CheckScrambledPassword check scrambled password received from client.

Checks if a MySQL style caching_sha2 authentication string matches a password.

DecodePassword converts hex string password without prefix '*' to byte array.

EncodePassword converts plaintext password(type is string) to hashed hex string.

EncodePasswordBytes converts plaintext password(type is []byte) to hashed hex string.

Sha1Hash is an util function to calculate sha1 hash.

UserIdentity represents username and hostname.