I think it has to do with public key cryptography - in particular, elliptic curve cryptography[0], which was mentioned by Schneider to be one of the key topics on NSA's agenda[1].

[0] https://arstechnica.com/security/2013/10/a-relatively-easy-t... [1] https://www.schneier.com/blog/archives/2015/10/why_is_the_ns...