This paper constructs high-rate non-malleable codes in the information-theoretic plain model against tampering functions with bounded locality. We consider δ-local tampering functions; namely, each output bit of the tampering function is a function of (at most) S input bits. This work presents the first explicit and efficient rate-1 non-malleable code for δ-local tampering functions, where δ = ξ lg n and ξ < 1 is any positive constant. As a corollary, we construct the first explicit rate-1 non-malleable code against NC° tampering functions. Before our work, no explicit construction for a constant-rate non-malleable code was known even for the simplest 1-local tampering functions. Ball et al. (EUROCRYPT-2016), and Chattopadhyay and Li (STOC-2017) provided the first explicit non-malleable codes against δ-local tampering functions. However, these constructions are rate-0 even when the tampering functions have l-locality. In the CRS model, Faust et al. (EUROCRYPT-2014) constructed efficient rate-1 non-malleable codes for δ = O(log n) local tampering functions. Our main result is a general compiler that bootstraps a rate-0 non-malleable code against leaky input and output local tampering functions to construct a rate-1 non-malleable code against ξ lg n-local tampering functions, for any positive constant ξ < 1. Our explicit construction instantiates this compiler using an appropriate encoding by Ball et al. (EUROCRYPT-2016).
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