Cryptanalysis of a public-key encryption scheme based on the polynomial reconstruction problem

Abstract

We describe a cryptanalysis of a public-key encryption scheme based on the polynomial reconstruction problem, published at Eurocrypt 2003 by Augot and Finiasz. Given the public-key and a ciphertext, we recover the corresponding plaintext in polynomial time. Our technique is a variant of the Berlekamp-Welsh algorithm. We also describe a cryptanalysis of the reparation published by the authors on the IACR eprint archive, using a variant of the previous attack. Both attacks are practical as given the public-key and a ciphertext, one recovers the plaintext in a few minutes on a single PC. © International Association for Cryptologic Research 2004.