Algorithm to Design Conductive Mesh for Tamperproof Envelope

Protection of the Critical Security Parameters is a permanent concern for the designers, but also for the users of cryptographic equipment. The usage of a conductive mesh is a sensitive and efficient solution in order to protect the firmware, keys or any other sensitive data that could be contained in a cryptographic module. In order to improve the security provided by this principle, based on the flexibility of common technology that can be used to produce PCBs, an algorithm to produce particular designs of conductive mesh on PCBs starting from random bit strings is present in this article. Random design of conductive mesh is useful in order to increase the unpredictability of its electrical characteristics so, in addition to the sensitivity of this conductive mesh which will detect and react even to any attempt of measuring it by probes, an attacker will not have any information which can be exploited. The proposed innovative algorithm provides filling of the full area of envelope which cover the cryptographic module, even if its perimeter is irregular, according to necessary dimensions and profile, keeping traces on a dense grid, without any uncovered areas. The main advantage of the proposed solution consists of the possibility to implement a fully automated production flux, without human participation, and with an increased level of security due to unpredictable electrical characteristics of conductive mesh generated from a true random bit string.