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A Timing Attack on the HQC Encryption Scheme

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Author(s):
Paiva, Thales Bandiera ; Terada, Routo ; Paterson, KG ; Stebila, D
Total Authors: 4
Document type: Journal article
Source: SELECTED AREAS IN CRYPTOGRAPHY - SAC 2019; v. 11959, p. 23-pg., 2020-01-01.
Abstract

The HQC public-key encryption scheme is a promising code-based submission to NIST's post-quantum cryptography standardization process. The scheme is based on the decisional decoding problem for random quasi-cyclic codes. One problem of the HQC's reference implementation submitted to NIST in the first round of the standardization process is that the decryption operation is not constant-time. In particular, the decryption time depends on the number of errors decoded by a BCH decoder. We use this to present the first timing attack against HQC. The attack is practical, requiring the attacker to record the decryption time of around 400 million ciphertexts for a set of HQC parameters corresponding to 128 bits of security. This makes the use of constant-time decoders mandatory for the scheme to be considered secure. (AU)

FAPESP's process: 14/50937-1 - INCT 2014: on the Internet of the Future
Grantee:Fabio Kon
Support Opportunities: Research Projects - Thematic Grants
FAPESP's process: 15/24485-9 - Future internet for smart cities
Grantee:Fabio Kon
Support Opportunities: Research Projects - Thematic Grants