Direct chosen ciphertext security from identity-based techniques

摘要: We describe a new encryption technique that is secure in the standard model against chosen ciphertext attacks. base our method on two very efficient Identity-Based Encryption (IBE) schemes without random oracles due to Boneh and Boyen, Waters.Unlike previous CCA2-secure cryptosystems use IBE as black box, approach simple compact. It makes direct of underlying structure, requires no cryptographic primitive other than scheme itself. This conveys several advantages. achieve shorter size best known instantiations methods, Katz (and more so Canetti, Halevi, Katz). Further, operates nicely hierarchical IBE, since it allows validity ciphertexts be checked publicly, can used construct systems with non-interactive threshold decryption.In this paper we main constructions: full system based Waters adaptive-ID KEM Boneh-Boyen selective-ID IBE. Both are shown model, latter tight reduction. discuss uses extensions approach, draw comparisons provably model.