CurveCP in Go
Interest waned when it became clear djb was unlikely to return to this alpha project soon (read: years/never), while working on other crypto primitives/maths. Nonetheless, I recommend reading the CurveCP protocol as an elegant and beautiful brick in the Computer Science canon. It is quite straighforward, yet neatly cleaves long-painful issues of security, while improving latency (not to mention mobility and other tricks). It will inform many protocols to come, an early progeny being QUIC -- which oddly mentions its progenitor not.