Militaries have been trying to keep their communications safe from prying eyes for centuries. But they have also sought to be able to communicate as quickly as possible and as widely as possible with their own forces. Those requirements are in tension with one another.

Today, militaries can communicate globally over increasingly capacious data pipes. But the same technological evolution that allows them to do that has also given would-be eavesdroppers new and powerful tools to collect and exploit signals.

In this report, author Dr Andrew Davies explains the principles of secure communication and uses some examples of emerging technologies to illustrate what the next generation of secure communications might look like.