A key recovery attack on MDPC with CCA security using decoding errors

Forskningsoutput: Kapitel i bok/rapport/Conference proceedingKonferenspaper i proceeding


Algorithms for secure encryption in a post-quantum world are currently receiving a lot of attention in the research community, including several larger projects and a standardization effort from NIST. One of the most promising algorithms is the code-based scheme called QC-MDPC, which has excellent performance and a small public key size. In this work we present a very efficient key recovery attack on the QCMDPC scheme using the fact that decryption uses an iterative decoding step and this can fail with some small probability. We identify a dependence between the secret key and the failure in decoding. This can be used to build what we refer to as a distance spectrum for the secret key, which is the set of all distances between any two ones in the secret key. In a reconstruction step we then determine the secret key from the distance spectrum. The attack has been implemented and tested on a proposed instance of QC-MDPC for 80 bit security. It successfully recovers the secret key in minutes. A slightly modified version of the attack can be applied on proposed versions of the QC-MDPC scheme that provides IND-CCA security. The attack is a bit more complex in this case, but still very much below the security level. The reason why we can break schemes with proved CCA security is that the model for these proofs typically does not include the decoding error possibility.


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Titel på värdpublikationAdvances in Cryptology - ASIACRYPT 2016 - 22nd International Conference on the Theory and Application of Cryptology and Information Security, Proceedings
Antal sidor27
Volym10031 LNCS
ISBN (tryckt)9783662538869
StatusPublished - 2016
Peer review utfördJa
Evenemang22nd Annual International Conference on the Theory and Applications of Cryptology and Information Security (ASIACRYPT), 2016 - Hanoi, Vietnam
Varaktighet: 2016 dec 42016 dec 8


NamnLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
Volym10031 LNCS
ISSN (tryckt)03029743
ISSN (elektroniskt)16113349


Konferens22nd Annual International Conference on the Theory and Applications of Cryptology and Information Security (ASIACRYPT), 2016

Relaterad forskningsoutput

Qian Guo, 2016, Department of Electrical and Information Technology, Lund University. 243 s.

Forskningsoutput: AvhandlingDoktorsavhandling (sammanläggning)

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