体验了ed25519 key的好处后实在不想回退回使用rsa key. 但升级到15.6后ssh-add无法添加ed25519 key, 原先的15.5则正常.
```sh
$ ssh-add ~/.ssh/my_ed25519
Enter passphrase for /home/chen/.ssh/my_ed25519:
Bad passphrase, try again for /home/chen/.ssh/my_ed25519:
Could not add identity "/home/chen/.ssh/my_ed25519": communication with agent failed
体验了ed25519 key的好处后实在不想回退回使用rsa key. 但升级到15.6后ssh-add无法添加ed25519 key, 原先的15.5则正常.
```sh
$ ssh-add ~/.ssh/my_ed25519
Enter passphrase for /home/chen/.ssh/my_ed25519:
Bad passphrase, try again for /home/chen/.ssh/my_ed25519:
Could not add identity "/home/chen/.ssh/my_ed25519": communication with agent failed
$ ssh -V
OpenSSH_7.5p1 Debian-5, OpenSSL 1.0.2l 25 May 2017
$ echo $SSH_AUTH_SOCK
/run/user/1000/keyring/ssh
```