Direct Chosen-Ciphertext Secure Identity-Based Key Encapsulation Without Random Oracles

We describe a new and practical identity-based key encapsulation mechanism that is secure in the standard model against chosen-ciphertext (CCA2) attacks. Since our construction is direct and not based on hierarchical identity-based encryption, it is more efficient than all previously proposed schemes. Furthermore, we give the first chosen-ciphertext secure identity-based key encapsulation mechanism with threshold key delegation and decryption in the standard model. 1 CWI Amsterdam, The Netherlands. Email: [email protected]. URL: http://kiltz.net. 2 Institute for Computing and Information Sciences, Radboud University Nijmegen, The Netherlands. Email: [email protected]. URL: http://www.cs.ru.nl/~dgalindo/.