A Side-Channel Assisted Cryptanalytic Attack Against QcBits

Abstract

QcBits is a code-based public key algorithm based on a problem thought to be resistant to quantum computer attacks. It is a constanttime implementation for a quasi-cyclic moderate density parity check (QC-MDPC) Niederreiter encryption scheme, and has excellent performance and small key sizes. In this paper, we present a key recovery attack against QcBits. We first used differential power analysis (DPA) against the syndrome computation of the decoding algorithm to recover partial information about one half of the private key. We then used the recovered information to set up a system of noisy binary linear equations. Solving this system of equations gave us the entire key. Finally, we propose a simple but effective countermeasure against the power analysis used during the syndrome calculation.

Optimized implementation of QC‐MDPC code‐based cryptography

“…Most of the works related to QcBits implementation are research on side‐channel attacks. Rossi et al presented a side‐channel power‐based attack against the syndrome calculation of QcBits on Atmel AVR XMEGA128. The attack exploited a power leakage at the store of the rotated codeword (line 4 of Algorithm 3).…”

“…The QcBits implementation was provided in two versions: ref, which uses only the C code, and clmul, which performs arithmetic using the 128‐bit carry‐less multiplication instruction. Although the original implementations are fully constant time, they are vulnerable to other side‐channel attacks based on power consumption . Besides the mitigation of such side‐channel vulnerabilities, QcBits also needs some performance improvements to achieve a competitive performance level.…”

“…Although the original implementations are fully constant time, they are vulnerable to other side-channel attacks based on power consumption. 8 Besides the mitigation of such side-channel vulnerabilities, QcBits also needs some performance improvements to achieve a competitive performance level. While most of the works derived from it concern cryptanalysis and theoretical alternatives, the development of implementation techniques has not yet been properly approached.…”

Optimizing the Decoding Process of a Post-Quantum Cryptographic Algorithm

“…The QcBits implementation was provided in two versions: ref, which uses only C code, and clmul, which performs arithmetic using the 128-bit carry-less multiplication instruction. Although the original implementations are fully constanttime, they are vulnerable against other side-channel attacks based on power consumption [Rossi et al 2017].…”

Melhorando o ataque de reação contra o QC-MDPC McEliece

“…O primeiro é um trabalho apresentado na conferência PQCRYPTO O segundo é um trabalho apresentado na conferência CHES por Rossi et al [RHHM17], que mostra um ataque por canal lateral a uma implementação do QC-MDPC McEliece, chamada QcBits [Cho16]. Depois de recuperar a informação sobre a chave usando um canal lateral, os autores mostraram como recuperar a chave usando uma relação linear entre os blocos da chave privada.…”