Modification of Double Voter Perceptible Okamoto Blind Signature Based Electronic Voting Protocol

Three electronic voting protocols aiming double perceptibility were considered in this thesis. The most promising of them is double voter perceptible blind signature based electronic voting protocol proposed by Baseri et al. However, it is found that generally, the protocol might fail due to the selection of as generator of (where is a product of and ) by the certificate authority as such generator does not exist. Furthermore, were chosen as generators of and as generators of (where p and q are two large prime publicly known) by the certificate authority; thus, the modular p equality checks performed in the protocol might fail because used in their exponents are congruent modulo q and not congruent modulo Euler’s totient function of . These failures are shown by providing numerical counter-examples. We proposed the way of fixing these problems. Firstly, we modified one of these equalities such that can be selected randomly in . Moreover, we included the public key of the certificate authority with random value selected in in the message sent to the voting server by the voter; thus, identity of the voter is verified. Secondly, we selected in of order . This way, we might have different values as exponent on both sides of the equality but shall be congruent modulus p. Thus, all equality checks become valid. Lastly, we removed from the message sent to the ballot-counting server by the voting server since these are not used in revealing the identity of a dishonest voter. The modifications made retained all security properties of the protocol including the double perceptibility feature. Keywords: Electronic voting, double perceptibility, blind Signature, RSA crypto-system.