LAMPS M. Ounsworth Internet-Draft J. Gray Updates: {"RFC5280"=>nil} (if approved) Entrust Intended status: Standards Track D. Hook Expires: 11 April 2025 KeyFactor M.-J. O. Saarinen Tampere University 8 October 2024 External Keys For Use In Internet X.509 Certificates draft-ounsworth-lamps-pq-external-pubkeys-05 Abstract Many of the post quantum cryptographic algorithms have large public keys. In the interest of reducing bandwidth of transitting X.509 certificates, this document defines new public key and algorithms for referencing external public key data by hash, and location, for example URL. This mechanism is designed to mimic the behaviour of an Authority Information Access extension. About This Document This note is to be removed before publishing as an RFC. The latest revision of this draft can be found at https://EntrustCorporation.github.io/draft-pq-external-pubkeys/draft- ounsworth-pq-external-pubkeys.html. Status information for this document may be found at https://datatracker.ietf.org/doc/draft- ounsworth-lamps-pq-external-pubkeys/. Source for this draft and an issue tracker can be found at https://github.com/EntrustCorporation/draft-pq-external-pubkeys. 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/. Ounsworth, et al. Expires 11 April 2025 [Page 1] Internet-Draft External X.509 Keys October 2024 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 11 April 2025. Copyright Notice Copyright (c) 2024 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/ license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. External Value . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. External Public Key . . . . . . . . . . . . . . . . . . . 3 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 3.1. Module Registration - SMI Security for PKIX Module Identifier . . . . . . . . . . . . . . . . . . . . . . . 4 3.1.1. Object Identifier Registrations - SMI Security for PKIX Algorithms . . . . . . . . . . . . . . . . . . . . . 4 4. Security Considerations . . . . . . . . . . . . . . . . . . . 4 4.1. CSRs and CT logs . . . . . . . . . . . . . . . . . . . . 4 5. Appendices . . . . . . . . . . . . . . . . . . . . . . . . . 5 5.1. ASN.1 Module . . . . . . . . . . . . . . . . . . . . . . 5 5.2. Samples . . . . . . . . . . . . . . . . . . . . . . . . . 6 5.3. Intellectual Property Considerations . . . . . . . . . . 9 6. Contributors and Acknowledgements . . . . . . . . . . . . . . 9 6.1. Making contributions . . . . . . . . . . . . . . . . . . 9 7. Normative References . . . . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 1. Introduction Ounsworth, et al. Expires 11 April 2025 [Page 2] Internet-Draft External X.509 Keys October 2024 2. External Value The id-external-value algorithm identifier is used for identifying a public key or signature which is provided as a reference to external data. id-external-value OBJECT IDENTIFIER ::= { iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) algorithms(6) TBDOID } EDNOTE: for prototyping purposes, id-external-value ::= 1.3.6.1.4.1.22554.4.2 The corresponding subjectPublicKey is the DER encoding of the following structure: ExternalValue ::= SEQUENCE { location GeneralNames, hashAlg AlgorithmIdentifier, hashVal OCTET STRING } Upon retrieval of the referenced data, the hash of the OCTET STRING of the retrieved data (removing base64 encoding as per [RFC4648] if necessary) MUST be verified using hashAlg to match the ExternalPublicKey.hash value. GeneralNames is defined in [RFC5280] as GeneralNames ::= SEQUENCE SIZE (1..MAX) OF GeneralName which we use instead of GeneralName so that certificate issuers can specify multiple backup key servers for high availability or specify key identifiers in multiple formats if the corresponding public keys will be distributed in multiple keystore formats. When multiple key locations are specified, they MUST represent alternative locations for retrieval of the same key and MUST NOT be used as a mechanism to place multiple subject keys into a single certificate. Thus, when multiple key locations are specified, the client MAY try them in any order and stop when it successfully retrieves a public key whose hash matches hashVal. 2.1. External Public Key When used with a public key, algorithm parameters for id-external- value are absent. Ounsworth, et al. Expires 11 April 2025 [Page 3] Internet-Draft External X.509 Keys October 2024 When ExternalValue is placed into a SubjectPublicKeyInfo.subjectPublicKey, the ExternalValue.location MUST refer to a DER-encoded SubjectPublicKeyInfo, which MAY be base64 encoded as per [RFC4648] for easier transport over text protocols. 3. IANA Considerations ## Object Identifier Allocations 3.1. Module Registration - SMI Security for PKIX Module Identifier * Decimal: IANA Assigned - *Replace TBDMOD* * Description: EXTERNAL-PUBKEY-2023 - id-mod-external-pubkey * References: This Document 3.1.1. Object Identifier Registrations - SMI Security for PKIX Algorithms * Attest Statement - Decimal: IANA Assigned - Replace *TBDOID* - Description: id-external-value - References: This Document 4. Security Considerations There are no security implications to externalizing a public key from a certificate as described in this draft. It is of course possible for a malicious actor to replace or tamper with the public key data at the referenced location, but since the hash of the public key data is included in the signed certificate, any such tampering will be detected and the certificate verification will fail. For this reason, external public key data MAY be served over an insecure channel such as HTTP. 4.1. CSRs and CT logs In practice, situations will arise where the ExternalPublicKey.location refers to a location which is not publicly available either because it is in a local keystore, on a private network, or no longer being hosted. Ounsworth, et al. Expires 11 April 2025 [Page 4] Internet-Draft External X.509 Keys October 2024 Not having the public key in a certificate signing request (CSR) could make it substantially harder for CAs to perform vetting of the key, for example for cryptographic strength or checking for prior revocation due to key compromise. A certificate requester MUST make the full public key available to the CA at the time of certificate request either by ensuring that the link in the ExternalPublicKey.location is visible to the CA, or by supplying the full public key to the CA out of band. Not having the public key in Certificate Transparency (CT) logs could make it substantially harder for researchers to perform auditing tasks on CT logs. This may require additional CT mechanisms. 5. Appendices 5.1. ASN.1 Module Ounsworth, et al. Expires 11 April 2025 [Page 5] Internet-Draft External X.509 Keys October 2024 EXTERNAL-PUBKEY-2023 {iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) id-mod(0) id-mod-external-pubkey(TBDMOD)} DEFINITIONS IMPLICIT TAGS ::= BEGIN EXPORTS ALL; IMPORTS GeneralNames FROM PKIX1Implicit-2009 {iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) id-mod(0) id-mod-pkix1-implicit-02(59)} AlgorithmIdentifier{} FROM AlgorithmInformation-2009 {iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) id-mod(0) id-mod-algorithmInformation-02(58)} ; id-external-value OBJECT IDENTIFIER ::= { iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) algorithms(6) TBDOID } ExternalValue ::= SEQUENCE { location GeneralNames, hashAlg AlgorithmIdentifier, hashVal OCTET STRING } END 5.2. Samples Here is a sample of a Kyber1024 end entity certificate with an external public key. A trust anchor certificate using the algorithm ecdsaWithSHA256 is provided so that the Kyber1024 End Entity certificate can be verified. Ounsworth, et al. Expires 11 April 2025 [Page 6] Internet-Draft External X.509 Keys October 2024 This is a modest example demonstrating a 550 byte Kyber1024 certificate and a 2.2 kb external Kyber1024 public key. This "compression" effect will be even more pronounced with algorithms such as Classic McEliece which have public keys in the hundreds of kilobytes; with the external public key mechanism, the size of the certificate remains constant regardless of how large the externalized subject public key is. End entity Kyber1024 Certificate with ExternalValue public key: -----BEGIN CERTIFICATE----- MIIBbDCCARGgAwIBAgIGAYro4QFGMAoGCCqGSM49BAMCMDoxDjAMBgNVBAMMBVFT IENBMRswGQYDVQQKDBJRdWFudGl0eSBTdXJ2ZXlvcnMxCzAJBgNVBAYTAlhYMB4X DTIzMTAwMTAxMzYxNFoXDTI0MDEwOTAxMzYxNFowHTEbMBkGA1UEAwwSRXRoZWwg dGhlIEFhcmR2YXJrMGkwDAYKKwYBBAGBsBoEAgNZADBWMCWGI2ZpbGU6Ly9sb2Nh bF9rZXlzZXJ2ZXIvc3VydmV5b3JzLmRiMAsGCWCGSAFlAwQCAQQg0K1P456WkMCO RxsGOm271ynblXxFCgkTDI78by/RRJCjEDAOMAwGA1UdEwEB/wQCMAAwCgYIKoZI zj0EAwIDSQAwRgIhANqC6ZVDVrgaFFPxJcnhJO6kRGU9dHv5vRDcf2paXxSfAiEA 2s/xoctsB1oCisbjK9HCUw/rzXoVKhkt1ZEXuapJYCk= -----END CERTIFICATE----- For illustrative purposes, the SubjectPublicKeyInfo within the end entity certificate decodes as: subjectPublicKeyInfo SubjectPublicKeyInfo SEQUENCE (2 elem) algorithm AlgorithmIdentifier SEQUENCE (1 elem) algorithm OBJECT IDENTIFIER 1.3.6.1.4.1.22554.4.2 ExternalValue subjectPublicKey BIT STRING (704 bit) SEQUENCE (3 elem) SEQUENCE (1 elem) [6] (35 byte) file://local_keyserver/surveyors.db SEQUENCE (1 elem) OBJECT IDENTIFIER 2.16.840.1.101.3.4.2.1 sha-256 OCTET STRING (32 byte) D0AD4FE39E9690C08E4... The external public key object referenced by the end entity certificate is: Ounsworth, et al. Expires 11 April 2025 [Page 7] Internet-Draft External X.509 Keys October 2024 -----BEGIN PUBLIC KEY----- MIIGNDANBgsrBgEEAYGwGgUGAwOCBiEAPEFAYjZ9CljJTDJiJcKBIVCH6Clk3DDA ybVRPdsXT6An/mAzlVPHjRtginkcrKIlgRq7lhyoyjVmqkqso1wQGON2vZYM8rwU UZFyGUcwykY2bLWJypBvopmUDGumCnARrNqcqRS4zHokOFWZXqcxnVx8DvZsoDc4 LNIEALKh6vFVx1hZ6txEKtxqxrbC1PGsZ4Z1Z9VY3tB/YJkVKmDLqxcrmwFyAHki CEtoaqSxkdB9cBPIlegidjQJS6EqO8aztxu4yWax/jbFu6FOC1cJS2KsBNOjAZvE cMhQIGK0R2a6/tGk6TZBHZtHdlYX6udW5OEnW3Aj49On6cMT2ZMx/vlpsTu0DSoX lvlJjyiWKxalCNQOGcdMLKNaCOk8NmxLsVdck6WtexiRC6WhccaVR0SZoeO4DBBv O7C8mbOrXyyngGmiplNr6oJaY5JbLTMaCsJhiNxvdmLAtxy8EcpRV1FmMkOtqdKX FvCwOwxfRGtxDPlOmAE6AqiZfpdmGAGax5XBbQkK5TDErHIidLbGf3IcQzSBOyFw HPLG+lXGiZRFBFsmioikpjO0K+jKkWJPFNcb0SOYcktgMxGxZeMpQHHDpSeyn7GM uCwVr1BFW8x3S3y+AgMLgEZT3HIPyyljDNwBC1U15sES0zgpV1vB5neQMeBU98AP VpFYJDVDhBJgS4qmJfh1aFuQn3HPT8BQYkzBnve36sKKDhmIAYACyEsMKWJZyhix dkUH4ls4v+o6MrEoLFZZKuNzowNujlq882NeG/a5GCYTN6gp+PVAh5KbHad9Miic +GJKlMPOsJUxzZGEw8iAoBQCZ9dSHdhSDiSPxTsoOso1qyx8dWdJh5AfmQAK7AWi sZh054M67rtaTcpLVbqK8DJiFLsItNhu0JsuUpNNy+RxhUC6TiecgkYWPCtnWMuT /iFghcTLckzO+RrGAedklNEJ7BM8lkq/qLMXqfmu4/aV1OVVpxuyt/YSc1kOPSpS cYTC5gGx85NWpEqmmuUIi/OslEcCeLNl0GgyvFSxncR4eVQ0LDxj1TbOk9t5GVE8 3IDMZxioK5spypm4jKRFqeRKBWKtzCZCm2MciKtEAZUXOSk7qOl8Sig9TeVUg5LP YqmZKCoHeBiKjjlnHxQ5aEM7Dfk8HaWl2IghOXdizPi15XFmrhfLqJijyDQq8xts ibR0yBNXc7BGkjGzTLgAe4UZZncvYFsKjehM1umfpNu1vztnpEt35lWc6UIYezvJ CDBGWdqAJEFJBflwzpgvF2lTIumTTVazePsCAAg38mg1qprFCNcikcmn0PuwUHmS Iza1c9UX/HK4QENt9CyLnKl0vmPEtPWOuvge9Belc9KUibHHBCI24Mg6AbYv2dLO 7ZEBj6krLpUkkEtGTke5zVwRdFMK6+kP4FG9CpVfqNpC7sO0mACkeAMZSiAderS3 MgaiH1RpkGkM11kG/IM6U3vAPMAgO4xHM4fB3Wgf5reBC8ZRR5liYGSDZ9KOHrkw ISZXNaEYLJFBVXd5g/KrsxQ5AWKxqPsMFMW6+Ih3onQ8R5kIkbxM6/U72nmKOAC+ 9bQuCLBqIJo3GFM087B+LmIW5ZJ6FVV9vSIvaDhrBJiHwQSGsssT+2CntGE+aDxh MaVAuLlijgSerBcHkOKhQFAXIKehOENcMfxIW0w4CBCVQrxbUpIiAvpjL0nNUoej GngA+euFD4ZESMzP1UICokOyZRS6VpSQn9ozfDxMxlBPt/M6zwOGt0W9jhacjrIs IyxB3Dm93ysDnaRRmtOWgAAB80ZKNRBp28uWtUbJYzermLmUNQsWK6I5P2y8JogB 3htoryUSduEXYOeAVTCYnmgf3yJswznFPNhGZpNoJ2NnJuKHS7o0OCVRpbuRXMOh TcMNFyc8+8y//Lpu38kDC1fPK6pW9UVhbKRGFAQWpKonWzDGaeihoDQcP1RD8VUv Y2w4MoOpNkdsDgEmoGkv+1EiwLSbThpes1wGa/kx7ihwbAYvuOjFGZIU4Dp+rjJ1 Unk1erFIlayhGOAr5fWaeNOV3QUK9aSPyVV5YRDXZRKJbaJXDla8JLDOCKeO4aV6 JHIT3nFqKNQ= -----END PUBLIC KEY----- For illustrative purposes, the key data, which is itself a SubjectPublicKeyInfo, decodes as: SEQUENCE (2 elem) SEQUENCE (1 elem) OBJECT IDENTIFIER 1.3.6.1.4.1.22554.5.6.3 Kyber1024 BIT STRING (12544 bit) 001111000100000101000 The following trust anchor certificate can be used to validate the above end entity certificate. Ounsworth, et al. Expires 11 April 2025 [Page 8] Internet-Draft External X.509 Keys October 2024 -----BEGIN CERTIFICATE----- MIIBfTCCASSgAwIBAgIGAYro4QBFMAoGCCqGSM49BAMCMDoxDjAMBgNVBAMMBVFT IENBMRswGQYDVQQKDBJRdWFudGl0eSBTdXJ2ZXlvcnMxCzAJBgNVBAYTAlhYMB4X DTIzMTAwMTAxMzYxNFoXDTI0MDEwOTAxMzYxNFowOjEOMAwGA1UEAwwFUVMgQ0Ex GzAZBgNVBAoMElF1YW50aXR5IFN1cnZleW9yczELMAkGA1UEBhMCWFgwWTATBgcq hkjOPQIBBggqhkjOPQMBBwNCAASZNnsQba2aDhAfhCTE670YBBvGfo7cU69VR2I+ NQt321Feh+Au0/S+RobWtyx6JnFnAb/Y00YhQdA1liz0i4lFoxYwFDASBgNVHRMB Af8ECDAGAQH/AgEAMAoGCCqGSM49BAMCA0cAMEQCIHV0TdjJm9vCn3k93xhTXMQ0 D8tQuzXJtFXNGtKk8OQQAiBn8yKLzreor7QrdGUHCH7g0kaDcyI4xXn95aPjgi/V NA== -----END CERTIFICATE----- 5.3. Intellectual Property Considerations None. 6. Contributors and Acknowledgements This document incorporates contributions and comments from a large group of experts. The Editors would especially like to acknowledge the expertise and tireless dedication of the following people, who attended many long meetings and generated millions of bytes of electronic mail and VOIP traffic over the past year in pursuit of this document: Serge Mister (Entrust). We are grateful to all, including any contributors who may have been inadvertently omitted from this list. This document borrows text from similar documents, including those referenced below. Thanks go to the authors of those documents. "Copying always makes things easier and less error prone" - [RFC8411]. 6.1. Making contributions Additional contributions to this draft are welcome. Please see the working copy of this draft at, as well as open issues at: https://github.com/EntrustCorporation/draft-ounsworth-pq-external- keys 7. Normative References [RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006, . Ounsworth, et al. Expires 11 April 2025 [Page 9] Internet-Draft External X.509 Keys October 2024 [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., Housley, R., and W. Polk, "Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008, . [RFC8411] Schaad, J. and R. Andrews, "IANA Registration for the Cryptographic Algorithm Object Identifier Range", RFC 8411, DOI 10.17487/RFC8411, August 2018, . Authors' Addresses Mike Ounsworth Entrust Limited 1000 Innovation Drive Ottawa, Ontario K2K 1E3 Canada Email: mike.ounsworth@entrust.com J. Gray Entrust Email: john.gray@entrust.com D. Hook KeyFactor Email: david.hook@keyfactor.com Markku-Juhani O. Saarinen Tampere University Finland Email: markku-juhani.saarinen@tuni.fi Ounsworth, et al. Expires 11 April 2025 [Page 10]