Verified cryptography for Firefox 57

The Mozilla Security Blog announcesthat Firefox 57 will benefit from the addition of a formally verifiedcrypto package."The first result of this collaboration, an implementation of theCurve25519 key establishment algorithm (RFC7748), has just landed inFirefox Nightly. Curve25519 is widely used for key-exchange in TLS, and wasrecently standardized by the IETF. As an additional bonus, besides beingformally verified, the HACL* Curve25519 implementation is also almost 20%faster on 64 bit platforms than the existing NSS implementation (19500scalar multiplications per second instead of 15100) which represents animprovement in both security and performance to our users."