Decrypting a Key
If you want to decrypt your SSH key, run the following command:
openssl rsa -in \ [existing name] \ -out \ [new unencrypted file name]
Encrypting a Key
If you want to encrypt your currently non-encrypted key, then run the following command instead:
aes256 openssl rsa -aes256 \ -in [existing name] \ -out [new unencrypted file name]
The example above encrypts using the aes256 algorithm. You can specify others by looking up the details here.