Séminaire de Cryptographie

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Hervé Talé Kalachi

Improved Cryptanalysis of Rank Metric Schemes Based on Gabidulin Codes.

In this presentation, we prove that any variant of the GPT cryptosystem which uses a right column scrambler over the extension field as advocated by the works of Gabidulin et al. with the goal to resist to Overbeck’s structural attack are actually still vulnerable to that attack. We show that by applying the Frobenius operator appropriately on the public key, it is possible to build a Gabidulin code having the same dimension as the original secret Gabidulin code but with a lower length. In particular, the code obtained by this way correct less errors than the secret one but its error correction capabilities are beyond the number of errors added by a sender, and consequently an attacker is able to decrypt any ciphertext with this degraded Gabidulin code. A joint work with Ayoub OTMANI and Selestin NDJEYA.