Identity-based encryption

ID Based Cryptography is a public key cryptographic system in which the public key is some unique information about the identity of a user (e.g. email address).

This system works by having a trusted third party who has a secret which can be combined with a user's identity information to produce the user's secret key. The third party also produces some public information which is derived from its secret.

When signing or decrypting the system is essentially the same as conventional private key cryptography, however to perform signature verification and to sign a message the user uses their private key, but to verify the signature or encrypt a message only the identity information and the third partiy's public information is needed.

Originally when this system was first developed in 1984 by Adi Shamir it could only be used for keys for digital signatures, however recently this method has been extended to cryptography.

Only limited work has been done in terms of formally analysing ID based cryptosystems, some of which have been recently broken.

References

• Adi Shamir. Identity-Based Cryptosystems and Signature Schemes. Advances in Cryptology: Proceedings of CRYPTO 84, Lecture Notes in Computer Science, 7:47--53, 1984.
• Yevgeniy Dodis, Jonathan Katz, Shouhuai Xu, Moti Yung, Strong Key-Insulated Signature Schemes (2002).