Method for implementing strict monotonic numerator to securely transfer e.g. critical messages from transmitter to receiver in motor car, involves incrementing counter value until counter value is equal to or larger than stored value

摘要

The method involves saving a sum of an initial value of a strictly monotonic numerator (56) and a constant value (62) as a stored value in a storage unit i.e. non volatile storage unit (58), where the stored value is used as initial value. The counter value incremented in an occurrence of a certain event until the counter value is equal to or larger than the stored value. A set of codes is assigned with a message that is exchanged between a transmitter (52) and a receiver (54). The codes are computed under consideration of the message and the counter value by using a key. An independent claim is also included for an arrangement for providing a strict monotonic numerator.