SSH public key authentication rejected with debug message: no mutual signature algorithm

ssh user@remote-server -vvvv

debug1: no mutual signature algorithm

Cause

The RSA SHA-1 hash algorithm is being quickly deprecated across operating systems and SSH clients because of various security vulnerabilities, with many of these technologies now outright denying the use of this algorithm.

Solution

Generate SSH key using ED25519 algorithm:

ssh-keygen -t ed25519

See also

• SSH-RSA key rejected with message "no mutual signature algorithm"
• Debugging SSH public key authentication problems