Security analysis and improvement for key issuing schemes in ID-based cryptography

Sae-Ran Kwon, Sangho Lee

Feng Cao, Zhenfu Cao, Licheng Wang

At TCP ADS 2005, Sui et al. proposed a novel separable and anonymous ID-based key issuing scheme without secure channel, and claimed the key-escrow problem has been solved. In this paper, we present a security analysis on their schemes and point out that their two protocols are not secure and they do not solve the key-escrow problem. Further, we present an improved key issuing protocol which is proved to be secure against adaptive chosen message attack without the random oracle model under the q - SDH assumption

Nuttapong Attrapadung, Yang Cui, David Galindo +6 more

HE Da-ke

A more security analysis on the ID-based Authenticated Group Key Agreement(ID-AGKA) is given and it is found that the ID-based AGKA does not resist outsider attack, that is, an adversary can make a group session key inconsistent, which can not be detected by the users in the group however. An improvement of the AGKA scheme is proposed. Security analysis shows the scheme can resist outside attack.

Shengbao Wang, Zhenfu Cao, Haiyong Bao

Dhruti P. Sharma, Devesh C. Jinwala

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.