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)