Study On Multipurpose Identity-Based Signcryption

The proliferation of computers and communications systems in the 1970s brought with it a demand from the private sector for means to protect information in digital form and to provide security. In order to greatly reduces the problems with key management that have hampered the mass uptake of public key cryptography on a per individual basis, identity-based cryptography has been proposed in 1984 by Shamir. And nowadays the two fundamental services of public key cryptography are encryption and signing. Encryption provides confidentiality as only the intended recipient can recover the plaintext from the ciphertext. Digital signatures provide authentication and non-repudiation. Signcryption is a public key primitive to achieve the combined functionality of digital signature and encryption in an efficient manner.This essay mainly focuses on identity-based signscyption schemes, especially those achieving various security requirements. Firstly, a detailed introduction of identity-based systems and signcryption is given, followed by a brief review of the developmental history in this field. Secondly, some mathematical basis as well as the basis for public-key cryptography are reviewed, including the security notions (for both encryption and digital signature), the random oracle model and several complex assumptions. Then various security definitions for identity-based signcryption schemes are summarized under a particular framework. Finally, a new efficient identity-based signcryption scheme is proposed with security proofs. The new scheme compares favourably with other provably secure signcryption schemes mentioned in the literature in terms of efficiency and security requirement.