Consider a standardized domain separator string

dconnolly / draft-connolly-cfrg-xwing-kem

I-D for a general purpose KEM (key encapsulation mechanism) that includes a hash at the end

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Consider a standardized domain separator string #22

Closed codespree closed 1 month ago

codespree commented 1 month ago

I know the X-Wing ASCII art label is very cute (I like it too!)

But the composite KEM drafts use the hex of DER encoding of the OID as the dom-sep: https://github.com/codespree/quantcrypt/blob/cef13f4c40b6da1bf2f2633e6e2bf28bca29994a/src/asn1/asn_util.rs#L25

Perhaps, in the interest of compatibility, this might be a good approach?

https://www.ietf.org/archive/id/draft-ietf-lamps-pq-composite-kem-05.html#name-domain-separators

For you to decide upon.

bwesterb commented 1 month ago

It’s not good for performance: it would overflow the blocksize and thus add another keccak call. Also we can’t change xwing now that we have assigned codepoints.

codespree commented 1 month ago

Ok.

codespree commented 1 month ago

By the way, I updated my lib based on your last commit and comments: https://github.com/codespree/quantcrypt/commit/ab05443b8964f72729e12ab1da466ca95cdc0a75 and moved to Shake256 and updated the vectors in tests.

bwesterb commented 1 month ago

Great!Met een vriendelijke groet, BasOn 25 Oct 2024, at 23:48, Varun Chatterji @.> wrote: By the way, I updated my lib based on your last commit and comments: @. and moved to Shake256 and updated the vectors in tests.

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