Comments on Shao-Cao's Unidirectional Proxy Re-Encryption Scheme from PKC 2009
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 Can 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.
proxy re-encryption chosen-plaintext attack chosen-ciphertext attack bilinear pairing transformed ciphertext