[COSE] COSE ciphersuite list in draft-ietf-cose-hpke-07

[Rohan Mahy <[e-mail]>]

Hi,

Regarding the list of ciphersuites in draft-ietf-cose-hpke-07:

The MLS working group observed that most people who are interested in using
ChaChaPoly instead of AES are not interested in running NIST Curves either.

I'll also observe that the interest in the CP NIST curves is currently
unproven and that these COSE ciphersuites could be easily added later.

I would like to include the X25519/Kyber768 KEM with AES and ChaChaPoly,
but these could also be included later. There is substantial interest in
using a hybrid KEM to prevent harvest-now/decrypt-later attacks. However, a
desire to publish this spec sooner would be a perfectly reasonable
justification to leave these ciphersuite out.

Concretely, I would propose the following COSE HPKE ciphersuites:

HPKE-Base-P256-SHA256-AES128GCM
HPKE-Base-P384-SHA384-AES256GCM
HPKE-Base-P521-SHA512-AES256GCM
HPKE-Base-X25519-SHA256-AES128GCM
HPKE-Base-X25519-SHA256-ChaCha20Poly1305
HPKE-Base-X448-SHA512-AES256GCM
HPKE-Base-X448-SHA512-ChaCha20Poly1305
HPKE-Base-X25519Kyber768-SHA256-AES256GCM
HPKE-Base-X25519Kyber768-SHA256-ChaCha20Poly1305

Thanks,
-rohan


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