Translucent cryptography -- an alternative to key escrow, and its implementation via fractional oblivious transfer (Q1291806)

The notion of translucent cryptography represents an interesting alternative to the controversial ``key-escrow'' technique, as it offers the possibility to achieve an appropriate balance between individual privacy and requirements for enabling law enforcement and national security access to encrypted communications. The main feature of the new approach is that it allows to choose a probability \(p\) with which a particular message can be decrypted by the government. In the paper first the main idea of translucent cryptography is explained and then the notion of oblivious transfer is reviewed. However, most of known protocols for oblivious transfer are interactive, while for the intended use to implement translucent cryptography oblivious transfer needs to be noninteractive. For that reason simple non-interactive oblivious transfer protocol by \textit{M. Bellare} and \textit{S. Micali} [Advances in Cryptology -- CRYPTO '89, Proc. Conf., Santa Barbara/CA (USA) 1989, Lect. Notes Comput. Sci. 435, 547-557 (1990; Zbl 0722.68041)] is presented, followed by a description on how such a protocol can be used to implement the main idea of translucent cryptography. However the original protocol provides oblivious transfer for fixed value of \(p = 0.5\) only, thus in the next section it is shown how to achieve noninteractive fractional oblivious transfer for a variety of values for \(p\). Finally variations of the approach are discussed and brief comparison with key escrow is given.