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Identity-based Cryptography (IBC) is an exciting alternative to public-key Cryptography (PKC), as it eliminates the need for certificate that is a major issue in PKC. However, IBC suffers from an additional limitation viz. the key escrow problem - that is - a user's private key is generated by the central trusted Key Generation Centre (KGC) - that being a single entity, lends itself to the security vulnerabilities in the cryptosystem. One of the prominent solutions proposed as Secure Key Issuing Protocol by Lee. et al. which uses a distributed protocol to generate the private key for user. However, this approach entails significant communications overhead. Hence, in this paper we have proposed an improved Identity based Secure Key Generation Protocol that gives the complete solution of key escrow problem, using clustering based approach. The proposed scheme involves less number of authorities in the computation of the public/private key pair and hence is more efficient. As we further analyze in the paper, our protocol also provides protection against the possible collusion attack in Lee's protocol. To the best of our knowledge, this is a simple, yet efficient and unique attempt to overcome the key escrow problem in IBCs.
Date of Conference: 15-17 Sept. 2011