Cryptology ePrint Archive: Report 1996/012

Proactive RSA

Yair Frankel, Peter Gemmell, Philip D. MacKenzie, Moti Yung

Abstract: We consider a "mobile adversary" which may corrupt all participants throughout the lifetime of the system in a non-monotonic fashion (i.e. recoveries are possible) but the adversary is unable to corrupt too many participants during any short time period. Schemes resiliant to such adverasry are called proactive. We present a proactive RSA system in which a threshold of servers applies the RSA signature (or decryption) function in a distributed manner. Employing new combinatorial and elementary number theoretic techniques, our protocol enables the dynamic updating of the servers (which hold the RSA key distributively); it is secure even when a linear number of the servers are corrupted during any time period; it efficiently "self-maintains" the security of the function and its messages (ciphertexts or signatures); and it enables continuous availability, namely, correct function application using the shared key is possible at any time.

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Publication Info: Appeared in the THEORY OF CRYPTOGRAPHY LIBRARY and has been included in the ePrint Archive.

Date: received Aug 5th, 1996.

Contact author: yair at cs sandia gov

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