A Black-Box Construction of Non-Malleable Encryption from Semantically Secure Encryption

Abstract

We show how to transform any semantically secure encryption scheme into a non-malleable one, with a black-box construction that achieves a quasi-linear blow-up in the size of the ciphertext. This improves upon the previous non-black-box construction of Pass, Shelat and Vaikuntanathan (Crypto \u2706). Our construction also extends readily to guarantee non-malleability under a bounded-CCA2 attack, thereby simultaneously improving on both results in the work of Cramer et al. (Asiacrypt \u2707). Our construction departs from the oft-used paradigm of re-encrypting the same message with different keys and then proving consistency of encryption. Instead, we encrypt an encoding of the message; the encoding is based on an error-correcting code with certain properties of reconstruction and secrecy from partial views, satisfied, e.g., by a Reed-Solomon code