Time intervals for stateful signature production

A computing device 100 comprises: a memory 102 to store a set of states and a corresponding set of non-overlapping time intervals 104; a timing unit 106 to indicate a time at which a signature is to be produced; and a processor 108 to identify which time interval of the interval set includes the indicated time, generate a signing key 110 based on a state associated with the identified time interval, and produce a signature 112, under a stateful signature scheme, with the signing key. In response to an update received via an interface of the computing device, the processor may modify the mapping of set of states and corresponding time intervals. A duration of the time interval may be modified. A further device comprises an interface to receive a message, to which the signature is applied using the signing key. The time interval may be associated with a unique state.