One of the most significant milestones in cryptanalysis was the development by Alan Turing and others (see Advent calendar item for 9th of December) of electro-mechanical devices to help break the German Enigma cipher in World War Two.
Turing (left) joined the National Physical Laboratory (NPL) after the war and designed his revolutionary electronic computing machine – the Automatic Computing Engine (‘ACE’). Donald Davies (right), who was briefly Turing’s assistant at NPL, co-invented the concept of packet-switching, the basis of most computer data communications.

Today, NPL is helping to test new encryption technology that will keep our data communications secure, so that no future machine will ever be able to break it. Data is one of the world’s most valuable commodities – impacting every individual, organisation, and government. Most cybersecurity infrastructure is based on the exchange and use of digital keys. This has been very effective so far; however, advances in quantum computing have dramatically raised the threat to this infrastructure.

The solution is a combination of algorithmic encryption, aimed to be secure against a quantum computer, and quantum key distribution (QKD). QKD distributes secret digital keys using optical communication at the single-photon level. Uniquely, it provides protocols whose security can be proven by the laws of nature, rather than relying on computational complexity, and does not require assumptions about an adversary’s resources. However, differences between a real QKD system and its mathematical model could introduce vulnerabilities.

In OPENQKD, NPL will quantify these differences and the effectiveness of measures to counter vulnerabilities in order to evaluate the security of the QKD keys.