Abstract: A sending device prepares a key for each electronic message sent by the device by applying an algorithm to specified data in the message and then incorporates the key in the message. A receiving device, upon receipt of an electronic message, locates the incorporated key and the data from which a sending device practicing the invention would have prepared it. The receiving device communicates a confirmation request to the purported sending device which contains the key and the data for its preparation. The sending device receives the confirmation messages and prepares a comparison key by applying the algorithm to the data in the confirmation request. The sending device replies to the confirmation request confirming that the sending device sent the message if the comparison key matches the key in the confirmation request and otherwise responds with a denial.

Abstract: A sending device locates and stores identifying information for each electronic message sent by the device. A receiving device, upon receipt of an electronic message, locates identifying information for the electronic message and the purported sending device of the message. The receiving device communicates a confirmation request to the purported sending device which contains identifying information for the message. The sending device receives confirmation messages and replies to such messages confirming that the message was sent if identifying information in the confirmation request corresponds to identifying information stored by the sending device and denying that the message was sent if the identifying information in the confirmation request does not correspond to stored data.

Abstract: A sending device locates and stores identifying information for each electronic message sent by the device. A receiving device, upon receipt of an electronic message, locates identifying information for the electronic message and the purported sending device of the message. The receiving device communicates a confirmation request to the purported sending device which contains identifying information for the message. The sending device receives confirmation messages and replies to such messages confirming that the message was sent if identifying information in the confirmation request corresponds to identifying information stored by the sending device and denying that the message was sent if the identifying information in the confirmation request does not correspond to stored data.

Abstract: A sending device prepares a key for each electronic message sent by the device by applying an algorithm to specified data in the message and then incorporates the key in the message. A receiving device, upon receipt of an electronic message, locates the incorporated key and the data from which a sending device practicing the invention would have prepared it. The receiving device communicates a confirmation request to the purported sending device which contains the key and the data for its preparation. The sending device receives the confirmation messages and prepares a comparison key by applying the algorithm to the data in the confirmation request. The sending device replies to the confirmation request confirming that the sending device sent the message if the comparison key matches the key in the confirmation request and otherwise responds with a denial.