US Patent 7900248 Access control negation using negative groups

The subject disclosure pertains to systems and methods that facilitate managing groups entities for access control. A negative group is defined using a base group, where the negative group associated with a base group includes any entities not included in the base group. Negative groups can be implemented using certificates rather than explicit lists of negative group members. A certificate can provide evidence of membership in the negative group and can be presented for evaluation to obtain access to resources. Subtraction groups can also be used to manage access to resources. A subtraction group can be defined as the members of a first group, excluding any members of a second group.