Generates a new key in the old format.
public func generateLegacy(username: String, bits: Int32, password: String, expires: Int32) throws -> Void
Use this method when you need to generate an RSA key in the old (PGP 2.6.x) format.
Username specifies the user of the key, Bits is the key length in bits. Provide Password for the key and its expiration date and time via Expires.
Only use this method where you want to work with very old PGP software. While still providing a decent level of protection (subject to key length, of course), legacy keys are rarely used these days, and have almost everywhere been replaced with new-style keys.
Most modern PGP implementations work with pairs of keys: the sign-only primary key and the encrypt-only (or encrypt-and-sign) subkey. If you need to generate a conformant PGP key to use with other PGP software, you likely need to use the GeneratePair method.