GCHQ, NCSC call for end-to-end encryption back door

Dr. Ian Levy, technical director of the National Cyber Security Centre (NCSC) arm of the Government Communications Headquarters (GCHQ) intelligence agency, has outlined a proposal to intercept and decode end-to-end encrypted communications on services like WhatsApp, using what he describes as 'virtual crocodile clips'.

That the government's security services aren't too fond of strong encryption is no surprise: Home Secretary Amber Rudd has previously called for a ban on end-to-end encryption, where the data is encrypted in such a way that it cannot be decrypted or otherwise monitored by any device in the chain apart from the sending device and its intended recipient, further claiming that 'real people' don't care about encryption. The UK, along with its fellow members of the Five Eyes intelligence group, has long called for physically-impossible secure back doors which would allow governments and security services access to encrypted communications while somehow keeping others out.

Now, the Government Communications Headquarters' Dr. Ian Levy, technical director of the National Cyber Security Centre (NCSC), has published a piece written in partnership with Crispin Robinson for the Lawfare Blog calling for 'virtual crocodile clips' that would allow his organisation, and others, to spy on end-to-end-encrypted communications on services like WhatsApp by inserting the government as a hidden third party in the encryption system.

'For over 100 years, the basic concept of voice intercept hasn’t changed much: crocodile clips on telephone lines. Sure, it’s evolved from real crocodile clips in early systems through to virtual crocodile clips in today’s digital exchanges that copy the call data. But the basic concept has remained the same,' Dr. Levy writes. 'Many of the early digital exchanges enacted lawful intercept through the use of conference calling functionality.

'In a world of encrypted services, a potential solution could be to go back a few decades. It’s relatively easy for a service provider to silently add a law enforcement participant to a group chat or call. The service provider usually controls the identity system and so really decides who’s who and which devices are involved - they’re usually involved in introducing the parties to a chat or call. You end up with everything still being end-to-end encrypted, but there’s an extra "end" on this particular communication. This sort of solution seems to be no more intrusive than the virtual crocodile clips that our democratically elected representatives and judiciary authorise today in traditional voice intercept solutions and certainly doesn’t give any government power they shouldn’t have.'

Dr. Levy suggests, entirely disingenuously, that placing a hidden third party, over which the sender and recipient can exert no control, should not be a concern. 'We’re not talking about weakening encryption or defeating the end-to-end nature of the service,' he continues. 'In a solution like this, we’re normally talking about suppressing a notification on a target’s device, and only on the device of the target and possibly those they communicate with. That’s a very different proposition to discuss and you don’t even have to touch the encryption.'

Dr. Levy's proposals, which would require encrypted messaging services to remove protections against exactly this kind of attack - typically taking the form of key verification systems and pop-up alerts when there are additional recipients on a message or additional client devices logged into the same account - have, naturally, been derided by privacy campaigners. Noted whistle-blower Edward Snowden took to Twitter to castigate the proposals: 'Absolute madness: The British government wants companies to poison their customers' private conversations by secretly adding the government as a third party,' he wrote, 'meaning anyone on your friend list would become "your friend plus a spy." No company-mediated identity could be trusted.'

The full post, Principles for a More Informed Exceptional Access Debate, is available on the Lawfare Blog.