s debug be currently disabled, all other levels
require that too.There is no inheritance of claims from a submodule to a superior
module or vice versa. There is no assumption, requirement or guarantee
that the target of a superior module encompasses the targets of
submodules. Thus, every submodule must explicitly describe its own
debug state. The verifier or relying party receiving an EAT cannot
assume that debug is turned off in a submodule because there is a claim
indicating it is turned off in a superior module.An individual target device / submodule may have multiple debug
facilities. The use of plural in the description of the states
refers to that, not to any aggregation or inheritance.The architecture of some chips or devices may be such that a debug
facility operates for the whole chip or device. If the EAT for such
a chip includes submodules, then each submodule should independently
report the status of the whole-chip or whole-device debug facility.
This is the only way the relying party can know the debug status
of the submodules since there is no inheritance.If any debug facility, even manufacturer hardware diagnostics, is
currently enabled, then this level must be indicated.This level indicates all debug facilities are currently disabled. It
may be possible to enable them in the future, and it may also be
possible that they were enabled in the past after the
target device/sub-system booted/started, but they are currently disabled.This level indicates all debug facilities are currently disabled and
have been so since the target device/sub-system booted/started.This level indicates all non-manufacturer facilities are permanently
disabled such that no end user or developer cannot enable them. Only
the manufacturer indicated in the OEMID claim can enable them. This
also indicates that all debug facilities are currently disabled and
have been so since boot/start.This level indicates that all debug capabilities for the target
device/sub-module are permanently disabled.An EAT may include a cryptographic key such as a public key.
The signing of the EAT binds the key to all the other claims in the token.The purpose for inclusion of the key may vary by use case.
For example, the key may be included as part of an IoT device onboarding protocol.
When the FIDO protocol includes a pubic key in its attestation message, the key represents the binding of a user, device and relying party.
This document describes how claims containing keys should be defined for the various use cases.
It does not define specific claims for specific use cases.Keys in CBOR format tokens SHOULD be the COSE_Key format and keys in JSON format tokens SHOULD be the JSON Web Key format .
These two formats support many common key types.
Their use avoids the need to decode other serialization formats.
These two formats can be extended to support further key types through their IANA registries.The general confirmation claim format , may also be used.
It provides key encryption.
It also allows for inclusion by reference through a key ID.
The confirmation claim format may employed in the definition of some new claim for a a particular use case.When the actual confirmation claim is included in an EAT, this document associates no use case semantics other than proof of posession.
Different EAT use cases may choose to associate further semantics.
The key in the confirmation claim MUST be protected the same as the key used to sign the EAT.
That is, the same, equivalent or better hardware defenses, access controls, key generation and such must be used.The location claim gives the location of the device entity from which the attestation originates.
It is derived from the W3C Geolocation API .
The latitude, longitude, altitude and accuracy must conform to .
The altitude is in meters above the ellipsoid.
The two accuracy values are positive numbers in meters.
The heading is in degrees relative to true north.
If the device is stationary, the heading is NaN (floating-point not-a-number).
The speed is the horizontal component of the device velocity in meters per second.When encoding floating-point numbers half-precision should not be used.
It usually does not provide enough precision for a geographic location.
It is not a requirement that the receiver of an EAT implement half-precision, so the receiver may not be able to decode the location.The location may have been cached for a period of time before token
creation. For example, it might have been minutes or hours or more
since the last contact with a GPS satellite. Either the timestamp or
age data item can be used to quantify the cached period. The timestamp
data item is preferred as it a non-relative time.The age data item can be used when the entity doesn’t know what time
it is either because it doesn’t have a clock or it isn’t set. The
entity must still have a “ticker” that can measure a time
interval. The age is the interval between acquisition of the location
data and token creation.See location-related privacy considerations in below.The “uptime” claim contains a value that represents the number of
seconds that have elapsed since the entity or submod was last booted.The Boot Seed claim is a random value created at system boot time that will allow differentiation of reports from different boot sessions.
This value is usually public and not protected.
It is not the same as a seed for a random number generator which must be kept secret.EAT’s may be used in the context of several different applications. The intended-use
claim provides an indication to an EAT consumer about the intended usage
of the token. This claim can be used as a way for an application using EAT to internally distinguish between different ways it uses EAT.
Generic attestation describes an application where the EAT consumer
requres the most up-to-date security assessment of the attesting entity. It
is expected that this is the most commonly-used application of EAT.
Entities that are registering for a new service may be expected to
provide an attestation as part of the registration process. This intended-use
setting indicates that the attestation is not intended for any use but registration.
Entities may be provisioned with different values or settings by an EAT
consumer. Examples include key material or device management trees. The consumer
may require an EAT to assess device security state of the entity prior to provisioning.
Certifying authorities (CA’s) may require attestations prior to
the issuance of certificates related to keypairs hosted at the entity. An
EAT may be used as part of the certificate signing request (CSR).
An EAT consumer may require an attestation as part of an accompanying
proof-of-possession (PoP) appication. More precisely, a PoP transaction is intended
to provide to the recipient cryptographically-verifiable proof that the sender has posession
of a key. This kind of attestation may be neceesary to verify the
security state of the entity storing the private key used in a PoP application.The profile claim is a text string that simply gives the name of the profile to which the token purports to adhere to.
It may name an IETF document, some other document or no particular document.
There is no requirement that the named document be publicly accessible.See for a detailed description of a profile.Note that this named “eat-profile” for JWT and is distinct from the already registered “profile” claim in the JWT claims registry.Some devices are complex, having many subsystems or submodules. A
mobile phone is a good example. It may have several connectivity
submodules for communications (e.g., Wi-Fi and cellular). It may have
subsystems for low-power audio and video playback. It may have one or
more security-oriented subsystems like a TEE or a Secure Element.The claims for each these can be grouped together in a submodule.The submods part of a token are in a single map/object with many entries, one
per submodule. There is only one submods map in a token. It is
identified by its specific label. It is a peer to other claims, but it
is not called a claim because it is a container for a claim set rather
than an individual claim. This submods part of a token allows what
might be called recursion. It allows claim sets inside of claim sets
inside of claims sets…Each entry in the submod map is one of two types:A non-token submodule that is a map or object directly containing claims for the submodule.A nested EAT that is a fully formed, independently signed EAT tokenThis is simply a map or object containing claims about the submodule.It may contain claims that are the same as its surrounding token or superior submodules.
For example, the top-level of the token may have a UEID, a submod may have a different UEID and a further subordinate submodule may also have a UEID.It is signed/encrypted along with the rest of the token and thus the claims are secured by the same Attester with the same signing key as the rest of the token.If a token is in CBOR format (a CWT or a UCCS), all non-token submodules must be CBOR format.
If a token in in JSON format (a JWT), all non-token submodules must be in JSON format.When decoding, this type of submodule is recognized from the other type by being a data item of type map for CBOR or type object for JSON.This type of submodule is a fully formed secured EAT as defined in this document except that it MUST NOT be a UCCS or an unsecured JWT.
A nested token that is one that is always secured using COSE or JOSE, usually by an independent Attester.
When the surrounding EAT is a CWT or secured JWT, the nested token becomes securely bound with the other claims in the surrounding token.It is allowed to have a CWT as a submodule in a JWT and vice versa, but this SHOULD be avoided unless necessary.They type of an EAT nested in a CWT is determined by whether the CBOR type is a text string or a byte string.
If a text string, then it is a JWT.
If a byte string, then it is a CWT.A CWT nested in a CBOR-format token is always wrapped by a byte string for easier handling with standard CBOR decoders and token processing APIs that will typically take a byte buffer as input.Nested CWTs may be either a CWT CBOR tag or a CWT Protocol Message.
COSE layers in nested CWT EATs MUST be a COSE_Tagged_Message, never a COSE_Untagged_Message.
If a nested EAT has more than one level of COSE, for example one that is both encrypted and signed, a COSE_Tagged_message must be used at every level.When a CWT is nested in a JWT, it must be as a 55799 tag in order to distinguish it from a nested JWT.When a nested EAT in a JWT is decoded, first remove the base64url encoding.
Next, check to see if it starts with the bytes 0xd9d9f7.
If so, then it is a CWT as a JWT will never start with these four bytes.
If not if it is a JWT.Other than the 55799 tag requirement, tag usage for CWT’s nested in a JSON format token follow the same rules as for CWTs nested in CBOR-format tokens.
It may be a CWT CBOR tag or a CWT Protocol Message and COSE_Tagged_Message MUST be used at all COSE layers.To incorporate a UCCS token as a submodule, it MUST be as a non-token submodule.
This can be accomplished inserting the content of the UCCS Tag into the submodule map.
The content of a UCCS tag is exactly a map of claims as required for a non-token submodule.
If the UCCS is not a UCCS tag, then it can just be inserted into the submodule map directly.The definition of a nested EAT type of submodule is that it is one that is secured (signed) by an Attester.
Since UCCS tokens are unsecured, they do not fulfill this definition and must be non-token submodules.To incorporate an Unsecured JWT as a submodule, the null-security JOSE wrapping should be removed.
The resulting claims set should be inserted as a non-token submodule.To incorporate a UCCS token in a surrounding JSON token, the UCCS token claims should be translated from CBOR to JSON.
To incorporate an Unsecured JWT into a surrounding CBOR-format token, the null-security JOSE should be removed and the claims translated from JSON to CBOR.The subordinate modules do not inherit anything from the containing
token. The subordinate modules must explicitly include all of their
claims. This is the case even for claims like the nonce and age.This rule is in place for simplicity. It avoids complex inheritance
rules that might vary from one type of claim to another.The security level of the non-token subordinate modules should always
be less than or equal to that of the containing modules in the case of non-token
submodules. It makes no sense for a module of lesser security to be
signing claims of a module of higher security. An example of this is a
TEE signing claims made by the non-TEE parts (e.g. the high-level OS)
of the device.The opposite may be true for the nested tokens. They usually have
their own more secure key material. An example of this is an embedded
secure element.The label or name for each submodule in the submods map is a text
string naming the submodule. No submodules may have the same name.TODO: fill this section in. It will discuss key IDs, endorsement ID and such that
are needed as input needed to by the Verifier to verify the signature. This will
NOT discuss the contents of an Endorsement, just and ID/locator.This EAT specification does not gaurantee that implementations of it will interoperate.
The variability in this specification is necessary to accommodate the widely varying use cases.
An EAT profile narrows the specification for a specific use case.
An ideal EAT profile will gauarantee interoperability.The profile can be named in the token using the profile claim described in .The following is a list of EAT, CWT, UCCS, JWS, COSE, JOSE and CBOR options that a profile should address.The profile should indicate whether the token format should be CBOR, JSON, both or even some other encoding.
If some other encoding, a specification for how the CDDL described here is serialized in that encoding is necessary.This should be addressed for the top-level token and for any nested tokens.
For example, a profile might require all nested tokens to be of the same encoding of the top level token.The profile should indicate whether definite-length arrays/maps, indefinite-length arrays/maps or both are allowed.
A good default is to allow only definite-length arrays/maps.An alternate is to allow both definite and indefinite-length arrays/maps.
The decoder should accept either.
Encoders that need to fit on very small hardware or be actually implement in hardware can use indefinite-length encoding.This applies to individual EAT claims, CWT and COSE parts of the implementation.The profile should indicate whether definite-length strings, indefinite-length strings or both are allowed.
A good default is to allow only definite-length strings.
As with map and array encoding, allowing indefinite-length strings can be beneficial for some smaller implementations.COSE and JOSE have several options for signed, MACed and encrypted messages.
EAT/CWT has the option to have no protection using UCCS and JOSE has a NULL protection option.
It is possible to implement no protection, sign only, MAC only, sign then encrypt and so on.
All combinations allowed by COSE, JOSE, JWT, CWT and UCCS are allowed by EAT.The profile should list the protections that must be supported by all decoders implementing the profile.
The encoders them must implement a subset of what is listed for the decoders, perhaps only one.Implementations may choose to sign or MAC before encryption so that the implementation layer doing the signing or MACing can be the smallest.
It is often easier to make smaller implementations more secure, perhaps even implementing in solely in hardware.
The key material for a signature or MAC is a private key, while for encryption it is likely to be a public key.
The key for encryption requires less protection.The profile document should list the COSE algorithms that a Verifier must implement.
The Attester will select one of them.
Since there is no negotiation, the Verifier should implement all algorithms listed in the profile.Section describes a number of methods for identifying a verification key.
The profile document should specify one of these or one that is not described.
The ones described in this document are only roughly described.
The profile document should go into the full detail.Similar to, or perhaps the same as Verification Key Identification, the profile may wish to specify how Endorsements are to be identified.
However note that Endorsement Identification is optional, where as key identification is not.The profile can list claims whose absence results in Verification failure.The profile can list claims whose presence results in Verification failure.The profile may describe entirely new claims.
These claims can be required or optional.The profile may lock down optional aspects of individual claims.
For example, it may require altitude in the location claim, or it may require that HW Versions always be described using EAN-13.The profile should specify whether the token should be a CWT Tag or not.
Similarly, the profile should specify whether the token should be a UCCS tag or not.When COSE protection is used, the profile should specify whether COSE tags are used or not.
Note that RFC 8392 requires COSE tags be used in a CWT tag.Often a tag is unncessary because the surrounding or carrying protocol identifies the object as an EAT.This makes use of the types defined in CDDL Appendix D, Standard Prelude.Some of the CDDL included here is for claims that are defined in CWT or JWT or are in the IANA CWT or JWT registries.
CDDL was not in use when these claims where defined.time-int is identical to the epoch-based time, but disallows
floating-point representation.This section provides CDDL for the claims defined in CWT. It is
non-normative as is the authoritative definition of these
claims.JSON should be encoded per RFC 8610 Appendix E. In addition, the
following CDDL types are encoded in JSON as follows:bstr – must be base64url encodedtime – must be encoded as NumericDate as described section 2 of .string-or-uri – must be encoded as StringOrURI as described section 2 of .CBOR allows data items to be serialized in more than one form.
If the sender uses a form that the receiver can’t decode, there will not be interoperability.This specification gives no blanket requirements to narrow CBOR serialization for all uses of EAT.
This allows individual uses to tailor serialization to the environment.
It also may result in EAT implementations that don’t interoperate.One way to guarantee interoperability is to clearly specify CBOR serialization in a profile document.
See for a list of serialization issues that should be addressed.EAT will be commonly used where the device generating the attestation is constrained and the receiver/verifier of the attestation is a capacious server.
Following is a set of serialization requirements that work well for that use case and are guaranteed to interoperate.
Use of this serialization is recommended where possible, but not required.
An EAT profile may just reference the following section rather than spell out serialization details.Preferred serialization described in section 4.1 of is not required.
The EAT decoder must accept all forms of number serialization.
The EAT encoder may use any form it wishes.The EAT decoder must accept indefinite length arrays and maps as described in section 3.2.2 of .
The EAT encoder may use indefinite length arrays and maps if it wishes.The EAT decoder must accept indefinite length strings as described in section 3.2.3 of .
The EAT encoder may use indefinite length strings if it wishes.Sorting of maps by key is not required.
The EAT decoder must not rely on sorting.Deterministic encoding described in Section 4.2 of is not required.Basic validity described in section 5.3.1 of must be followed.
The EAT encoder must not send duplicate map keys/labels or invalid UTF-8 strings.Claims defined for EAT are compatible with those of CWT
so the CWT Claims Registry is re used. No new IANA registry
is created. All EAT claims should be registered in the
CWT and JWT Claims Registries.The following is design guidance for creating new EAT claims, particularly those to be registered with IANA.Much of this guidance is generic and could also be considered when designing new CWT or JWT claims.It is a broad goal that EATs can be processed by relying parties in a general way regardless of the type, manufacturer or technology of the device from which they originate.
It is a goal that there be general-purpose verification implementations that can verify tokens for large numbers of use cases with special cases and configurations for different device types.
This is a goal of interoperability of the semantics of claims themselves, not just of the signing, encoding and serialization formats.This is a lofty goal and difficult to achieve broadly requiring careful definition of claims in a technology neutral way.
Sometimes it will be difficult to design a claim that can represent the semantics of data from very different device types.
However, the goal remains even when difficult.Claims should be defined such that they are not specific to an operating system.
They should be applicable to multiple large high-level operating systems from different vendors.
They should also be applicable to multiple small embedded operating systems from multiple vendors and everything in between.Claims should not be defined such that they are specific to a SW environment or programming language.Claims should not be defined such that they are specific to a chip or particular hardware.
For example, they should not just be the contents of some HW status register as it is unlikely that the same HW status register with the same bits exists on a chip of a different manufacturer.The boot and debug state claims in this document are an example of a claim that has been defined in this neutral way.Many use cases will have EATs generated by some of the most secure hardware and software that exists.
Secure Elements and smart cards are examples of this.
However, EAT is intended for use in low-security use cases the same as high-security use case.
For example, an app on a mobile device may generate EATs on its own.Claims should be defined and registered on the basis of whether they are useful and interoperable, not based on security level.
In particular, there should be no exclusion of claims because they are just used only in low-security environments.Where possible, claims should use already standardized data items, identifiers and formats.
This takes advantage of the expertise put into creating those formats and improves interoperability.Often extant claims will not be defined in an encoding or serialization format used by EAT.
It is preferred to define a CBOR and JSON format for them so that EAT implementations do not require a plethora of encoders and decoders for serialization formats.In some cases, it may be better to use the encoding and serialization as is.
For example, signed X.509 certificates and CRLs can be carried as-is in a byte string.
This retains interoperability with the extensive infrastructure for creating and processing X.509 certificates and CRLs.EAT allows the definition and use of proprietary claims.For example, a device manufacturer may generate a token with proprietary claims intended only for verification by a service offered by that device manufacturer.
This is a supported use case.In many cases proprietary claims will be the easiest and most obvious way to proceed, however for better interoperability, use of general standardized claims is preferred.Claim Name: UEIDClaim Description: The Universal Entity IDJWT Claim Name: N/AClaim Key: 8Claim Value Type(s): byte stringChange Controller: IESGSpecification Document(s): this documentTODO: add the rest of the claims in hereCertain EAT claims can be used to track the owner of an entity and
therefore, implementations should consider providing privacy-preserving
options dependent on the intended usage of the EAT. Examples would
include suppression of location claims for EAT’s provided to
unauthenticated consumers.A UEID is usually not privacy-preserving. Any set of relying parties
that receives tokens that happen to be from a single device will be
able to know the tokens are all from the same device and be able to
track the device. Thus, in many usage situations ueid violates
governmental privacy regulation. In other usage situations UEID will
not be allowed for certain products like browsers that give privacy
for the end user. It will often be the case that tokens will not have
a UEID for these reasons.There are several strategies that can be used to still be able to put
UEID’s in tokens:The device obtains explicit permission from the user of the device
to use the UEID. This may be through a prompt. It may also be through
a license agreement. For example, agreements for some online banking
and brokerage services might already cover use of a UEID.The UEID is used only in a particular context or particular use
case. It is used only by one relying party.The device authenticates the relying party and generates a derived
UEID just for that particular relying party. For example, the relying
party could prove their identity cryptographically to the device, then
the device generates a UEID just for that relying party by hashing a
proofed relying party ID with the main device UEID.Note that some of these privacy preservation strategies result in multiple UEIDs
per device. Each UEID is used in a different context, use case or system
on the device. However, from the view of the relying party, there is just
one UEID and it is still globally universal across manufacturers.Geographic location is most always considered personally identifiable information.
Implementers should consider laws and regulations governing the transmission of location data from end user devices to servers and services.
Implementers should consider using location management facilities offered by the operating system on the device generating the attestation.
For example, many mobile phones prompt the user for permission when before sending location data.The security considerations provided in Section 8 of and Section 11
of apply to EAT in its CWT and JWT form, respectively. In addition,
implementors should consider the following.Private key material can be used to sign and/or encrypt the EAT, or
can be used to derive the keys used for signing and/or encryption. In
some instances, the manufacturer of the entity may create the key
material separately and provision the key material in the entity
itself. The manfuacturer of any entity that is capable of producing
an EAT should take care to ensure that any private key material be
suitably protected prior to provisioning the key material in the
entity itself. This can require creation of key material in an
enclave (see for definition of “enclave”), secure
transmission of the key material from the enclave to the entity using
an appropriate protocol, and persistence of the private key material
in some form of secure storage to which (preferably) only the entity
has access.Regarding transmission of key material from the enclave to the entity,
the key material may pass through one or more intermediaries.
Therefore some form of protection (“key wrapping”) may be necessary.
The transmission itself may be performed electronically, but can also
be done by human courier. In the latter case, there should be minimal
to no exposure of the key material to the human (e.g. encrypted
portable memory). Moreover, the human should transport the key
material directly from the secure enclave where it was created to a
destination secure enclave where it can be provisioned.As stated in Section 8 of , “The security of the CWT relies
upon on the protections offered by COSE”. Similar considerations
apply to EAT when sent as a CWT. However, EAT introduces the concept
of a nonce to protect against replay. Since an EAT may be created by
an entity that may not support the same type of transport security as
the consumer of the EAT, intermediaries may be required to bridge
communications between the entity and consumer. As a result, it is
RECOMMENDED that both the consumer create a nonce, and the entity
leverage the nonce along with COSE mechanisms for encryption and/or
signing to create the EAT.Similar considerations apply to the use of EAT as a JWT. Although the
security of a JWT leverages the JSON Web Encryption (JWE) and JSON Web
Signature (JWS) specifications, it is still recommended to make use of
the EAT nonce.In many cases, more than one EAT consumer may be required to fully
verify the entity attestation. Examples include individual consumers
for nested EATs, or consumers for individual claims with an EAT. When
multiple consumers are required for verification of an EAT, it is
important to minimize information exposure to each consumer. In
addition, the communication between multiple consumers should be
secure.For instance, consider the example of an encrypted and signed EAT with
multiple claims. A consumer may receive the EAT (denoted as the
“receiving consumer”), decrypt its payload, verify its signature, but
then pass specific subsets of claims to other consumers for evaluation
(“downstream consumers”). Since any COSE encryption will be removed
by the receiving consumer, the communication of claim subsets to any
downstream consumer should leverage a secure protocol (e.g.one that
uses transport-layer security, i.e. TLS),However, assume the EAT of the previous example is hierarchical and
each claim subset for a downstream consumer is created in the form of
a nested EAT. Then transport security between the receiving and
downstream consumers is not strictly required. Nevertheless,
downstream consumers of a nested EAT should provide a nonce unique to
the EAT they are consuming.Key words for use in RFCs to Indicate Requirement LevelsIn many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.Concise Binary Object Representation (CBOR)The Concise Binary Object Representation (CBOR) is a data format whose design goals include the possibility of extremely small code size, fairly small message size, and extensibility without the need for version negotiation. These design goals make it different from earlier binary serializations such as ASN.1 and MessagePack.This document obsoletes RFC 7049, providing editorial improvements, new details, and errata fixes while keeping full compatibility with the interchange format of RFC 7049. It does not create a new version of the format.JSON Web Key (JWK)A JSON Web Key (JWK) is a JavaScript Object Notation (JSON) data structure that represents a cryptographic key. This specification also defines a JWK Set JSON data structure that represents a set of JWKs. Cryptographic algorithms and identifiers for use with this specification are described in the separate JSON Web Algorithms (JWA) specification and IANA registries established by that specification.JSON Web Token (JWT)JSON Web Token (JWT) is a compact, URL-safe means of representing claims to be transferred between two parties. The claims in a JWT are encoded as a JSON object that is used as the payload of a JSON Web Signature (JWS) structure or as the plaintext of a JSON Web Encryption (JWE) structure, enabling the claims to be digitally signed or integrity protected with a Message Authentication Code (MAC) and/or encrypted.Proof-of-Possession Key Semantics for JSON Web Tokens (JWTs)This specification describes how to declare in a JSON Web Token (JWT) that the presenter of the JWT possesses a particular proof-of- possession key and how the recipient can cryptographically confirm proof of possession of the key by the presenter. Being able to prove possession of a key is also sometimes described as the presenter being a holder-of-key.Guidelines for Writing an IANA Considerations Section in RFCsMany protocols make use of points of extensibility that use constants to identify various protocol parameters. To ensure that the values in these fields do not have conflicting uses and to promote interoperability, their allocations are often coordinated by a central record keeper. For IETF protocols, that role is filled by the Internet Assigned Numbers Authority (IANA).To make assignments in a given registry prudently, guidance describing the conditions under which new values should be assigned, as well as when and how modifications to existing values can be made, is needed. This document defines a framework for the documentation of these guidelines by specification authors, in order to assure that the provided guidance for the IANA Considerations is clear and addresses the various issues that are likely in the operation of a registry.This is the third edition of this document; it obsoletes RFC 5226.Ambiguity of Uppercase vs Lowercase in RFC 2119 Key WordsRFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings.CBOR Object Signing and Encryption (COSE)Concise Binary Object Representation (CBOR) is a data format designed for small code size and small message size. There is a need for the ability to have basic security services defined for this data format. This document defines the CBOR Object Signing and Encryption (COSE) protocol. This specification describes how to create and process signatures, message authentication codes, and encryption using CBOR for serialization. This specification additionally describes how to represent cryptographic keys using CBOR.CBOR Web Token (CWT)CBOR Web Token (CWT) is a compact means of representing claims to be transferred between two parties. The claims in a CWT are encoded in the Concise Binary Object Representation (CBOR), and CBOR Object Signing and Encryption (COSE) is used for added application-layer security protection. A claim is a piece of information asserted about a subject and is represented as a name/value pair consisting of a claim name and a claim value. CWT is derived from JSON Web Token (JWT) but uses CBOR rather than JSON.Concise Data Definition Language (CDDL): A Notational Convention to Express Concise Binary Object Representation (CBOR) and JSON Data StructuresThis document proposes a notational convention to express Concise Binary Object Representation (CBOR) data structures (RFC 7049). Its main goal is to provide an easy and unambiguous way to express structures for protocol messages and data formats that use CBOR or JSON.Proof-of-Possession Key Semantics for CBOR Web Tokens (CWTs)This specification describes how to declare in a CBOR Web Token (CWT) (which is defined by RFC 8392) that the presenter of the CWT possesses a particular proof-of-possession key. Being able to prove possession of a key is also sometimes described as being the holder-of-key. This specification provides equivalent functionality to "Proof-of-Possession Key Semantics for JSON Web Tokens (JWTs)" (RFC 7800) but using Concise Binary Object Representation (CBOR) and CWTs rather than JavaScript Object Notation (JSON) and JSON Web Tokens (JWTs).National Imagery and Mapping Agency Technical Report 8350.2, Third EditionNational Imagery and Mapping AgencyCBOR Web Token (CWT) ClaimsIANAJSON Web Token (JWT) ClaimsIANAA CBOR Tag for Unprotected CWT Claims Sets3rd Generation Partnership Project; Technical Specification Group Core Network and Terminals; Numbering, addressing and identification3GPPFIDO Authenticator Allowed Restricted Operating Environments ListThe FIDO AllianceInternational Article Number - EAN/UPC barcodesGS1Concise Software Identification TagsA Universally Unique IDentifier (UUID) URN NamespaceThis specification defines a Uniform Resource Name namespace for UUIDs (Universally Unique IDentifier), also known as GUIDs (Globally Unique IDentifier). A UUID is 128 bits long, and can guarantee uniqueness across space and time. UUIDs were originally used in the Apollo Network Computing System and later in the Open Software Foundation\'s (OSF) Distributed Computing Environment (DCE), and then in Microsoft Windows platforms.This specification is derived from the DCE specification with the kind permission of the OSF (now known as The Open Group). Information from earlier versions of the DCE specification have been incorporated into this document. [STANDARDS-TRACK]Internet Security Glossary, Version 2This Glossary provides definitions, abbreviations, and explanations of terminology for information system security. The 334 pages of entries offer recommendations to improve the comprehensibility of written material that is generated in the Internet Standards Process (RFC 2026). The recommendations follow the principles that such writing should (a) use the same term or definition whenever the same concept is mentioned; (b) use terms in their plainest, dictionary sense; (c) use terms that are already well-established in open publications; and (d) avoid terms that either favor a particular vendor or favor a particular technology or mechanism over other, competing techniques that already exist or could be developed. This memo provides information for the Internet community.Birthday attackIEEE Standard, "IEEE 802.1AR Secure Device Identifier"Ecma International, "ECMAScript Language Specification, 5.1 Edition", ECMA Standard 262Geolocation API Specification 2nd EditionWorldwide Web ConsortiumGuidelines for Use of Extended Unique Identifier (EUI), Organizationally Unique Identifier (OUI), and Company ID (CID)IEEE Registration Authority AssignmentsIEEE Registration AuthorityIEEE Standard For Local And Metropolitan Area Networks Overview And ArchitectureFIDO Registry of Predefined ValuesThe FIDO AllianceSecurity Requirements for Cryptographic ModulesNational Institue of StandardsCommon Criteria for Information Technology Security EvaluationThis is shown in CBOR diagnostic form. Only the payload signed by COSE
is shown.This calculation is to determine the probability of a collision of
UEIDs given the total possible entity population and the number of
entities in a particular entity management database.Three different sized databases are considered. The number of devices
per person roughly models non-personal devices such as traffic lights,
devices in stores they shop in, facilities they work in and so on,
even considering individual light bulbs. A device may have
individually attested subsystems, for example parts of a car or a
mobile phone. It is assumed that the largest database will have at
most 10% of the world’s population of devices. Note that databases
that handle more than a trillion records exist today.The trillion-record database size models an easy-to-imagine reality
over the next decades. The quadrillion-record database is roughly at
the limit of what is imaginable and should probably be accommodated.
The 100 quadrillion datadbase is highly speculative perhaps involving
nanorobots for every person, livestock animal and domesticated
bird. It is included to round out the analysis.Note that the items counted here certainly do not have IP address and
are not individually connected to the network. They may be connected
to internal buses, via serial links, Bluetooth and so on. This is
not the same problem as sizing IP addresses.PeopleDevices / PersonSubsystems / DeviceDatabase PortionDatabase Size10 billion1001010%trillion (10^12)10 billion100,0001010%quadrillion (10^15)100 billion1,000,0001010%100 quadrillion (10^17)This is conceptually similar to the Birthday Problem where m is the
number of possible birthdays, always 365, and k is the number of
people. It is also conceptually similar to the Birthday Attack where
collisions of the output of hash functions are considered.The proper formula for the collision calculation isHowever, for the very large values involved here, this formula requires floating
point precision higher than commonly available in calculators and SW so this
simple approximation is used. See .For this calculation:Database Size128-bit UEID192-bit UEID256-bit UEIDtrillion (10^12)2 * 10^-158 * 10^-355 * 10^-55quadrillion (10^15)2 * 10^-098 * 10^-295 * 10^-49100 quadrillion (10^17)2 * 10^-058 * 10^-255 * 10^-45Next, to calculate the probability of a collision occurring in one year’s
operation of a database, it is assumed that the database size is in
a steady state and that 10% of the database changes per year. For example,
a trillion record database would have 100 billion states per year. Each
of those states has the above calculated probability of a collision.This assumption is a worst-case since it assumes that each
state of the database is completely independent from the previous state.
In reality this is unlikely as state changes will be the addition or
deletion of a few records.The following tables gives the time interval until there is a probability of
a collision based on there being one tenth the number of states per year
as the number of records in the database.Database Size128-bit UEID192-bit UEID256-bit UEIDtrillion (10^12)60,000 years10^24 years10^44 yearsquadrillion (10^15)8 seconds10^14 years10^34 years100 quadrillion (10^17)8 microseconds10^11 years10^31 yearsClearly, 128 bits is enough for the near future thus the requirement that UEIDs
be a minimum of 128 bits.There is no requirement for 256 bits today as quadrillion-record databases
are not expected in the near future and because this time-to-collision
calculation is a very worst case. A future update of the standard may
increase the requirement to 256 bits, so there is a requirement that
implementations be able to receive 256-bit UEIDs.A UEID is not a UUID by conscious choice for the following
reasons.UUIDs are limited to 128 bits which may not be enough for some future
use cases.Today, cryptographic-quality random numbers are available from common
CPUs and hardware. This hardware was introduced between 2010 and 2015.
Operating systems and cryptographic libraries give access to this
hardware. Consequently, there is little need for implementations
to construct such random values from multiple sources on their own.Version 4 UUIDs do allow for use of such cryptographic-quality
random numbers, but do so by mapping into the overall UUID
structure of time and clock values. This structure is of no
value here yet adds complexity. It also slightly reduces the
number of actual bits with entropy.UUIDs seem to have been designed for scenarios where the implementor
does not have full control over the environment and uniqueness has to
be constructed from identifiers at hand. UEID takes the view that
hardware, software and/or manufacturing process directly implement
UEID in a simple and direct way. It takes the view that cryptographic
quality random number generators are readily available as they are
implemented in commonly used CPU hardware.The following is a list of known changes from the previous drafts. This list is
non-authoritative. It is meant to help reviewers see the significant
differences.Added UEID design rationale appendixThis is a fairly large change in the orientation of the document, but
no new claims have been added.Separate information and data model using CDDL.Say an EAT is a CWT or JWTUse a map to structure the boot_state and location claimsClarifications and corrections for OEMID claimMinor spelling and other fixesAdd the nonce claim, clarify jti claimRoll all EUIs back into one UEID typeUEIDs can be one of three lengths, 128, 192 and 256.Added appendix justifying UEID design and size.Submods part now includes nested eat tokens so they can be named and
there can be more tha one of themLots of fixes to the CDDLAdded security considerationsSplit boot_state into secure-boot and debug-disable claimsDebug disable is an enumerated type rather than BooleansChange IMEI-based UEIDs to be encoded as a 14-byte stringCDDL cleaned up some moreCDDL allows for JWTs and UCCSsCWT format submodules are byte string wrappedAllows for JWT nested in CWT and vice versaAllows UCCS (unsigned CWTs) and JWT unsecured tokensClarify tag usage when nesting tokensAdd section on key inclusionAdd hardware version claimsCollected CDDL is now filled in. Other CDDL corrections.Rename debug-disable to debug-status; clarify that it is not extensibleSecurity level claim is not extensibleImprove specification of location claim and added a location privacy sectionAdd intended use claimCDDL format issues resolvedCorrected reference to Location Privacy sectionAdded boot-seed claimRework CBOR interoperability sectionAdded profiles claim and section