Constructing secure proxy cryptosystem

Abstract

Proxy cryptosystem was first proposed by Mambo and Okamoto, for the delegation of the power to decrypt ciphertexts. However, to our knowledge, there is no reasonable mode aimed at this cryptographic notion. In this paper, we first present a practical mode: proxy cryptosystem based on time segmentation. Under this mode, a secure model is proposed and a proxy cryptosystem is constructed. Our construction uses ideas from the HIBE scheme of Gentry and Silverberg, the FSPE scheme of Canetti et al. and the scheme of Fujisaki and Okamoto, and is proven to be secure based on the hardness of bilinear Diffie-Hellman assumption. At last, we give an identity based (ID-based) version of the proxy cryptosystem based on time segmentation. © Springer-Verlag Berlin Heidelberg 2005.