Parity between OpenSSH and the draft

[csosto-pk]

OpenSSH has implemented [email protected] PQ-hybrid key exchange by default .

The current deviations from our draft are

• It K = K_X25519 || K_NTRU uses . This may change in our draft depending which of the 1, 2a, 2b, 3 option the WG choses.
• It uses method name [email protected]. Our draft may use different ones based on algorithms.
• It uses a different hash function SHA-512.

Long term we would want parity between OpenSSH and our draft.

[csosto-pk]

Replaced [email protected] with [email protected] in the draft.

[csosto-pk]

After checking, using SHA-512 would have negligible performance impact. So keeping SHA-512 in the draft to follow what OpenSSH does for [email protected] for now.

[csosto-pk]

After checking, using option 1 for key derivation does not really affect performance. Also, it does not seem to have any practical security impact on the security of the derived keys. So for now, keeping option 1 to follow what OpenSSH does for [email protected]