Preventing the Temperature Side Channel Attacks on Security Circuits

Security circuits are important parts of communication and data processing equipment. Nowadays technologies and computation power can be used in cryptanalytic attacks against these specialized pieces of equipment. Some collateral procedures have been developed to facilitate these attacks and they are called Side Channel Attacks. They force the physical limits of the logic circuits in order to provoke erroneous operations that will later help the cryptanalytic attacks. One of the most used side channel attack consists in forcing the security circuit to work at temperatures out of the operating limits or to quickly freeze it. Freezing at very low temperatures can block processors and memories with resident secret data stored in them. Later on, these data can be acquired and used in cryptanalytic attacks. This paper proposes a special conductive mesh that can act also as a temperature sensor. Besides its function to detect physical intrusions, its behavior at temperature variations makes it a very good detector of temperature side channel attacks. Considering that the conductive mesh is covering the security circuit, the active tamper detection circuit, which probes with signals and analyze the response of the conductive mesh, is capable of detecting more quickly the temperature variations than a temperature sensor located at the circuit board.