This is just a heads up for those who remotely log in to their Mac using SSH and public key authentication.
The current public beta of Ventura ships with OpenSSH_9.0p1. According to the OpenSSH release notes:
This release disables RSA signatures using the SHA-1 hash algorithm
by default. This change has been made as the SHA-1 hash algorithm is
cryptographically broken, and it is possible to create chosen-prefix
hash collisions for <USD$50K
If you generated RSA keys using just ssh-keygen without specifying a key type you probably ended up with RSA signatures using the now deprecated SHA-1 hash algorithm. This will prevent you from logging in to your Mac with the public key.
A workaround is suggested in this Reddit thread: SSH in Ventura.
A better solution is to generate keys based on a more secure hash algorithm such as ed25519 which you can generate like this:
ssh-keygen -t ed25519 -C "comment"
The “comment” can be used to identify the machine on which the key was generated or anything else you want.
