Reference

  • Towards Black-Box Accountable Authority IBE with Short Ciphertexts and Private Keys.

    (with Benoît Libert) 12th International Conference on Practice and Theory in Public-Key Cryptography, PKC 2009
    (S. Jarecki & G. Tsudik eds.)
    Springer, Lect. Notes Comput. Sci. vol. 5443, 2009, p. 235-255.
top

Abstract

At Crypto'07, Goyal introduced the concept of Accountable Authority Identity-Based Encryption as a convenient tool to reduce the amount of trust in authorities in Identity-Based Encryption. In this model, if the Private Key Generator (PKG) maliciously re-distributes users' decryption keys, it runs the risk of being caught and prosecuted. Goyal proposed two constructions: the first one is efficient but can only trace well-formed decryption keys to their source; the second one allows tracing obfuscated decryption boxes in a model (called weak black-box model) where cheating authorities have no decryption oracle. The latter scheme is unfortunately far less efficient in terms of decryption cost and ciphertext size. In this work, we propose a new construction that combines the efficiency of Goyal's first proposal with a very simple weak black-box tracing mechanism. Our scheme is described in the selective-ID model but readily extends to meet all security properties in the adaptive-ID sense, which is not known to be true for prior black-box schemes.

Keywords

identity-based encryption, traceability, efficiency.

top

Download

[abs]   Abstract
[ps] [pdf]   Proceedings version
top