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. © International Association for Cryptologic Research 2009.
CITATION STYLE
Libert, B., & Vergnaud, D. (2009). Towards black-box lack-box accountable authority ibe with Short ciphertexts and private keys. In Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) (Vol. 5443, pp. 235–255). Springer Verlag. https://doi.org/10.1007/978-3-642-00468-1_14
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