Date Added: Aug 2012
Confidentiality and authenticity are two fundamental security requirement of Public key Cryptography. These are achieved by encryption scheme and digital signatures respectively. Here the authors present a provably secure signcryption scheme in random oracle model by modifying Libert et al's scheme. Their scheme is more efficient and secure than Libert et al's scheme. Tan proved that this scheme is not secure against non-adaptive chosen cipher text attacks. It has been also proved that the semantically secure symmetric encryption scheme proposed in the Libert et al's scheme is not sufficient to guarantee to be secure against adaptive chosen ciphertext attacks. Here they proposed a modified version of Libert et al's scheme.