Hierarchical ID-based Encryption with Minimized Key Escrow

Abstract

Identity-based cryptography is a public key cryptosystem in which any arbitrary string such as identity, email address of user can be used as a public key and the corresponding private key is generated by a private key generator (PKG) and given to the user through a secure channel[1][2]. It has advantage in key distribution, but also has drawback of key escrow that PKG knows user’s private key. If multiple PKGs with independent certification domain are used and users belong to different PKGs, it was considered that expanding certification using only ID-based cryptography is difficult between two users who belong to different PKG domains. Gentry and Silverberg[3] presented a hierarchical identity based cryptography which successfully expands certification among multiple PKGs structured in hierarchical manner, thus lots of extended researches followed from it [4-10]. But this scheme has a drawback that all ancestor PKGs of a user can decrypt any message sent to the user even though they do not have the private key of the user, which is very undesirable feature. In this paper we modify Gentry and Silverberg’s hierarchical identity based encryption (HIBE) scheme and present a new HIBE scheme which minimize the key escrow property 접수일(2015년10월27일), 심사의뢰일(2015년10월28일), 심사완료일(1차:2015년11월02일, 2차:2015년11월28일) 게재확정일(2015년12월07일), 게재일(2015년12월31일) 312-702 충청남도 금산군 추부면 마전리 중부대학교 정보보호학과. email: sultan@jbm.ac.kr 키에스크로를 최소화한 계층적 아이디기반 암호 Copyright c 2015 SERSC 546 that only user and the end PKG who issued private key to the user can decrypt message.