The use of secret-key techniques in forward information verification

The theory of secret-key authentication techniques for verification of information is discussed, using authentication in pre-paid energy systems as an example. Since in a pre-paid system there is no reverse channel to the transmitter, the data must be checked by an appended authenticity code. Several types of cryptographic attacks are possible in general authentication systems. In the pre-paid energy system the user has additionally the means to carry out a chosen-plaintext attack. The theoretical basis for the design of the authentication code is investigated