Message sequence integrity provides proof that the ordering of a sequence of messages sent from an originator to a recipient has been preserved. This service counters message sequencing threats, such as the replaying and re-ordering of messages. It is provided on a per-recipient basis using symmetric or asymmetric encryption techniques.
To provide the service, the message originator generates a sequence number, which identifies the position of the message in the sequence. This number is transferred in the message token's signed-data, or if the secrecy of the number is required, in the token's encrypted-data. Each originator/recipient pair using this service maintains a distinct pair of sequence numbers. One drawback with the message sequence integrity service is that it requires all users to maintain pairwise sequence numbers with (potentially) all other users.