[math-fun] How a weak NIST backdoors Diffie-Hellman

FYI -- www.ams.org/notices/201402/rnoti-p190.pdf "The NSA Back Door to NIST" "We give a brief mathematical description of the NIST standard for cryptographically secure pseudo- random number generation by elliptic curves, the back door algorithm discovered by Ferguson and Shumow, and finally the design of the back door based on the Diffie-Hellman key exchange algorithm."