Zero-Knowledge Protocols for the McEliece Encryption

Abstract

We present two zero-knowledge protocols for the code-based McEliece public key encryption scheme in the standard model. Consider a prover who encrypted a plaintext m into a ciphertext c under the public key pk. The first protocol is a proof of plaintext knowledge (PPK), where the prover convinces a polynomially bounded verifier on a joint input (c,pk) that he knows m without actually revealing it. This construction uses code-based Veron's zero-knowledge identification scheme. The second protocol, which builds on the first one, is a verifiable McEliece encryption, were the prover convinces a polynomially bounded verifier on a joint input (c,pk,m) that c is a valid encryption of m, without performing decryption. These protocols are the first PPK and the first verifiable encryption for code-based cryptosystems.