Cryptanalysis of LEDAcrypt

Published

September 16, 2020

Author(s)

Daniel C. Apon, Ray A. Perlner, Angela Y. Robinson, Paulo Santini

Abstract

We report on the concrete cryptanalysis of LEDAcrypt, a 2nd Round candidate in NIST's Post- Quantum Cryptography standardization process and one of 17 encryption schemes that remain as candidates for near-term standardization. LEDAcrypt consists of a public-key encryption scheme built from the McEliece paradigm and a key-encapsulation mechanism (KEM) built from the Niederreiter paradigm, both using a quasi- cyclic low-density parity-check (QC-LDPC) code. In this work, we identify a large class of extremely weak keys and provide an algorithm to recover them. For example, we demonstrate how to recover $1$ in $2^{47.72}$ of LEDAcrypt's keys using only $2^{18.72}$ guesses at the 256-bit security level. This is a major, practical break of LEDAcrypt. Further, we demonstrate a continuum of progressively less weak keys (from extremely weak keys up to all keys) that can be recovered in substantially less work than previously known. This demonstrates that the imperfection of LEDAcrypt is fundamental to the system's design.

Proceedings Title

Advances in Cryptology – CRYPTO 2020

Volume

12172

Conference Dates

August 16-20, 2020

Conference Location

Santa Barbara, CA

Conference Title

Crypto 2020

Pub Type

Conferences

Download Paper

https://doi.org/10.1007/978-3-030-56877-1_14

Local Download

Keywords

NIST PQC, LEDAcrypt, McEliece, QC-LDPC, Cryptanalysis

Citation

Apon, D. , Perlner, R. , Robinson, A. and Santini, P. (2020), Cryptanalysis of LEDAcrypt, Advances in Cryptology – CRYPTO 2020, Santa Barbara, CA, [online], https://doi.org/10.1007/978-3-030-56877-1_14 (Accessed July 1, 2025)