04159468 is referenced by 125 patents and cites 7 patents.

A device for insertion in a communications line for verifying message integrity within a significant portion of existing communications networks. At the transmitter end, the device receives plain text messages from the communications line, generates an authentication field by encrypting the plain text message received and retransmits the plain test message received, with the authentication field appended thereto, onto the communications line.

At the receiver end, the device receives messages from the communications line, generates an authentication field by encrypting the plain text portion of the message received and compares the authentication field generated with the authentication field appended to the plain text portion of the message received. If the two authentication fields are identical, the plain text message has been received exactly as it was transmitted, and the receiving device will transmit the plain text portion of the message received to the receiving terminal, appending thereto a character indicating message integrity. Similarly, if the two authentication fields differ, the receiving device will transmit to the receiving terminal the plain text portion of the message received with an appended status character indicating that an error occurred during transmission of the plain text portion of the message. If a message is received without an authentication field appended thereto, the receiving device will transmit the plain text message received with an appended character indicating that the integrity status of the message received is unknown.

Title
Communications line authentication device
Application Number
5/852446
Publication Number
4159468
Application Date
November 17, 1977
Publication Date
June 26, 1979
Inventor
Carl M Campbell Jr
Newtown Square
PA, US
Harold F Gibson
Downington
PA, US
Thomas J Dodds Jr
Drexel Hill
PA, US
Vera L Barnes
Wayne
PA, US
Agent
Mark T Starr
Assignee
Burroughs Corporation
MI, US
IPC
H04L 1/10
View Original Source