Identity-based encryption (IBE) is an attractive primitive in modern cryptography. Cocks first gave an elegant construction of IBE under Quadratic Residuosity (QR) assumption. Unfortunately, its security works only in the Random Oracle (RO) model. In this work, we aim at providing Cock’s scheme with provable security in the standard model. Specifically, we modify Cocks’ scheme by explicitly instantiating the hash function using indistinguishability obfuscation in two different ways which yield two variants of Cocks’ scheme. Their security are promised under well-defined selective-ID and adaptive-ID model respectively. As an additional contribution, we adapt the same method into the Boneh, LaVigne, Sabin (BLS) eth residuosity based IBE cryptosystem and obtain an adaptive chosen-ID secure scheme under Modified eth Residuosity (MER) assumption.
CITATION STYLE
Wang, X., Li, S., & Xue, R. (2019). Cocks’ identity-based encryption in the standard model, via obfuscation techniques (short paper). In Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) (Vol. 11689 LNCS, pp. 273–283). Springer Verlag. https://doi.org/10.1007/978-3-030-26834-3_16
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