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On the Existence of Weak Keys for QC-MDPC Decoding

Abstract : We study in this work a particular class of QC-MDPC codes for which the decoding failure rate is significantly larger than for typical QC-MDPC codes of same parameters. Our purpose is to figure out whether the existence of such weak codes impacts the security of cryptographic schemes using QC-MDPC codes as secret keys. A class of weak keys was exhibited in [DGK19]. We generalize it and show that, though their Decoding Failure Rate (DFR) is higher than normal, the set is not large enough to contribute significantly to the average DFR. It follows that with the proper semantically secure transform [HHK17], those weak keys do not affect the IND-CCA status of key encapsulation mechanisms, like BIKE, which are using QC-MDPC codes.
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Contributor : Valentin Vasseur Connect in order to contact the contributor
Submitted on : Friday, February 12, 2021 - 11:30:43 AM
Last modification on : Friday, January 21, 2022 - 3:16:52 AM
Long-term archiving on: : Thursday, May 13, 2021 - 6:38:36 PM


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  • HAL Id : hal-03139708, version 1



Nicolas Sendrier, Valentin Vasseur. On the Existence of Weak Keys for QC-MDPC Decoding. 2020. ⟨hal-03139708⟩



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