You are understating the level of evidence that points to the NSA being fully aware of what it was doing.
To be clear, the method of attack was something that had been described in a paper years earlier, the NSA literally had a program (BULLRUN) around compromising and attacking encryption, and there were security researchers at NIST and other places that raised concerns even before it was implemented as a standard. Oh, and the NSA paid the RSA $10 million to implement it.
Heck, even the chairman of the RSA implies they got used by the NSA:
In an impassioned speech, Coveillo said RSA, like many in industry, has worked with the NSA on projects. But in the case of the NSA-developed algorithm which he didn’t directly name, Coviello told conference attendees that RSA feels NSA exploited its position of trust. In its job, NSA plays two roles, he pointed out. In the information assurance directorate (IAD) arm of NSA, it decides on security technologies that might find use in the government, especially the military. The other side of the NSA is tasked with vacuuming up data for cyber-espionage purposes and now is prepared to take an offensive role in cyber-attacks and cyberwar.
“We can’t be sure which part of the NSA we’re working with,” said Coviello with a tone of anguish. He implied that if the NSA induced RSA to include a secret backdoor in any RSA product, it happened without RSA’s consent or awareness.
What type of confirmation do you want? The documents aren't going to be declassified in the next couple of decades, if ever.
I've never heard anyone claim that Dual_EC_DRBG is most likely not intentionally backdoored, but there's literally no way to confirm because of how its written. If we can't analyze intention from the code, we can look at the broader context for clues. The NSA spent an unusual amount of effort trying to push forward an algorithm that kept getting shot down because it was slower than similar algorithms with no additional benefits (the $10 million deal specified it as a requirement [1]). If you give the NSA the benefit of the doubt, they spent a lot of time and money to... intentionally slow down random number generation?!
As an American, I'd prefer a competent NSA than an incompetent NSA that spends my tax dollars to make technology worse for literally no benefit...
