Hi Team,
Based on:
https://openssh.com/pq.html
Once connecting to VyOS
- WARNING: connection is not using a post-quantum key exchange algorithm.
- This session may be vulnerable to "store now, decrypt later" attacks.
- The server may need to be upgraded. See https://openssh.com/pq.html
But SSH on VyOS 1.4.4 is capable to handle it:
ssh -Q kex diffie-hellman-group1-sha1 diffie-hellman-group14-sha1 diffie-hellman-group14-sha256 diffie-hellman-group16-sha512 diffie-hellman-group18-sha512 diffie-hellman-group-exchange-sha1 diffie-hellman-group-exchange-sha256 ecdh-sha2-nistp256 ecdh-sha2-nistp384 ecdh-sha2-nistp521 curve25519-sha256 curve25519-sha256@libssh.org sntrup761x25519-sha512 sntrup761x25519-sha512@openssh.com
set service ssh key-exchange Possible completions: <text> Allowed key exchange (KEX) algorithms curve25519-sha256 curve25519-sha256@libssh.org diffie-hellman-group-exchange-sha1 diffie-hellman-group-exchange-sha256 diffie-hellman-group1-sha1 diffie-hellman-group14-sha1 diffie-hellman-group14-sha256 diffie-hellman-group16-sha512 diffie-hellman-group18-sha512 ecdh-sha2-nistp256 ecdh-sha2-nistp384 ecdh-sha2-nistp521
We miss options for:
sntrup761x25519-sha512 sntrup761x25519-sha512@openssh.com
To follow recomendation from OpenSSH:
OpenSSH has offered post-quantum key agreement (KexAlgorithms) by default since release 9.0 (April 2022), initially via the sntrup761x25519-sha512 algorithm. More recently, in OpenSSH 9.9, we have added a second post-quantum key agreement mlkem768x25519-sha256 and it was made the new default scheme in OpenSSH 10.0 (April 2025).
As on VyOS we have
ssh -V OpenSSH_9.2p1 Debian-2+deb12u7, OpenSSL 3.0.17 1 Jul 2025
We can enable:
sntrup761x25519-sha512
sntrup761x25519-sha512@openssh.com
And on newer VyOS enable:
mlkem768x25519-sha256
If we start using OpenSSH 10.0.