A coworker of mine was reporting an issue with SSH after updating to Mac OS X High Sierra.
$ ssh server-alias-hostname Unable to negotiate with 192.168.1.5 port 22: no matching cipher found. Their offer: blowfish-cbc,aes256-cbc
You can view a list of supported ciphers by running
ssh -Q cipher.
It turns out that the system is configured to use certain ciphers within
/etc/ssh/ssh_config. You can adjust your local configuration within
~/.ssh/config to make sure that the ciphers supported by your local client
match one of the ones offered by the remote server.
# ~/.ssh/config Host * SendEnv LANG LC_* Ciphers +aes256-cbc