A Side-Channel Assisted Cryptanalytic Attack Against QcBits

Mélissa Rossi (1, 2, 3) , Mike Hamburg (4) , Michael Hutter (4) , Mark E Marson (4)

1 THALES COMMUNICATIONS & SECURITY
2 PSL - Université Paris Sciences et Lettres
3 CASCADE - Construction and Analysis of Systems for Confidentiality and Authenticity of Data and Entities
4 Rambus Cryptography Research Division [San Francisco]

QcBits is a code-based public key algorithm based on a problem thought to be resistant to quantum computer attacks. It is a constant-time 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.

Mots clés: Niederreiter; McEliece; Post-quantum cryptography; Learning parity with noise; Side-channel analysis; QcBits; Differential power analysis; Noisy binary linear equations; QC-MDPC codes

Domaines: Cryptographie et sécurité [cs.CR]

Mélissa Rossi, Mike Hamburg, Michael Hutter, Mark E Marson. A Side-Channel Assisted Cryptanalytic Attack Against QcBits. CHES 2017 - Conference on Cryptographic Hardware and Embedded Systems, Sep 2017, Taipei, Taiwan. pp.22, ⟨10.1007/978-3-319-66787-4_1⟩. ⟨hal-01614569⟩