You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: user_access_key.rb
    path of file: ./repos/identity-idp/app/services/encryption
    
    the code of the file until where you have to start completion: # UserAccessKey outputs various key hashing related to NIST encryption.
#
# Generate and store a 128-bit salt S.
# Z1, Z2 = scrypt(S, password)   # split 256-bit output into two halves
# Generate random R.
# D = KMS_GCM_Encrypt(key=server_secret, plaintext=R) xor Z1
# E = ha
    
    def transform_password_salt_to_scrypt_salt(salt)
      # Legacy passwords had 20 byte salts, so we took a SHA256 digest to get
      # to 32 bytes. While passwords exist with 20 byte salts, we will need this
      # line, otherwise the passwords are effectively expired.
      #
      # Also note that the salt arg will have a length of 64 chars since it is
      # a hex digest of 32 random bytes
      return OpenSSL::Digest::SHA256.hexdigest(salt) if salt.length != 64
      salt
    end