A well-known concern in the setting of identity based encryption is that the PKG is all powerful and has to be completely trusted. To mitigate this problem, the notion of Accountable Authority Identity-Based Encryption (A-IBE) was recently introduced by Goyal. Goyal provided constructions to realize the notion of A-IBE only in the white box and weak black box models. However, the security guarantees provided by these models fall short of those required in practice. In this paper, we resolve the main open question left in Goyal's work by providing a construction of a (fully) black box A-IBE system. Our construction is based on the De-cisional Bilinear Diffie-Hellman assumption and uses techniques from key policy attribute based encryption.
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