Secure Obfuscation of Encrypted Verifiable Encrypted Signatures

Abstract

Since obfuscation was brought into the field of cryptography, it has become one of the most difficult and hottest problems. Because a general secure obfuscating method, if exists, will lead to the solution of many open problems in cryptography. However, after Bark et al.’s negative impossibility result for general obfuscation became well-known, only a few positive results was brought out. In $\emph{EUROCRYPT 2010}$, Hada proposed a secure obfuscator of encrypted signatures (ES), which signs a message under Alice’s secret signing key and then encrypts the signature using Bob’s public encryption key. This result is the only few secure obfuscation of complicated cryptographic primitives. In this paper, we consider the obfuscation of encrypted verifiable encrypted signatures (EVES). There is a trusted third party (TTP) in our protocol, and EVES first generates a verifiable encrypted signature (VES) under Alice’s secret signing key and the TTP’s public encryption key and then the VES is encrypted using Bob’s public encryption key. We give out the detailed EVES protocol and securely obfuscate it. We prove the security requirement of virtual black box property under standard assumptions and the secure obfuscation result will have many practical applications as we issue.