Extra dATa appended to a message which identifies and authenticATes the sender and message dATa using public-key encryption. The sender uses a one-way hash function to generATe a hash-code of about 32 bits from the message dATa. He then encrypts the hash-code with his privATe key. The receiver recomputes the hash-code from the dATa and decrypts the received hash with the sender' s public key. If the two hash-codes are equal, the receiver can be sure thAT dATa has not been corrupted and thAT it came from the given sender. (1995-02-07)