The WRONG Way: Double Hashing & Wacky Hash Functions Here are some examples of poor wacky hash functions I've seen suggested in forums on the internet. md5(sha1(password)) md5(md5(salt) + md5(password)) sha1(sha1(password)) sha1(str_rot13(password + salt)) md5(sha1(md5(md5(password) + sha1(password)) + md5(password))) Do not use any of these.