Notes on Proxy Signcryption and Multi-proxy Signature Schemes

Proxy signcrytipn scheme allows an original signer to delegate his signing power to a proxy such that the latter can signcrypt a message on behalf of the former. Recently, Lin et al. proposed a proxy signcryption with CCA and CMA security. In this work, we indicate that the Lin et al.’s proxy signcryption scheme does not hold the security of indistinguishability against adaptive chosen-ciphertext attacks and existential unforgeability against adaptive chosen-message attacks. Also, we show that the Jin-Wen’s certificateless multi-proxy signature scheme does not hold the security of existential unforgeability against adaptive chosen-message attacks.