SENDING AND RECEIVING MESSAGES

The present disclosure relates to the exchange of information between a message sending device and a message receiving device with message authentication and proposes to reduce the time required for message authentication by pre-computing a message tag, such as a MAC, and subsequently replacing the computation of the MAC when the tag is to be validated (or indeed also on sending) by a table look-up. The approach requires a set of messages and works particularly well for small sets of messages, for example as small as two or three messages, or less than five or ten messages. The approach finds particular application in control networks where control decisions have to be taken quickly and securely, for example in the control of a vehicle, for example an autonomous vehicle, or the control of a smart electricity grid.