We recommend creating user keys at
least 1024 bits long. Protect your key with a good passphrase. Make
it lengthy and use a mixture of lowercase, uppercase, numeric, and
symbolic characters. Don't use words found in a dictionary.
Empty passphrases should be avoided unless you absolutely need to use
one, for example, in an automated batch script. [Section 18.104.22.168, "Using a plaintext key"]