Keychain helps you securely manage your SSH and GPG private keys. As a frontend
to ssh-agent and gpg-agent, it maintains a single, long-running agent per user
and host so you only have to enter your passphrases once per reboot.

By writing the agent's environment to per-host files, Keychain makes it
effortless for new shells and background cron jobs to securely access your
cached keys.
