Attack on an Identity-Based Signcryption Scheme

摘要

Recently, Yu et al.[14] have propose an identity based signcryption scheme, and claimed that their scheme is semantically secure against chosen ciphertext attacks and existentially unforgeable against chosen message attacks without random oracles. However, in this paper, by presenting concrete attacks, we show that their scheme is neither semantically secure nor existentially unforgeable in their security model.