In a secure communication employing keys which require updating, all parties
to
the communication update their keys according to a clock at a suitable agreed-upon
interval, and the keys are updated once each interval via a one-way function. The
key to be used for a communication is the one that is current when the communication
is established. In order to address clock-slip and slight timing differences across
a communication channel, each party to a paired communication send a current interval
index of their key to the other party. The remote index, i.e., the interval index
which is remote to the receiving party, is compared against the local interval
index, and the latter of the two interval indexes is used as the basis for generating
the key. The party with the earlier index must therefore update the key iteratively
until its index is concurrent with the later index. In addition, a public-key,
private-key pair is generated for the purpose of supporting key updating. To this
end, an escrow agent is provided to generate the public-key and private key-pair
and to distribute the public key to all parties wishing to engage in key updating,
while securing the private key.
