Improved identity-based signcryption

Identity-based cryptography is form of public-key cryptography that does not require users to pre-compute key pairs and obtain certificates for their public keys. Instead, public keys can be arbitrary identifiers such as email addresses. This means that the corresponding private keys are derived, at any time, by a trusted private key generator. The idea of signcryption is to provide a method to encrypt and sign data together in a way that is more efficient than using an encryption scheme combined with a signature scheme. We present an identity-based signcryption solution that we believe is the most efficient, provably-secure scheme of its type proposed to date. Our scheme admits proofs of security in the random oracle model under the bilinear Diffie-Hellman assumption using the definitions proposed by Boyen.