Paper 2013/716

A Secure Obfuscator for Encrypted Blind Signature Functionality

Xiao Feng and Zheng Yuan

Abstract

This paper introduces a new obfuscation called obfuscation of encrypted blind signature. Informally, Alice is Signer and Bob is User. Bob needs Alice to sign a message, but he does not want Alice to know what the message is. Furthermore, Bob doesn't want anyone to know the interactive process. So we present a secure obfuscator for encrypted blind signature which makes the process of encrypted blind signature unintelligible for any third party, while still keeps the original encrypted blind signature functionality. We use schnorr's blind signature scheme and linear encryption scheme as blocks to construct a new obfuscator. Moreover, we propose two new security definition: blindness w.r.t encrypted blind signature (EBS) obfuscator and one-more unforgeability(OMU) w.r.t EBS obfuscator, and prove them under Decision Liner Diffie-Hellman(DL) assumption and the hardness of discrete logarithm, respectively. We also demonstrate that our obfuscator satisfies the Average-Case Virtual Black-Box Property(ACVBP) property w.r.t dependent oracle, it is indistinguishable secure. Our paper expands a new direction for the application of obfuscation.