Inception Makes Non-malleable Codes Stronger

Abstract. Non-malleable codes (NMCs), introduced by Dziembowski, Pietrzak and Wichs [DPW10], provide a useful message integrity guar-antee in situations where traditional error-correction (and even error-detection) is impossible; for example, when the attacker can completely overwrite the encoded message. NMCs have emerged as a fundamental object at the intersection of coding theory and cryptography. A large body of the recent work has focused on various constructions of non-malleable codes in the split-state model. Many variants of NMCs have been introduced in the literature i.e. strong NMCs, super strong NMCs and continuous NMCs. Perhaps the most useful notion among these is that of continuous non-malleable codes, that allows for continu-ous tampering by the adversary. In this paper we give the first efficient, information-theoretic secure con-struction of continuous non-malleable codes in 2-split-state model. En-route to our main result, we obtain constructions for almost all possible notion of non-malleable codes that have been considered in the split-state model, and for which such a construction is possible. Our result is ob-tained by a series of black-box reductions starting from the non-malleable codes from [ADL14]. One of the main technical ingredient of our result is a new concept that we call inception coding. We believe it may be of independent interest.