Threshold Discernible Ring Signatures
A ring signature  demonstrates that the signer who produced it is among a group A of n people, called a ring. A signer may produce a ring signature on any ring A he is part of, arbitrarily without any setup procedure or the consent of anyone in A. Several extensions of ring signatures have been proposed in literature. Step out ring signatures introduced in  address the issue of a ring member proving that she is not the original signer of a message, in case of dispute. First we show that the scheme in  has several flaws and design a correct scheme and prove formally the security of the same. Then we use the basic constructs of our scheme to design a protocol for a new problem, which we refer to as threshold discernible ring signatures. In threshold discernible ring signatures, a group B of t members can co-operate to identify the original signer of a ring signature that involved a group A of n alleged signers, where B ⊆ A and n ≥ t. This is the first time that this problem is considered in the literature. We formally prove the security of our scheme in the random oracle model and propose various extensions.
KeywordsEncryption Scheme Original Signer Ring Signature Discrete Logarithm Discrete Logarithm Problem
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