Lazy reporting: "The U.S. officials said they are certain U.S. spy agencies themselves aren't behind the back door."
If you're not going to provide context or get a quote from a disinterested party, then just omit the US saying the US didn't do it.
If you're not going to provide context or get a quote from a disinterested party, then just omit the US saying the US didn't do it.
This feels incredibly uncomfortable to say but in a decade or two it seem possible or maybe even likely that China, Russia and South Korea may have an edge in encryption technology and products by virtue of them actually being secure. I mean if they take cyberwar seriously, and think their economy has anything to do with national security, they'll pour energy into securing their businesses whereas the west does the opposite.