Cryptology ePrint Archive: Report 2005/015

Hierarchical Identity Based Encryption with Constant Size Ciphertext

Dan Boneh and Xavier Boyen and Eu-Jin Goh

Abstract: We present a Hierarchical Identity Based Encryption (HIBE) system where the ciphertext consists of just three group elements and decryption requires only two bilinear map computations, independent of the hierarchy depth. Encryption is as efficient as in other HIBE systems. We prove that the scheme is selective-ID secure in the standard model and fully secure in the random oracle model. Our system has a number of applications: it gives very efficient forward secure public key and identity based cryptosystems (where ciph ertexts are short), it converts the NNL broadcast encryption system into an efficient public key broadcast system, and it provides an efficient mechanism for encrypting to the future. The system also supports limited delegation where users can be given restricted private keys that only allow delegation to certain descendants. Sublinear size private keys can also be achieved at the expense of some ciphertext expansion.

Category / Keywords: public-key cryptography / Identity Based Encryption

Publication Info: Full version. Proceedings version at

Date: received 20 Jan 2005, last revised 25 Jan 2006

Contact author: eujin at cs stanford edu

Available format(s): Postscript (PS) | Compressed Postscript (PS.GZ) | PDF | BibTeX Citation

Version: 20060126:050712 (All versions of this report)

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