We recognized that the chances of finding an acyclic path were slim indeed. Due to the to the explosive number of paths in an EFT graph, which contains a tremendous number of arcs, stumbling upon such a path within our lifetime was unlikely. Still, as long as the machines were idle anyway, we figured we might as well put them to work (we were desperate).
It was Rudy that came up with the name of deep-throat for the program that enumerates EFT paths. He pointed out that the person code-named Deep-Throat that had helped Woodward and Bernstein expose Watergate had repeatedly told them to “follow the money.” And that is precisely what this program does. With luck, we would be able to follow the money down the millrace and right into the millwright’s bank account. Then we would turn the matter over to the FBI and let them arrest him or her. It would not be easy though. We already had ample evidence that the millwright was a clever computer scientist and expert cryptanalyst. He or she — it was at this point that I decided to myself that I would presume the millwright was a male; it makes it much easier to think and talk. He might have anticipated the investigative approaches we were taking. Clearly he had anticipated a deep-throat style program and had come up with the clever trick of hiding the entire crime within an NP problem. This demonstrated strong expertise in computer science as well as a mind that is capable of devious trickery. The attack itself — counterfeiting EFT messages that rely upon DES MAC’s for authentication — requires highly unusual skill in cryptanalysis. There are very few known weaknesses in the DES algorithm. The few weaknesses that have been published are directly related to key-size and not to the DES algorithm itself. Triple-DES, which makes use of two 56-bit keys and three iterations of the regular DES algorithm, is very strong indeed. The world’s best cryptanalysts have not been able to come close to cracking triple-DES, and it has been in wide-spread use for three decades. If the millwright is able to forge DES MAC’s — and all evidence pointed in this direction — then he was one of the worlds top cryptanalysts. Our task would not be easy. To succeed the three of would need help from deep-throat, BIF, the FBI, and fate.