On Perfect and Adaptive Security in Exposure-Resilient Cryptography

Abstract. We consider the question of adaptive security for two related cryptographic primitives: all-or-nothing transforms and exposureresilient functions. Both are concerned with retaining security when an intruder learns some bits of a string which is supposed to be secret: all-or-nothing transforms (AONT) protect their input even given partial knowledge of the output; exposure-resilient functions (ERF) hide their output even given partial exposure of their input. Both of these primitives can be defined in the perfect, statistical and computational settings and have a variety of applications in cryptography. In this paper, we study how these notions fare against adaptive adversaries, who may choose which positions of a secret string to observe on the fly. In the perfect setting, we prove a new, strong lower bound on the constructibility of (perfect) AONT. This applies to both standard and adaptively secure AONT. In particular, to hide an input as short as log n bits, the adversary...

• Type: Conference
• Year: 2001
• Where: EUROCRYPT
• Authors: Yevgeniy Dodis, Amit Sahai, Adam Smith
• Keywords: Adaptive, All-or-nothing Transforms, Cryptology, EUROCRYPT 2001, Related Cryptographic Primitives