A multiplexed secure counter is provided, in which a multiplicity of child
secure counters are secured by a parent secure counter. Child counters
are stored with a parent secure counter value and a signature. Before a
child counter is read, the signature is verified and value stored is
checked against the current value of the parent secure value. If the
verifications are successful, the child secure counter can be used. To
increment a child counter, the signature is verified and the value stored
checked against the current value of the parent secure value. If the
verifications are successful, the parent counter and the child counter
are incremented, and the data is signed again.