Patent ID: 7814314

Claim:
A computer-readable computer storage medium comprising computer-readable computer data for computer-implemented verification of validity and/or invalidity of one or more cryptographic digital certificates including a first digital certificate, each digital certificate certifying that a cryptographic key is associated with an entity, the computer data being for proving to a verifier computer system the validity or invalidity of at least the first digital certificate, the computer data comprising: (a) first data defining a plurality of sets, the plurality of sets comprising a first plurality of sets, wherein the first digital certificate belongs to each set in the first plurality; (b) for each set in at least the first plurality, second data which define period data for each of a plurality of periods of time and also define a first target for the set, wherein the first target is computable, in computer-implemented computation, from the period data for any one of said periods of time by the verifier computer system to verify the validity and/or invalidity of any certificate in the set relative to the respective period of time; wherein for each set in at least the first plurality, the period data form at least part of a hash tree, each period of time corresponding to the hash tree's node comprising the period data for the period of time, different periods of time corresponding to different nodes, wherein for at least two of the periods of time, one of the corresponding nodes is neither a child nor a parent of the other one of the corresponding nodes; (c) third data defining a second target computable, in computer-implemented computation, from the first targets of the first plurality of sets.