An attack on a NIST proposal: RankSign, a code-based signature in rank metric

04/07/2018

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by   Thomas Debris-Alazard, et al.

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RankSign is a code-based signature scheme proposed to the NIST competition for post-quantum cryptography AGHRZ17. It is based on the rank metric and enjoys remarkably small key sizes, about 10KBytes for an intended level of security of 128 bits. It is also one of the fundamental blocks used in the rank metric identity based encryption scheme GHPT17. Unfortunately we will show that all the parameters proposed for this scheme in AGHRZ17 can be broken by an algebraic attack that exploits the fact that the augmented LRPC codes used in this scheme have very low weight codewords.