Some embodiments provide a method for a first device that identifies definitions of different groups of devices, each of which is defined by a set of properties required for a device to be a member. The method monitors properties of the first device to determine when the device is eligible for membership in a group. When the first device is eligible for membership in a first group of which the device is not a member, the method sends an application for membership in the first group signed with at least a private key of the device to at least one other device that is a member of the first group. When the first device becomes ineligible for membership in a second group of which the first device is a member, the method removes the device from the second group and notifies other devices that are members of the second group.