1. A computer implemented method for verifying membership in one or more sets that are subsets of a global set, the method compromising: representing members of the global set by mapping each member to a distinct Boolean variable of length d, wherein 2 d is not less than the number of members in the global set; representing a subset of the global set by a Boolean expression which evaluates to a first value for any of the assignments to the Boolean variables which represent members of the subset, and which evaluates to a second value for any of the assignments to the Boolean variables which represent members of the global set that are not members of the subset, wherein the Boolean expression is constructed from one or more subsets so as to be evaluated efficiently for any assignment to the Boolean variables which represent members of the global set; and determining membership of a target member of the global set in a target subset of the global set by evaluating the Boolean expression that represents the target subset based on the mapping of the target member.