Signcryption

In cryptography, signcryption is a public-key primitive that provides the properties of both digital signatures and encryption schemes, in a way that is more efficient than signing and encrypting separately. This means that at least some aspect of its efficiency (for example the computation time) is better than any hybrid of digital signature and encryption schemes, under a particular model of security. Note that some times hybrid encryption can be employed instead of simple encryption, and its session-key reused, to achieve better overall efficiency across many signature-encryptions; but, the session-key reuse causes the system to loose security under even the relatively weak CPA model. But a signcryption scheme would be more efficient than a simple signature-hybrid encryption combination.

Signcryption was introduced by Yuliang Zheng in 1997 [Y. Zheng, Digital Signcryption or How to Achieve Cost(Signature & Encryption) << Cost(Signature) + Cost(Encryption), Advances in Cryptology -- Crypto'97, Lecture Notes in Computer Science, Vol. 1294, pp. 165-179, Springer-Verlag, 1997.] . A formal proof of security was not established till a later paper did. Now there are several variations and enhancements of signcryption available, many with formal proofs of security established.

Applications

Signcryption is seen to have several applications including the following:
* Secure and authentic email
* E-commerce applications that often require confidentiality, authenticity (by unforgeability), and possibly non-repudiation.

References

Offsite links

* [http://www.signcryption.net/ Signcryption Central]