A digital signature is a digital code that can be attached to an electronic message (email, spreadsheet, text file, etc.) to uniquely identify the sender and ensure authenticity and integrity of the document. Like a written signature, a digital signature guarantees that the person who claims to have sent a message is the one who sent it. Moreover, a digital signature also guarantees the message received is the one that was sent and has not been altered in any way since that person created it. An anonymous signature is a digital signature where the signature of a message does not reveal the identity of the signer. Anonymous signatures are useful in many applications where anonymity is required including key exchange protocols, anonymous transaction systems, auction systems and anonymous paper reviewing.
We present a new formalism of anonymous signature, where instead of the message as in previously presented schemes, a part of the signature is withheld to maintain anonymity. We introduce the notion of unpretendability to guarantee infeasibility for someone other than the correct signer to pretend authorship of the message and signature. Our definition retains applicability for all previous applications of the anonymous signature, provides stronger security, and is conceptually simpler. Finally, we provide a generic algorithm to transform any given digital signature scheme to an anonymous signature scheme which retains all the properties of the original digital signature scheme.
Dr. Vishal Saraswat finished Ph.D. in Cryptography in 2012 at Dept. of Mathematics, University of Minnesota, Minneapolis, USA. He had earlier completed M.S.from University of Minnesota in both Mathematics and Computer Science departments. He was a visiting faculty at IIT Hyderabad and currently holds the position of Assistant Professor at C.R.Rao Advanced Institute of Mathematics, Statistics and Computer Science. His research interests are in Number Theory and Cryptography, Computer and Information Security, Algorithm Design and Analysis, Computational Complexity and Financial Mathematics.