Provably secure proxy-protected signature schemes based on RSA

The proxy signature schemes allow proxy signers to sign messages on behalf of an original signer, a company or an organization. Such schemes have been suggested for use in a number of applications, particularly in distributed computing, where delegation of rights is quite common. Most of proxy signature schemes previously proposed in literatures are based on discrete logarithms or from pairings. In 2003, Shao proposed the first two proxy signature schemes based on RSA. Though being very efficient, they have no formal security proofs. In this paper, we provide formal security proofs under a strong security model in the random oracle model after minor modification.