and maybe not.
This isn't the Enigma that was deciphered after realizing that Heil Hitler was used on every transmission.
How about if we don't blow things out of proportion?
This was released some time back:
Back around 2000, a high-level associate of Osama bin Laden was captured. Over the course of years of interrogation in Cuba, he had nonchalantly mentioned the name of a low-level, unimportant person within al-Qaeda. Ten years later, as US intelligence routinely scanned electronic communications chatter that might or might not be genuine al-Qaeda communications, they heard that name mentioned. In this case, it was in reference to Osama bin Laden's personal driver. Yes, the man who had been unimportant enough to have been nonchalantly revealed ten years earlier had risen in rank over time to become someone consistently by bin Laden's side.
That gave credibility to that particular channel of chatter, both the originator and the receiver, that the Intelligence Community had not had before. Those were people who were truly "in the know" and not just "wannabes." That channel became important as an intelligence source. Moreover, it gave the IC a real grasp of bin Laden's whereabouts and movements...and it wasn't long afterward that bin Laden wound up dead.
How out of proportion was the mere dropping of the name of someone of little importance?
But here is where I think we went wrong: After bin Laden was killed, Obama immediately went public with it. I wouldn't have done that, and I'm sure there was a lot of cringing going on in the IC the night of that announcement. If the US had said nothing--if Obama had kept the matter secret for just a while longer--it would have provided another intelligence bonus as we listened to the chatter in the aftermath. Which channels seemed unaffected? Which ones changed abruptly? Which went silent? That would have given us additional verification of which were actually al-Qaeda and which were wannabes.
In the same way, even the release of a contact list or an email addressee list provides useful information to enemy intelligence agencies even if they can't decrypt the content of the message. Even if the content of the message has been OBE'd (Overcome by Events), it can contain valuable information. That's why many WWII German and Japanese messages decrypted in the 1940s remain classifed even today.