The first article is just a claim with no evidence provided.

The second is based on some yet unreleased documents that Der Spiegel claims to have reviewed years ago.

Still no evidence to be found, only claims.

It's a claim made by the head of the agency that did it. If you're not willing to take their word, I think you're being stubborn and obtuse and this will never be a productive discussion.

If you're willing to believe a US whistleblower -- whose evidence you can't personally verify -- you have to be open to believing the _former head of the agency_.