| Internet-Draft | DRIP DKI | May 2023 |
| Moskowitz & Card | Expires 19 November 2023 | [Page] |
The DRIP Entity Tag (DET) public Key Infrastructure (DKI) is a specific variant of classic Public Key Infrastructures (PKI) where the orginization is around the DET, in place of X.520 Distinguished Names. Further, the DKI uses DRIP Endorsements in place of X.509 certificates for establishing trust within the DKI.¶
There is a shadow PKI behind the DKI, with many of its X.509 fields mirroring content in the DRIP Endorsements. This PKI can at times be used where X.509 is expected and non-constrained communication links are available that can handle their larger size.¶
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A DRIP Entity Tag (DET, [RFC9374]) public Key Infrastructure (DKI) is a strict hierarchy, governed by the administrator of the DET prefix [IPv6-SPECIAL] and having the authority to authorize RAAs. RAAs in turn authorize HDAs within their domain. This authorization is managed via a set of DETs whose sole use is to define the DKI. The RAA Authorization DETs MUST reside in HID = RAA#|0 (Apex Authorization DET in HID = 0|0).¶
There are three main classifications/types of DETs:¶
All DETs exist in DET-Endorsements (Appendix B of [drip-registries]). These DET-Endorsements provide the proof of registration and thus trust. These DETs, through chained Endorsements define the DKI as follows:¶
+----------+
| Auth |
+-o------o-+
| |
| +-o-----+
Apex | +--o----+|
| |Endorse|+
| +---o---+
| |
| +-o-----+
| +--o----+|
| |CRL,Srv|+
| +-------+
|
******************|************************************
+-o--------+
+-o--------+|
| Auth |+
+--o-----o-+
| |
| +-o-----+
RAAs | +--o----+|
| |Endorse|+
| +---o---+
| |
| +-o-----+
| +--o----+|
| |CRL,Srv|+
| +-------+
|
******************|************************************
+-o--------+
+-o--------+|
| Auth |+
+----o-----+
|
+-o-----+
HDAs +--o----+|
|Endorse|+
+---o---+
|
+-o-----+
+--o----+|
|CRL,Srv||
|UAS |+
+-------+
*******************************************************
The Authorization DETs exist in a set of DET-Authorization-Endorsements. The lifetime of these endorsements SHOULD be no less than 1 year, recommended 5 years, and should not exceed 10 years. Endorsements SHOULD be reissued prior to expiry (may be for a new DET). DETs used to define this authorization are replaced per undetermined policy (note these DETs do very little signing, see section...).¶
This separation of DET type roles reduce the risk of private key loss for the critical Authentication DETs by making them infrequently used. It does make the chain of trust for a HDA customers' Operational DETs to be 4 Endorsements.¶
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.¶
This document uses the terms defined in Section 2.2 of [RFC9153] and in Section 2 of [drip-architecture]. The following new terms are used in the document:¶
The Apex Authorization DET is used to endorse RAA Authorization DETs and its own Apex Endorsing DETs; it has no other use. This is the case for all Authorization DETs. Apex Endorsing DETs are used to endorse DETs, with HID= 0|0, used by Apex services.¶
Each RAA use its Authorization DET (HID = RAA#|0) to endorse its RAA Endorsing DET(s) (also HID = RAA#|0) and for endorsing its HDA Authorization DETs (HID = RAA#|HDA#).¶
An RAA may have multiple Endorsing DETs (HID = RAA#|0), each for a different use (e.g. CRL signing, RAA server signing). It is expected that, over time, an RAA will rollover its Endorsing DETs, thus at times there will be more than ONE Endorsing DET per role in use.¶
Each HDA use its Authorization DET to endorse its HDA Endorsing DETs (e.g. RAA=267, HDA=567).¶
An HDA Endorsing DET is used to endorse Operational DETs; those used by the HDA for its services (e.g. USS) and for Devices (e.g. UA, GCS, ground infrastructure) partaking in the HDA's services.¶
The primary view of the DKI is within DNS. There are two main DNS structures, one for DETs and one for DKI entities.¶
In the DET DNS structure, only the Apex and RAA levels MUST be DNSSEC signed. The HDA level may be too dynamic for DNSSEC signing (e.g. hundreds of new EE Operational DETs per hour); trust in the EE Operational DETs within the HDA level comes through inclusion of the HDA Endorsement of EE object. A slow-churn HDA MAY use DNSSEC. The RAA and HDA levels MUST contain their Endorsement by higher object; this provides the needed trust in the Endorsement of EE objects. The Apex level Endorsement is self-signed, thus trust in it is only possible via DNSSEC. Other RR within these levels will vary. There may be HIP, TLSA, URI RR.¶
Each level needs FQDNs for its Authorization DET and Endorsing DET(s) (e.g. PTR to DETs?). FQDNs for services offered may also be present, or a URI for the commercial FQDN for the DKI Entity. TLSA RR of DET SPKI may be directly included here. Same with HIP RR. The Authorization Endorsement SHOULD be present, as SHOULD be Endorsing Endorsements.¶
The Offline cache of HDA Endorsements, used to verify various EE signed objects without needing DNS access, SHOULD consist of the HDA Authentication DET Endorsements of the HDA Endorsement DETs. Thus the receiver has a trusted source of the HDA Endorsement DET Public Key (HI) in a DRIP standard object (136 bytes). If the DKI DNS tree includes GEO location data and coverage, a receiver could query some service for a trusted cache within some radius of its location. Such as, please tell me of all HDAs within 100KM of...¶
This cache MAY contain the full chain up to the Apex. This could be helpful in limited connectivity environments when encountering an Endorsing HDA DET under a know Authenticated HDA or RAA. The needed trust chain could be shorter.¶
The RAA range of 16376 - 16383 are reserved for testing. It test DET DNS structure under drip-testing.org will use these. RAAs 16376 - 16389 are preallocated in this test DNS with 16390 - 16383 available for testing setting up RAAs. Within RAAs 16376 - 16383, HDAs 16376 - 16383 will be preset for testing of Operational DETs. Other HDAs within RAAs 16376 - 16383 additional HDAs can be made available for testing of HDA setup and running said HDAs.¶
It is anticipated that once a production DNS is established, these test RAAs and HDAs will carry forward. The migration could be as simple as the production Apex Endorsing the test RAA Authorization DETs and moving the various test DNS structures to the production structure.¶
TBD¶
In development is an X.509 PKI to shadow the DKI. The X.509 certificates are minimalistic (less than 400 bytes for DER). Any DRIP specific OIDs should come from the ICAO arc (e.g. 1.3.27.16.2). Important X.509 fields like issuerKeyIdentifier will have DETs rather than public key hashes, so software will need to specifically handle them.¶
Distiguished Names will follow DET hierarchy and not map well into traditional PKI usage.¶
This is a work in progress.¶
TBD¶
Needs description of risk to Authorization DET private keys for broad trees (e.g. lots of RAAs).¶
TBD¶