Binding ElGamal: A Fraud-Detectable Alternative to Key-Escrow Proposals

We propose a concept for a worldwide information security infrastructure that protects law-abiding citizens, but not criminals, even if the latter use it fraudulently (i.e. when not complying with the agreed rules). It can be seen as a middle course between the inflexible but fraud-resistant KMI-proposal [8] and the flexible but non-fraud-resistant concept used in TIS-CKE [2]. Our concept consists of adding binding data to the latter concept, which will not prevent fraud by criminals but makes it at least detectable by third parties without the need of any secret information. In [19], we depict a worldwide framework in which this concept could present a security tool that is flexible enough to be incorporated in any national cryptography policy, on both the domestic and foreign use of cryptography. Here, we present a construction for binding data for ElGamal type public key encryption schemes. As a side result we show that a particular simplification in a multiuser version of ElGamal does not affect its security.