Method and device for data authentication in data communication environment

PURPOSE: To obtain an improved data processing system by generating a tag by combining plural cryptographic words and deciding an authentication tag used with data transfer in which a communication channel is used. CONSTITUTION: A message is signed by a transmitting origin 12 by a sign processing 22. A message 18, a transmitting origin identifier 26, a shared key 28 and a counter 30 are received by the processing 22. A message 24 with a signature is transmitted with a channel 20. A message 34 is received and an identifier 36 of a signer is extracted by inspecting the message 34 by a receiving destination 14. A value of the receiving destination itself of a key 38 of the receiving destination itself shared by a person who is provided with the identifier equal to the identifier 36 and a value of the receiving destination itself of a CTR 45 is looked up by using the identifier 36 by using a table 42 indexed by the identifier 36 by the receiving destination. After that, the message 34, the identifier 36, the key 38 and the CRT 45 are taken, inspection completion message 44 is recovered or the message 34 is judged to be forged by an inspection processing 43 and when the message 34 is judged to be forged, the message is discarded. COPYRIGHT: (C)1994,JPO