Ssh-keygen (command)

ssh-keygen is an OpenSSH software command used to generate, manage, and convert authentication keys. It support at least four different key types RSA, DSA, ECDSA and ed25519.

Commands

• ssh-keygen -l -f /etc/ssh/ssh_host_XXXXkey.pub
• ssh-keygen -vF host (-v flag added in OpenSSH 8.1)
• ssh-keygen -t ed25519 (There is no need to set the key size, as all Ed25519 keys are 256 bits) other options: [-t dsa | ecdsa | ed25519 | rsa]

Activities

1. Generate a public private key using ed25519 key format using the following command: ssh-keygen -t ed25519
2. Solve" "WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!" warning:

ssh-keygen -R SERVER_NAME -R Removes all keys belonging to hostname from a known_hosts file

ssh -oStrictHostKeyChecking=no SERVER_NAME Temporarily turning off host key checking

Both solutions have security implications.

1. Understand different key types: dsa, ecdsa, ed25519 and rsa

Related commands: ssh-copy-id

See also

• Certification Authority
• OpenSSH/OpenSSH versions Release Notes/ Changelog
• Kerberos
• Cisco IOS/Configure public RSA key authentication

http://man7.org/linux/man-pages/man1/ssh-keygen.1.html

https://www.openssh.com/txt/release-8.1