Skip to main content


On the linearization of human identification protocols: Attacks based on linear algebra, coding theory and lattices


Hassan Asghar, Ron Steinfeld, Shujun Li, Dali Kaafar and Josef Pieprzyk


Monash University

University of Surrey

Queensland University of Technology


Human identification protocols are challenge-response protocols that rely on human computational ability to reply to random challenges from the server based on a public function of a shared secret and the challenge to authenticate the human user. One security criterion for a human identification protocol is the number of challenge-response pairs the adversary needs to observe before it can deduce the secret. In order to increase this number, protocol designers have tried to construct protocols that cannot be represented as a system of linear equations or congruences. In this paper, we take a closer look at different ways from algebra, lattices and coding theory to obtain the secret from a system of linear congruences. We then show two examples of human identification protocols from literature that can be transformed into a system of linear congruences. The resulting attack limits the number of authentication sessions these protocols can be used before secret renewal. Prior to this work, these protocols had no known upper bound on the number of allowable sessions per secret.

BibTeX Entry

    journal          = {IEEE Transactions on Information Forensics and Security},
    author           = {Asghar, Hassan and Steinfeld, Ron and Li, Shujun and Kaafar, Dali and Pieprzyk, Josef},
    number           = {8},
    month            = apr,
    volume           = {10},
    year             = {2015},
    keywords         = {cryptographic protocols, human identification protocols, linear congruences},
    title            = {On the Linearization of Human Identification Protocols: Attacks based on Linear Algebra, Coding
                        Theory and Lattices},
    pages            = {1643--1655},
    address          = {Warsaw, Poland}