| Internet-Draft | IKEv2 PQTH Auth | August 2024 |
| Jun & Morioka | Expires 28 February 2025 | [Page] |
One IPsec area that would be impacted by Cryptographically Relevant Quantum Computer (CRQC) is IKEv2 authentication based on classic asymmetric cryptograph algorithms: e.g RSA, ECDSA; which are widely deployed authentication options of IKEv2. There are new Post-Quantum Cryptograph (PQC) algorithms for digital signature like NIST [ML-DSA], however it takes time for new cryptograph algorithms to mature, so there is security risk to use only the new algorithm before it is field proven. This document describes a IKEv2 hybrid authentication scheme that could contain both classic and PQC algorithms, so that authentication is secure as long as one algorithm in the hybrid scheme is secure.¶
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A Cryptographically Relevant Quantum Computer (CRQC) could break classic asymmetric cryptograph algorithms: e.g RSA, ECDSA; which are widely deployed authentication options of IKEv2. New Post-Quantum Cryptograph (PQC) algorithms for digital signature are being standardized at the time of writing like NIST [ML-DSA], however consider potential flaws in the new algorithm's specifications and implementations, it will take time for these new PQC algorithms to be field proven. So it is risky to only use PQC algorithms before they are mature. There is more detailed discussion on motivation of a hybrid approach for authentication in Section 1.3 of [I-D.ietf-pquip-hybrid-signature-spectrums].¶
This document describes a IKEv2 hybrid authentication scheme that contains both classic and PQC algorithms, so that authentication is secure as long as one algorithm in the hybrid scheme is secure.¶
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.¶
Cryptographically Relevant Quantum Computer (CRQC): A quantum computer that is capable of breaking real world cryptographic systems.¶
Post-Quantum Cryptograph (PQC) algorithms: Asymmetric cryptograph algorithms are thought to be secure against CRQC.¶
Traditional Cryptograph algorithms: Existing asymmetric cryptograph algorithms could be broken by CRQC, like RSA, ECDSA ..etc.¶
There is no changes introduced in this document to the IKEv2 key exchange process, although it MUST be also resilient to CRQC when using along with the PQ/T hybrid authentication, for example key exchange using the PPK as defined in [RFC8784], or hybrid key exchanges that include PQC algorithm via multiple key exchange process as defined in [RFC9370].¶
The hybrid authentication exchanges is illustrated in an example depicted in Figure 1, the key exchange uses PPK, however it could be other key exchanges that involves PQC algorithm since how key exchange is done is transparent to authentication.¶
Initiator Responder
-------------------------------------------------------------------
HDR, SAi1, KEi, Ni,
N(SIGNATURE_HASH_ALGORITHMS), N(USE_PPK) -->
<-- HDR, SAr1, KEr, Nr, [CERTREQ,] N(USE_PPK),
N(SIGNATURE_HASH_ALGORITHMS),
N(SUPPORTED_AUTH_METHODS)
HDR, SK {IDi, CERT+, [CERTREQ,]
[IDr,] AUTH, SAi2,
TSi, TSr, N(PPK_IDENTITY, PPK_ID),
N(SUPPORTED_AUTH_METHODS)} -->
<-- HDR, SK {IDr, CERT+, [CERTREQ,]
AUTH, [N(PPK_IDENTITY)]}
Both peers includes SIGNATURE_HASH_ALGORITHMS as defined in Section 4 of [RFC7427] notification in IKE_SA_INIT exchange to indicate supported hash algorithms used with digital signature.¶
Responder includes SUPPORTED_AUTH_METHODS as defined in [RFC9593] notification include a list of supported authentication methods announcements includes a hybrid authentication announcements with following format:¶
1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length (>3) | Auth Method | Cert Link 1 | Alg 1 Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ AlgorithmIdentifier 1 ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cert Link 2 | Alg 2 Len | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
~ AlgorithmIdentifier 2 ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ ... ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cert Link N | Alg N Len | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
~ AlgorithmIdentifier N ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The announcement include a list algorithms could be used for hybrid signature¶
Auth Method: A new value to be allocated by IANA¶
Cert Link N: Links corresponding signature algorithm N with a particular CA. as defined in Section 3.2.2 of [RFC9593]¶
AlgorithmIdentifier N: The variable-length ASN.1 object that is encoded using Distinguished Encoding Rules (DER) [X.690] and identifies the signature algorithm;¶
Receiver of this announcement could choose one PQC algorithm and one traditional algorithm from the list to create the hybrid signature.¶
Initiator also includes SUPPORTED_AUTH_METHODS notification in IKE_AUTH request message to announce its support of hybrid authentication.¶
The IKEv2 AUTH payload has following format as defined in Section 3.8 of [RFC7296]:¶
1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Payload |C| RESERVED | Payload Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Auth Method | RESERVED |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Authentication Data ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
For hybrid authentication, the AUTH Method has value defined in Section 4.1¶
The Authentication Data field follows format defined in Section 3 of [RFC7427]:¶
1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ASN.1 Length | AlgorithmIdentifier ASN.1 object |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ AlgorithmIdentifier ASN.1 object continuing ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Signature Value ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Signature Value is created via following procedure:¶
Choose a hash algorithm H from peer's SIGNATURE_HASH_ALGORITHMS, a PQC algorithm Sig1 and a traditional algorithm Sig2 from peer's hybrid authentication method announcement;¶
Follow the procedure defined in Section 4.2 of [I-D.ietf-lamps-pq-composite-sigs], where the domain separator is the value in Section 7.1 of [I-D.ietf-lamps-pq-composite-sigs] correspond to the combination of Sig1, Sig2 and H.¶
The domain separator is also used as AlgorithmIdentifier in the Authentication Data.¶
The corresponding certificates of Sig1 and Sig2 MUST be put in the first and second CERT payload, in the order, of the message;¶
So far, this document assumes the signing certificate contains a key of single algorithm, however there might be certificate with composite key as define in [I-D.ietf-lamps-pq-composite-sigs], in such case, AUTH payload is created with same procedure in Section 4.2:¶
Sig1 and Sig2 are specified by the signing certificate¶
Supported composite signature algorithms are announced via SUPPORTED_AUTH_METHODS notification with 3-Octet announcement as defined in Section 3.2.2 of [RFC9593].¶
The security of general PQ/T hybrid authentication is discussed in [I-D.ietf-pquip-hybrid-signature-spectrums].¶
This document uses mechanisms defined in [RFC7427] and [RFC9593], the security discussion in the corresponding RFCs also apply.¶
This document requests a value in "IKEv2 Authentication Method" subregistry under IANA "Internet Key Exchange Version 2 (IKEv2) Parameters" registry¶
TODO acknowledge.¶