I can only get Jenkins to talk to Gerrit's SSH connection if the key file has no password.

1. Use ssh-keygen to create a key with a password

2. Configure Gerrit Trigger with that key and its password

3. Test Connection

> Bad SSH keyfile or password

Jenkins.log:
> 09-Feb-2012 12:43:18 com.sshtools.j2ssh.transport.publickey.SshPrivateKeyFile parse
> INFO: Parsing private key file
> 09-Feb-2012 12:43:18 com.sshtools.j2ssh.transport.publickey.SshPrivateKeyFile parse
> INFO: Private key is not in the default format, attempting parse with other supported formats

4. Clear the password: ssh-keygen -f .ssh/id_rsa -p -N ''

Note that the Proc-Type and DEK-Info headers have gone.

5. Test connection (without clearing the password!)

6. Succeeds. Log still complains about non-default format.

7. Clear the password in Jenkins.

8. Test connection

9. Still succeeds, Log still complains about non-default format.

This took me ages to nail down because supplying a password to a no-password key file doesn't fail.