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TMPS: Ticket-Mediated Password Strengthening



John M. Kelsey, Dana Dachman-Soled, Meltem Sonmez Turan, Sweta Mishra


We introduce the notion of Ticket-Mediated Password Strengthening (TMPS), a technique for allowing users to derive keys from passwords while imposing a strict limit on the number of guesses of their password any attacker can make, and strongly protecting the users' privacy. We describe the security requirements of TMPS, and then a set of efficient and practical protocols to implement a TMPS scheme, requiring only hash functions, CCA2-secure encryption, and blind signatures. We provide several variant protocols, including an offline symmetric only protocol that uses a local trusted computing environment, and online variants that avoid the need for blind signatures in favor of group signatures or stronger trust assumptions. We formalize the security of our scheme by defining an ideal functionality in the Universal Composability (UC) framework, and by providing game-based definitions of security. We prove that our protocol realizes the ideal functionality in the random oracle model (ROM) under adaptive corruptions with erasures, and prove that security w.r.t. the ideal/real definition implies security w.r.t. the game-based definitions.
Proceedings Title
The Cryptographer's Track of the RSA Conference
Conference Dates
February 24-28, 2020
Conference Location
San Francisco, CA, US
Conference Title
The Cryptographer's Track of the RSA Conference (CT-RSA 2020)


Dictionary attacks, TMPS, Key derivation


Kelsey, J. , Dachman-Soled, D. , Sonmez Turan, M. and Mishra, S. (2020), TMPS: Ticket-Mediated Password Strengthening, The Cryptographer's Track of the RSA Conference, San Francisco, CA, US, [online],, (Accessed April 14, 2024)
Created February 13, 2020, Updated October 12, 2021