Cryptology ePrint Archive: Report 2013/876

Public-Key Encryption with Lazy Parties

Kenji Yasunaga

Abstract: In a public-key encryption scheme, if a sender is not concerned about the security of a message and is unwilling to generate costly randomness, the security of the encrypted message can be compromised. In this work, we characterize such \emph{lazy parties}, who are regraded as honest parties, but are unwilling to perform a costly task when they are not concerned about the security. Specifically, we consider a rather simple setting in which the costly task is to generate randomness used in algorithms, and parties can choose either perfect randomness or a fixed string. We model lazy parties as rational players who behave rationally to maximize their utilities, and define a security game between the parties and an adversary. Since a standard secure encryption scheme does not work in the setting, we provide constructions of secure encryption schemes in various settings.

Category / Keywords: public-key encryption, rational cryptography, lazy party

Original Publication (with major differences): SCN 2012

Date: received 29 Dec 2013, last revised 21 Dec 2015

Contact author: yasunaga at se kanazawa-u ac jp

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Version: 20151221:081620 (All versions of this report)

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