International Association for Cryptologic Research

International Association
for Cryptologic Research


A Side-Channel Assisted Cryptanalytic Attack Against QcBits

Mélissa Rossi
Mike Hamburg
Michael Hutter
Mark E. Marson
DOI: 10.1007/978-3-319-66787-4_1
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Conference: CHES 2017
Abstract: 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.
  title={A Side-Channel Assisted Cryptanalytic Attack Against QcBits},
  booktitle={Cryptographic Hardware and Embedded Systems – CHES 2017},
  series={Lecture Notes in Computer Science},
  author={Mélissa Rossi and Mike Hamburg and Michael Hutter and Mark E. Marson},