“The program Lisa mentioned is a start,” I said. “However, as Lisa said, it is a long-shot. An NP-complete problem is a computer problem for which there are no known efficient solutions. Tracing money throughout the EFT network happens to be an example of such a problem. If the money we are tracing is divided into several seperate transactions before it is moved to the next account, and then if each of those transactions is divided still further before being routed to the accounts after that, then the number of paths that we must trace increases dramatically in very short order. If the millwright divides transactions into ten parts each step of the way, then after tracking the money through four such divisions, we are up to ten thousand paths. It is even worse than that because the forgeries are indistinguishable from the real EFT traffic. It is like following a gallon of water as it flows down a river, where the river splits, joins other rivers, reunites, splits again, and so on. Like the gallon of water, bogus EFT’s are indistinguishable from real EFT’s. Like the gallon of water, the money of the original EFT is seperated, with a few pennies going here and few pennies going there.”
“But then how can the hacker keep it all straight?” asked Agnes, letting her exasperation show as she threw her hands in the air.
“I don’t know,” I replied. “He must be using a computer to orchestrate the whole thing. The decoy paths are generated by a program. I am certain of it. It is easy to write a program to generate an NP problem — solving one is the tricky part.”
Templemeyer’s face turned pale. “Are you telling me that this is unstoppable? Is that what you two Computer Scientists are saying? Is there no way to track down the counterfiet money?”
“Not that I can see.”
“I… I don’t think anybody at the ABA anticipated an attack which uses computers to such a degree. Hundreds, no thousands of forged transfers ocurring daily! Most of them mere decoys to obscure a small number of profitable counterfeits… and even those are laundered through many different accounts…
“How long has this been going on?” he asked imploringly.
“I don’t know,” I replied curtly. I feared that it had been going on for a long time. Why not? It was the perfect crime. We would still be ignorant of the entire matter if not for the triple coincidence of my replays, the delay scam, and the mill. It was the interference pattern of these three seperate attacks that lead to the detection of all three. Without the other two, any one of these attacks would have gone undetected. This is especially true for the money mill, for it was disguised in a truelly ingenious manner.
“For all we know the mill has been running for years,” I said. This news brought out muttered curses from everybody in the room. Templemeyer was near panic. He turned to Agnes.
“What do we do?”
Agnes refused to be rattled. Her reply was calm and her thinking clear. “If Carl is right and this criminal activity has been taking place of a long time — maybe even years — then there is no immediate threat. We have survived thus far while the mill is in full swing; we can survive a while longer. If computer-aided investigation won’t work then we must try more conventional forensics. This we are already doing. I will have Mr. Levinski brought in for questioning. Clearly he has a great deal of information to share with us. Carl, I want you and Lisa to sit down with Agent Carter and give him a full briefing. I was told that you have a second computer program that is also supposed to help with the investigation; be sure to give Agent Carter a full explanation of both programs. He is an expert in computers.”
She leaned over her desk and looked around the room at her make-shift team. One FBI agent, one scared banker, and two computer geeks. If she was dissappointed with what she saw she did not let it show. Her clenched fists pressed against her desk-top as she used her straightened arms to support herself.
“I want to get to the bottom of this… now! Let’s move quickly on this. Templemeyer, I’m going to take this matter up with Samuelson and I want you in attendance.”
Templemeyer nodded and wet his lips. He still had not recovered from his shock over the gravity of the situation. Agnes slammed a fist on her desk. She turned to me as she continued to issue instructions.