Witness Encryption with (Weak) Unique Decryption and Message Indistinguishability: Constructions and Applications

In this paper, we investigate WE scheme with the unique decryption and message indistinguishability, as well as its compelling applications. Our contributions are three-fold: (i) we first propose the notion of WE with MI and weak unique decryption, and give a construction based on public-coin differing-inputs obfuscation (diO), pseudorandom generator, and the Goldreich-Levin hard-core predicate; (ii) We show that our WE with MI and weak unique decryption can be used to construct a 4-round non-black-box honest-verifier zero-knowledge argument protocol; and (iii) We present a WE scheme with unique decryption and MI based on public-coin diO and weak auxiliary input multi-bit output point obfuscation (AIMPO). Moreover, we show that using our WE with unique decryption, we can get rid of the limitation of honest-verifier zero-knowledge property, thus yielding a 4-round non-black-box zero-knowledge argument.