[CFRG] Re: ASN.1 in draft-connolly-cfrg-xwing-kem

[Bas Westerbaan <[e-mail]>]

Hi Russ,

Thanks for this — I'll carve out some time tomorrow to include this. Are
you around tomorrow at the hackathon in case I have some dumb questions?

Best,

 Bas

On Sat, Nov 2, 2024 at 2:52 PM Russ Housley <[e-mail]> wrote:

> Dear Authors:
>
> Please consider including an ASN.1 module in an appendix.  We have seen
> this reduces implementation mistakes, especially by making it clear whether
> IMPLICIT or EXPLICIT TAGS are being employed.  I have provided a suggestion
> for one below.
>
> In addition, I suspect that you do not want the public key wrapped in an
> OCTET STRING when it appears in a certificate.  Hackathon experience with
> Kyber and ML-KEM suggest that it is not needed.  That said, there are times
> that the public key might be used in other contexts.  Sext something like
> this might be appropriate:
>
> ~~~
> No additional encoding of the XWing public key is applied in the
> SubjectPublicKeyInfo field of an X.509 certificate [RFC5280].
>
> No additional encoding of the XWing private key is applied in the
> PrivateKeyInfo field of the privateKey field of the OneAsymmetricKey
> type of an Asymmetric Key Package [RFC5958].
>
> When XWing public key appears outside of aa SubjectPublicKeyInfo type
> in an environment that uses ASN.1 encoding, the XWing public key
> can be encoded as an OCTET STRING by using the XWingPublicKey type.
>
> When the XWing private key appears outside of an Asymmetric Key Package
> in an environment that uses ASN.1 encoding, the XWing private key
> can be encoded as an OCTET STRING by using the XWingPrivateKey type.
> ~~~
>
> If you agree, then yo also need to add:
>
> XWingPrivateKey ::= OCTET STRING to the module below.
>
> Russ
>
>
> = = = = = = = =
>
>
> XWing-KEM-2024
>    { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1)
>      pkcs-9(9) smime(16) modules(0) id-mod-XWing-kem-2024(TBD) }
>
> DEFINITIONS IMPLICIT TAGS ::= BEGIN
>
> -- EXPORTS ALL
>
> IMPORTS
>
>   KEM-ALGORITHM
>     FROM KEMAlgorithmInformation-2023  -- [I-D.housley-lamps-cms-kemri]
>        { iso(1) identified-organization(3) dod(6) internet(1)
>          security(5) mechanisms(5) pkix(7) id-mod(0)
>          id-mod-kemAlgorithmInformation-2023(109) }
>
>   AlgorithmIdentifier{}, PUBLIC-KEY, SMIME-CAPS
>     FROM AlgorithmInformation-2009  -- [RFC5912]
>       { iso(1) identified-organization(3) dod(6) internet(1)
>         security(5) mechanisms(5) pkix(7) id-mod(0)
>         id-mod-algorithmInformation-02(58) } ;
>
>
> -- XWing KEM Algorithm
>
> id-XWing OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
>            dod(6) internet(1) private(4) enterprise(1) 62253 25722 }
>
> XWingPublicKey ::= OCTET STRING
>
> kema-XWing KEM-ALGORITHM ::= {
>    IDENTIFIER id-XWing
>    PARAMS ARE absent
>    PUBLIC-KEYS { pk-XWing }
>    UKM ARE optional
>    SMIME-CAPS { IDENTIFIED BY id-XWing } }
>
> pk-XWing PUBLIC-KEY ::= {
>   IDENTIFIER id-XWing
>   -- KEY no ASN.1 wrapping --
>   PARAMS ARE absent
>   -- PRIVATE-KEY no ASN.1 wrapping --
>   CERT-KEY-USAGE {keyEncipherment} }
>
>
> -- Updates for the KEM-ALGORITHM Set from rfc5990bis
>
> KeyEncapsulationMechanism ::=
>    AlgorithmIdentifier { KEM-ALGORITHM, {KEMAlgorithms} }
>
> KEMAlgorithms KEM-ALGORITHM ::= { kema-XWing, ... }
>
>
> -- Updates for the SMIME-CAPS Set from RFC 5911
>
> SMimeCapsSet SMIME-CAPS ::= {kema-XWing.&smimeCaps, ... }
>
> END
>
>
>