University of California
"Identity-based public key encryption facilitates easy introduction of public key cryptography by allowing an entity's public key to be derived from an arbitrary identification value, such as name or email address. The main practical benefit of identity-based cryptography is in greatly reducing the need for, and reliance on, public key certificates. Although some interesting identity-based techniques have been developed in the past, none are compatible with popular public key encryption algorithms. This limits the utility of identity-based cryptography as a transitional step to full-blown public key cryptography."