the other freaky thing about the communist smear of McCarthy was that they assumed McCarthy senate hearings were a set up in the same way that the Russian show trials were a set up for mass murder.
This was not the case. Nor was it ever in the cards.
What was the case was that at the time Stalin was gearing up for a pogrom in what was later to be known as the "Doctor's Plot". The historical evidence suggests that this would have happened had not Stalin died.
As it is the number of Spies that McCarthy talked about fairly well matched the number of spies that the Venona cables outed and intimated. (I think the confirmed spies were something like 100 and the number of spies that the cables pointed to--but couldn't name--was something like 400.)
The national security agency told the FBI about the information contained on the Venonoa cables but insisted that the FBI had to develop their own information to make the cases against the spies. They couldn't use NSA info to convict them. In most of the cases the FBI was unable to do so. People like the Rosenburgs and the Hiss's were the exception.
Did the FBI tell McCarthy about the Venona intercepts? There is no evidence that this happened. But the coincidences seem strong enough to suggest that time may eventually tell a bit more about that angle.
The really grisly part of this story is that the Russian KGB had a spy in the NSA decoding department who told the Russians that their diplomatic code had been broken in 1948. So the Russians knew. And the Americans learned about the spy soon after. (he fled the country first.)
That means that both Russian and American intelligence knew about the facts behind Venona and McCarthy and they knew that each other knew.
It was the US public that was left in the dark. And this has been the cause of unbelievably bitter divisions in the country since.
I'm not aware of any spy that was aware of Venona. The venona intercepts were made possible because the Soviets couldn't get new one-time pads to their far-flung stations. So the stations re-used one time pads. The technical fact is that a random one-time pad is mathematically provable as unbreakable -- at a depth of one. If you reuse a one-time pad, as the Soviets had to, it becomes a VERY possible thing to break it.
Most of the Venona intercepts were espionage traffic (KGB). That's why it gives such a great insight into the McCarthy era spies, most of whom were recruited in the thirties when the USSR seemed like the New Deal taken to its logical conclusion. Only the true believers among them still worked for the Soviets after the show trials (meaning, ALL of them betrayed us during the World War).
Just because breaking a one-time pad at a depth of two is possible. is not the same thing as saying it is trivial. In the raw breaks, once available on NSA's website, there are a lot of incomplete messages and uncertain areas. And... while we have (or had) the entire Venona intercepts, the counterspies of the forties and fifties didn't. The Venona intercepts are a body of work that was building until (IIRC) 1981, and even the low-hanging fruit were just coming exploitable in the McCarthy era (at least, if you discount the fact that GCHQ was working on them when it was still Bletchley Park. Nothing from that period has been or will be declassified).
The NSA spies I'm aware of, except for Pelton and Pollard, were low-echelon guys who were working in the military, collecting end of the agency. All Venona related stuff took place, as far as I can tell, at HQ.
d.o.l.
Criminal Number 18F