## Cryptology ePrint Archive: Report 2021/320

Binding BIKE errors to a key pair

Nir Drucker and Shay Gueron and Dusan Kostic

Abstract: The KEM BIKE is a Round-3 alternative finalist in the NIST Post-Quantum Cryptography project. It uses the FO$^{\not \bot}$ transformation so that an instantiation with a decoder that has a DFR of $2^{-128}$ will make it IND-CCA secure. The current BIKE design does not bind the randomness of the ciphertexts (i.e., the error vectors) to a specific public key. We propose to change this design, although currently, there is no attack that leverages this property. This modification can be considered if BIKE is eventually standardized.

Category / Keywords: public-key cryptography / BIKE, Post-Quantum Cryptography, NIST, QC-MDPC codes, Ciphertext Binding