Abuses in cryptography and how to fight them

Abstract

The following seems quite familiar: '‘Alice and Bob want to flip a coin by telephone. (They have just divorced, live in different countries, want to decide who will have the children during the nezt holiday.)… So they use [Blu82]j’s (OT an improved) protocol. However, Alice and Bob’s divorce has been set up to cover up their spying activities. W h e n they use [BluSZ]’s protocol, they don’t care if the ucoinflip’' is random, but they want to abuse the protocol to send secret information to each other. The counter-espionage service, however, doesn’t know that the divorce and the use o f the [Blu82]’s protocol are just cover-ups. In this paper, we demonstrate how several modern crypto-systems can be abused. We generalize [Sim83b]’s subliminal channel and [DGBS7]’s abuse of the [FFSB7, FS86] identification systems and demonstrate how one can prevent abuses of CTyptOsystems.