A tamper-resistant package for protecting information stored in electronic circuitry is described. An energy source provides energy (electrical current, optical energy, microwave energy or RF energy, for example) within a region occupied by the circuitry to be protected. The energy is applied to an energy distribution system comprising a path or paths for energy distribution. Sensing means are provided which respond to the distribution system for sensing an intrusion. The distribution system includes an arrangement for changing or altering the path or paths over which the energy travels or altering the topology of the path or paths. The sensing means is informed of the appearance of the distribution system and senses an intrusion by comparing the appearance of the path(s) with the predicted appearance. In one embodiment, electrical current is selectively applied to a subset of electrical conductors. The pattern of current flowing in the conductors is sensed and compared to an expected pattern which is determined by the subset of energized conductors. Intrusion is evidenced by a disparity between the pattern of energized paths sensed by the sensing means compared to the pattern predicted by the sensing means. Dynamically varying the identity of the energized paths makes it difficult for an attacker to bypass the tamper detection.