Keychain (software)

Keychain is a password management utility available primarily on Unix-like operating systems, specifically designed to simplify SSH key management. It acts as a secure storage mechanism for SSH keys, allowing users to avoid repeatedly entering passphrases when connecting to remote servers via SSH.

Functionally, Keychain operates by storing SSH keys in memory after the user unlocks them with their passphrase. It then sets environment variables (SSH_AUTH_SOCK and SSH_AGENT_PID) that point to the running ssh-agent process, making the keys available to SSH clients. This eliminates the need to re-enter the passphrase for each new SSH session.

The program is typically invoked at login and can be configured to automatically start an ssh-agent process if one is not already running. It can also save the passphrase to the system's keyring (like Gnome Keyring or KDE Wallet) for even greater convenience, although this is a configuration option and not the default behavior.

Keychain supports multiple keys and can manage keys that are password protected or not. Its primary benefit is streamlining the SSH authentication process, making it more secure and efficient for users who frequently connect to remote servers. The software aims to provide a balance between security and usability in SSH key management.