Myriads of ultra-constrained 4-bit micro controllers (MCUs) are deployed in (mostly) legacy devices, some in security sensitive applications, such as remote access and control systems or all sort of sensors. Yet the feasibility and practicability of standardized cryptography on 4-bit MCUs has been mostly neglected. In this work we close this gap and provide, to the best of our knowledge, the first implementations of ECC and SHA-1, and the fastest implementation of AES on a 4-bit MCU. Though it is not the main focus of this paper, we have investigated the SCA resistance trade-offs for ECC by implementing a variety of countermeasures. We hope that our comprehensive, highly energy-efficient crypto library-that even outperforms all previously published implementations on low-power 8-bit MCUs-will give rise to a variety of security functionalities, previously thought to be too demanding for these ultra-constrained devices.

Laser fault injection is one of the strongest fault injection techniques. It offers a precise area positioning and a precise timing, allowing a high repeatability of experiments.In our paper we examine possibilities of laser-induced faults that could lead to instruction skips. After the profiling phase we were able to perform an attack on the last AddRoundKey operation in AES and to retrieve the secret key with just one faulty and correct ciphertext pair. Our experiments show very high degree of repeatability and 100% success rate with correct laser settings.

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Binary field multiplication is the most fundamental building block of binary field Elliptic Curve Cryptography (ECC) and Galois/Counter Mode (GCM). Both bit-wise scanning and Look-Up Table (LUT) based methods are commonly used for binary field multiplication. In terms of Side Channel Attack (SCA), bit-wise scanning exploits insecure branch operations which leaks information in a form of timing and power consumption. On the other hands, LUT based method is regarded as a relatively secure approach because LUT access can be conducted in a regular and atomic form. This ensures a constant time solution as well. In this paper, we conduct the SCA on the LUT based binary field multiplication. The attack exploits the horizontal Correlation Power Analysis (CPA) on weights of LUT. We identify the operand with only a power trace of binary field multiplication. In order to prevent SCA, we also suggest a mask based binary field multiplication which ensures a regular and constant time solution without LUT and branch statements.

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