Cryptology ePrint Archive: Report 2017/476

Forward-Security under Continual Leakage

Mihir Bellare and Adam O'Neill and Igors Stepanovs

Abstract: Current signature and encryption schemes secure against continual leakage fail completely if the key in any time period is fully exposed. We suggest forward security as a second line of defense, so that in the event of full exposure of the current secret key, at least uses of keys prior to this remain secure, a big benefit in practice. (For example if the signer is a certificate authority, full exposure of the current secret key would not invalidate certificates signed under prior keys.) We provide definitions for signatures and encryption that are forward-secure under continual leakage. Achieving these definitions turns out to be challenging, and we make initial progress with some constructions and transforms.

Category / Keywords: public-key cryptography / leakage-resilient cryptography, forward security, digital signatures, public-key encryption

Date: received 28 May 2017

Contact author: istepano at eng ucsd edu

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Version: 20170529:163338 (All versions of this report)

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