Cryptology ePrint Archive: Report 2009/421

How to Construct Identity-Based Signatures without the Key Escrow Problem

Tsz Hon Yuen and Willy Susilo and Yi Mu

Abstract: The inherent key escrow problem is one of the main reasons for the slow adoption of identity-based cryptography. The existing solution for mitigating the key escrow problem is by adopting multiple Private Key Generators (PKGs). Recently, there was a proposal that attempted to reduce the trust of the PKG by allowing a malicious PKG to be caught if he reveals the user's identity-based secret key illegally. Nonetheless, the proposal does not consider that the PKG can simply decrypt the ciphertext instead of revealing the secret key itself (in the case of identity-based encryption schemes).

The aim of this paper is to present an escrow-free identity-based signature (IBS) scheme, in which the malicious PKG will be caught if it releases a signature on behalf of the user but signed by itself. We present a formal model to capture such a scheme and provide a concrete construction.

Category / Keywords: public-key cryptography / Identity-based signature, key escrow

Publication Info: This is the full version of the paper in EuroPKI 2009.

Date: received 31 Aug 2009, last revised 24 Sep 2009

Contact author: thy738 at uow edu au

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Version: 20090925:020142 (All versions of this report)

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