ISSN : 1796-217X
Volume : 4    Issue : 3    Date : May 2009

Threshold Certificate-based Encryption
Yang Lu, Jiguo Li, and Junmo Xiao
Page(s): 210-217
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Certificate-based encryption (CBE) is a new asymmetric encryption paradigm which combines
traditional public-key encryption (PKE) and identity based encryption (IBE) while preserving some of
their most attractive features. CBE provides an efficient implicit certificate mechanism to eliminate
third-party queries for the certificate status and to simply the certificate revocation problem.
Therefore, CBE can be used to construct an efficient PKI requiring fewer infrastructures. In addition,
it also solves the key escrow problem and key distribution problem inherent in IBE. In this paper, we
introduce a new notion called Threshold Certificate-Based Encryption (TCBE) to overcome the
limitations of CBE due to the using of sole master key in the system. It preserves the advantages of
CBE such as implicit certificate and no private key escrow. At the same time it inherits the properties
of threshold encryption. We first formalize the definition and security model for TCBE. Then we
propose a concrete TCBE scheme and prove it to be CCA-secure under the Decisional Bilinear
Diffie-Hellman assumption in the standard model.

Index Terms
threshold certificate-based encryption, security model, CCA-secure, standard model