NSA and GCHQ
@andyp-random-number
Once you read up on how it works (see the excellent link from Doctor Syntax) it looks very unlikely anyone was involved. The advancement of processors is what brought about this problem which is why multiple processors are in trouble. They didn't really have any other way to progress and the problem is in the implementation.
You couldn't get the designers from multiple companies to all secretly put a back door in all the processors. They won't all have been Americans/English and they won't all have worked in the America/England.
Personally when I look at a potential conspiracy I determine how many people would have to keep quite for it to stay secret, whether they were all the same group (which can be Nationality/government/race/religion/political affiliation/secret group with a funny handshake or ring) and if it's plausible. I don't think there are many that pass this test and even then I'm still extremely sceptical. In fact the only one that is still sat as a conspiracy is JFK because there is too much conflicting information, not a clue which theory is right though though I'm leaning towards professor plum in the kitchen with the hammer.