Laser Fault Injection Attacks against Radiation Tolerant TMR Registers

Security requirements for the Internet of things (IoT), wireless sensor nodes, and other wireless devices connected in a network for data exchange are high. Confidentiality, data integrity, availability of the services, and authentication of communicated devices are the main security goals usually implemented with cryptographic approaches. Their secrecy is based on the used keys. Theoretically, the cryptographic approaches are secure. This changes dramatically if an attacker has physical access to the attacked device. The execution time of cryptographic operations, current drawn from the power supply, electromagnetic radiation and many other physical effects, called side-channel effects, can be measured and later analysed using statistical or machine learning methods. Many attacks concentrate on the analysis of registers' activity. Some attacks exploit the key-dependent hamming weight of the data, stored in registers, and require usually many traces for the analysis [1]. Other attacks exploit the distinguishability of the registers addressing and can be successful when analysing many traces [2] as well as a single trace only [3], [4]. The sensitivity of cryptographic chips to the environmental and operating parameters - temperature, voltage, frequency, light, EM pulses, radiation, etc. - can be successfully exploited to reveal the cryptographic key too. A fluctuation of the environment and working parameters can cause fault(s). Cryptographic keys can be revealed by analysing such faults, whereby the mostly attacked blocks of cryptographic designs are the registers. Optical FI attacks using lasers belong to the class of semiinvasive attacks. This type requires to perform a chip decapsulation and exploits the sensitivity of semiconductors to the visible light. The pioneering work regarding optical FI attacks was published already in 2002 [5].