QuadSeal: Quadruple algorithmic symmetrizing countermeasure against power based side-channel attacks

Power based side-channel attacks attempt to obtain the secret key from implementations of cryptographic algorithms, such as Advanced Encryption Standard (AES), by analyzing the power traces during execution. Such attacks employ statistical methods to find correlations of power traces with parts of the secret key. In order to be effective, a countermeasure must remove or conceal such a signature. Previous countermeasures have either removed dynamic power signatures or leakage power signatures, but have not demonstrated effectiveness against both. In this paper, for the first time, we propose a balance and rotate technique for block cipher based algorithms and demonstrate it on an AES circuitry to remove the signature of the secret key from both the static and dynamic components of the power traces and further demonstrate that the countermeasure can withstand the path imbalances and process variation effects. Our solution, relies on algorithmically balancing Hamming distances and Hamming weights (where the bit transitions on the registers and gates are balanced, and the total number of 1s and 0s are balanced) by the use of four identical circuits with differing inputs and modified SubByte tables. By randomly rotating the four encryptions, the system is protected against variations, path imbalances and aging effects. When resistance against power analysis attacks is not of high priority, the proposed countermeasure allows components to be switched off to save power, or to run four executions in parallel for high performance. The proposed countermeasure is implemented for AES and tested against CPA and MIA attacks (for up to a million traces) and none of the secret keys were found even after one million power traces (unprotected AES circuit revealed the secret key within 5,000 power traces). This is the smallest known circuit which is capable of withstanding power based side-channel attacks when variations, path imbalances and aging effects are considered.