Method and apparatus for exchanging messages

A method and to an apparatus for achieving cryptographic protection of a plurality of messages in a message exchange, for example, in particular the cryptographic protection being implemented by means of digital signatures and nonces is provided. The nonces are not transmitted directly, but rather can be reproducibly calculated from preceding messages, wherein a checksum of a previous message is also considered for each nonce. Consideration is implemented in such a way that cryptographical calculations in particular intended for the creation of the digital signature and the nonce may be calculated one single time and not separately for the nonce and the digital signature.