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My server has got key_share externsions while TLC 1.3 handshaking:
1 19018 = 0x4a4a = GREASE - OK.
2 25497 = 0x6399 - OpenSSL has not recognized it and written- UNKNOWN...
3 29 - OK

The question is - what extension #2 did I get ?

OpenSSL dump:
extension_type=key_share(51), length=1263
1-NamedGroup: UNKNOWN (19018)
key_exchange: (len=1): 00
2-NamedGroup: UNKNOWN (25497)
key_exchange: (len=1216): 5037ABF5A62426676DFA51365E9575936EA416A71CAEC3DA0...
3 - NamedGroup: ecdh_x25519 (29)
key_exchange: (len=32):
D97B685698D8AEA150DEB26FD7C658B3C1A25FAE9EE9A16B40DA3FE6D0020958

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    $\begingroup$ Please do some minimal research first. A quick search for name group 0x6399 shows that this is X25519Kyber768. $\endgroup$ Commented Apr 30 at 16:55

1 Answer 1

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The question is - what extension #2 did I get ?

This is the proposed Postquantum group X25519Kyber768Draft00 - see https://datatracker.ietf.org/doc/draft-tls-westerbaan-xyber768d00/02/

This is a combination of X25519 along with Kyber 768 (as of the version 3 draft of the Kyber proposal to NIST).

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  • $\begingroup$ Poncho, thank you very much! Probably, my search attempts were unsuccessful $\endgroup$
    – LUN
    Commented Apr 30 at 20:43

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