Maik Riechert <[email protected]> wrote:
    > A few weeks ago I've done some experiments on using SSH keys to sign
    > claims using COSE. This was in the context of SCITT which meant that
    > the corresponding public key would also have to be published through a
    > DID, and that worked fine by converting it to JWK.

In most cases, SSH keys are just raw public keys in a particular format.
I'm not sure I understand what value there is in using that specific wrapping.
Often the underlying keys (public and private) are identical, with just
slightly different file wrappings.

    > The main insight of that post is that the first three bytes of SSH
    > protocol signature input are always zero, and since the first three
    > bytes of SSH signatures are always "SSH" it all works out.

    > The same argument can be made for COSE, here for COSE_Sign1:

    > The signature input is the CBOR serialization of the Sig_structure
    > array: ["Signature1", body_protected, sign_protected, aad, payload,
    > [signature]]

    > In hex, the array length is 86, the context string length is 6A, and
    > the context string is 5369676E617475726531. This means the first three
    > bytes are always 86 6A 53, which is different than zero bytes and also
    > different from the SSH signature preamble ("SSH" which is 53 53 34).

    > Is this a sensible analysis? Anything else to watch out for?

I'm not sure what your goals are.
I agree that "SSH signatures" are not COSE signatures, but how does this help
the world?

Seeing that you've CC'ed SCITT, I wonder if you are thinking that using SSH
keys would allow for more natural management for developers?



--
Michael Richardson <[email protected]>, Sandelman Software Works
 -= IPv6 IoT consulting =-



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