“I too approached Lisa Cryer with an offer to trade information,” I said. “She suggested that I meet with you because you and I both have information to trade.” I was reluctant to say more. It is one thing to admit illegal activity to a private citizen such as Lisa and quite another to confess to a bank investigator.
“I see,” Levinski said softly. He now turned and faced me squarely. He appeared to study me for the first time now. He asked who I worked for. When I explained my employment situation, it seemed to please him and put him at ease. He unclasped his hands and put one in his pocket. He wiped his forehead with the other. We then danced around the matter of trading information, both of us reluctant to divulge even the nature of our secrets without first receiving at least an inkling of the other’s secrets.
I wondered what he knew about the inner machinations of his bank. From the beginning the behavior of First Chicago had been suspicious to me. I recalled the strange reactions of First Chicago executives in the phone conversations I had tapped. How could they seriously have suspected Lisa Cryer of wrong-doing when it was First Chicago that rejected all of the messages in the first place?
It became clear that whatever information Rudy Levinski had — information that he was unwilling to give to the FBI — was not going to be forthcoming until I told him more about myself. But I sure as hell wasn’t going to tell him that I had conducted illegal wire-taps and impersonated a US bank. I tried a different approach.
“Lisa denies two of the EFT’s that were processed by your bank on July 12th,” I told him. “And I believe her. The trouble is, the MAC’s for the false EFT’s appear to have checked out OK. Can you confirm that?”
“Yes. I know of the two EFT’s to which you refer. The MAC’s were proper. They were calculated using the same cryptographic key as all of the other MAC’s in that batch. Either the subject knew the key or he was able to create a perfect forgery. I assure that the latter is extremely unlikely. There are no known feasible attacks on the encryption used.”
This I knew, of course. DES is a strong encryption algorithm. It is somewhat dated at this point, but provided one uses long keys it remains strong to this day. It is arguably the best symmetric-key algorithm today. It has withstood three decades of intense cryptanalysis.
Rudy seemed to be opening up a bit. He still looked tense and nervous, but his last answer had been somewhat informative. He would not have known my background in cryptology and was probably making a legitemate effort to cooperate. I tried asking another question.
“Every EFT in the original transmission from Bendix was rejected by First Chicago. What was the reason for that?”
Mr. Levinski raised a hand between us and smiled gently. “I answered your question. Now it is my turn to ask you a question. How did you know that the illegal EFT’s were included in the same transmission as the others?” Then, after a slight pause he added, “and how did you know that First Chicago rejected each and every EFT in the original transmission?”
“That is two questions,” I pointed out, “but since the same answer covers both, I’ll answer them both. I was eavesdropping on the transmission between Bendix and First Chicago on July 11th. I did not alter the transmissions at all,” I added hastily. “I observed the traffic but let all messages pass back and forth unobstructed and unaltered.”
He nodded his head slowly and showed no surprise. I was suddenly very anxious to absolve myself.
“I had no malicious intent. I am a security professional and was merely observing the traffic to determine the protocol used for funds transfer. The published standards are vague about error-handling. In fact, I was pleased to see the error messages from First Chicago because they were instances of error messages that I wanted to see.”
I realized then that he might think that my interest in error messages drove me to take steps to cause errors (which is true) and that I intentionally garbled the messages from St. Louis to Chicago (which is untrue). I hastened to reassure him.