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MIN-RONG CHEN1,2, XI ZHANG3,+ AND XIA LI2
1Management School
Jinan University
Guangzhou, 510632 P. R. China
2College of Information Engineering
3College of Computer and Software
Shenzhen University
Shenzhen, 518060 P.R. China
Proxy re-encryption (PRE), introduced by Blaze, Bleumer and Strauss, allows a semirusted
proxy to convert a ciphertext originally intended for Alice into an encryption of
the same message intended for Bob. In PKC'09, Shao and Cao proposed a unidirectional
PRE scheme without pairings, and compared their scheme with Libert-Vergnaud's pairing-
based unidirectional PRE scheme from PKC¡¦08. In this paper, we indicated that
Shao-Cao's scheme is not secure against chosen-plaintext attack in Libert-Vergnaud's
security model.
Received October 1, 2009; revised January 22, 2010; accepted March 26, 2010.
Communicated by Wen-Guey Tzeng.
* This work is supported by the National Natural Science Foundation of China under Grants No. 61005049 and
60772148, and the Specialized Research Fund for Ph.D. Program Foundation of Colleges and Universities of
China under Grant No. 200805900001.
+ Corresponding author.