Client-Side Scanning is not a silver bullet

This morning’s Observer column:

In August, Apple opened a chink in the industry’s armour, announcing that it would be adding new features to its iOS operating system that were designed to combat child sexual exploitation and the distribution of abuse imagery. The most controversial measure scans photos on an iPhone, compares them with a database of known child sexual abuse material (CSAM) and notifies Apple if a match is found. The technology is known as client-side scanning or CSS.

Powerful forces in government and the tech industry are now lobbying hard for CSS to become mandatory on all smartphones. Their argument is that instead of weakening encryption or providing law enforcement with backdoor keys, CSS would enable on-device analysis of data in the clear (ie before it becomes encrypted by an app such as WhatsApp or iMessage). If targeted information were detected, its existence and, potentially, its source would be revealed to the agencies; otherwise, little or no information would leave the client device.

CSS evangelists claim that it’s a win-win proposition: providing a solution to the encryption v public safety debate by offering privacy (unimpeded end-to-end encryption) and the ability to successfully investigate serious crime. What’s not to like?

Plenty, says an academic paper by some of the world’s leading computer security experts published last week…

Read on