OpenSSH 9.0: scp over SFTP and hybrid key exchange

Since the release of April 8, 2022, scp transfers data over the SFTP protocol instead of the historical one it inherited from rcp. The difference shows wherever a setup relied on the remote shell – wildcards such as * are expanded by the client itself, but variables or command substitution are not, so scp host:'$HOME/x.conf' . may no longer behave as before. For scripts that is a reason to verify transfers after an upgrade rather than assume them.

The second change is in key exchange: the default became the hybrid sntrup761x25519, a classical curve combined with a post-quantum part. The motivation is “harvest now, decrypt later” – traffic captured today can be decrypted once the technique exists, so it is not a distant-future concern.