Optical cryptography

A better way to process encrypted data

Fully homomorphic encryption is easy if you do it with light

THE DIGITISATION of modern life means data security is ever more important. Data in storage and transit are normally encrypted, and therefore safe from prying eyes. But for computation to happen, they usually have to be unencrypted first. This is a particular problem with so-called cloud computing (in reality, just row upon row of stacks of computers in server farms), which happens beyond a data-owner’s control. And it is getting worse, as more and more devices refer calculations back to various clouds, rather than doing them locally.

A possible answer is a technique called fully homomorphic encryption (FHE). This permits computation directly on encrypted data. Someone with the correct key could, using FHE, send information to a cloud, have it processed there, and get the results back without putting anything sensitive at risk.

The difficulty with this approach is that it is slow. Very slow. Nick New, boss of Optalysys, a small firm in Britain, says a computation that takes a second on unencrypted data…