super class for all Password Based Encryption (PBE) parameter generator classes.
converts a password to a byte array according to the scheme in PKCS12 (unicode, big endian, 2 zero pad bytes at the end).
converts a password to a byte array according to the scheme in PKCS5 (ascii, no padding)
converts a password to a byte array according to the scheme in PKCS5 (UTF-8, no padding)