Encryption is one of the words that make most readers hurriedly turn the page. Yet if you ever use a plastic payment card, you benefit from it. If you ever let your personal details be stored on someone else’s database, you rely on it. If you ever use a password on your computer, you use it. Contrary to the home secretary’s assertion this week that strong encryption is not a priority for “real people”, these are applications that real people depend on.
Most people, perhaps even Amber Rudd, do not understand the maths behind encryption. But its effects are simple enough. The internet, a deeply insecure computer network, has become the central nervous system of modern civilisation. Encryption gives us the best chance of protecting it from criminals, spies, pranksters and other enemies.
Used properly, encryption allows us to identify ourselves securely on the internet. It allows us to check who we are dealing with and exchange information with them privately. Without encryption we might as well conduct all our business by postcard.
We actually need more encryption, not less. The wave of cybercrime sloshing across Britain largely results from our failure to make messaging secure: for example, it allows criminals to use fake emails to impersonate the parties in a property transaction, diverting life-ruining sums of money from buyers and sellers. The mandatory use of encrypted authenticated email, or even WhatsApp, would stop that fraud at a stroke.
What bothers Ms Rudd, and others in the police and counterterrorism world, is the uncrackability of modern encryption. The perpetrator of the Westminster attack in March, Khalid Masood, connected to WhatsApp two minutes before he started killing people. Any message he sent or received would presumably be an important clue. The authorities have the right, with a warrant, to search his house; why should they not have a similar ability to search his phone?
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The reason is because it would weaken security for everyone else. If we mandate tech companies to store the keys to every encryption service they use, and to provide them to the authorities when needed, we create a series of grave weaknesses and dilemmas. Would a court order from the British authorities carry the same weight as one from Turkey? Or Russia? Or China? At the moment, the internet companies can quite truthfully say that they cannot provide keys that they do not hold: on WhatsApp and similar services, only the users themselves have access to the content of the messages.
“Spy agencies can lurk invisibly on almost any phone anyway
To be fair to Ms Rudd, she is not suggesting that the providers create back doors, which would be dangerously attractive targets for criminals, spies, pranksters and other adversaries. Last year some of the CIA’s most closely guarded hacking tools were stolen by the so-called Shadow Brokers. Hackers have breached companies such as TalkTalk and Yahoo and stolen customer passwords and login details. Imagine how much more dangerous the loss of the keys that guard the secure communications of hundreds of millions of people would be. We already allow far too much of our personal data to be held by third parties, with far too little scrutiny or security. We should not add our private encryption keys, in effect our crown jewels, to that data swamp.
But users of these services are not fools. If the authorities arm-twist WhatsApp and other western-owned providers of encrypted communications to use weaker encryption, as Ms Rudd suggests, people will find alternatives. Encryption software used to be a closely guarded secret, to the point that it was covered by arms-export rules. Now it is instantly available on the internet. With a few minutes fiddling on my laptop or phone, I can install an encryption system using free, easily downloadable software that would defeat a head-on attack by even the codebreakers of GCHQ.
Yet our spies are far from helpless when it comes to tackling our enemies’ communications. GCHQ is notably absent from the calls for artificial weakening of encryption systems. This is because they understand its importance and already have formidable capabilities to get the information they need by other means. Encryption is like a tunnel: the information may be secure in transit, but to be useful it must still go in at one end and come out at the other.
That involves inherent vulnerabilities. Spy agencies can lurk invisibly on almost any computer or phone, copying every keystroke and reading everything that appears on the screen. Encryption may even be a telltale sign: if you are interested in people who attend a particular mosque known for its inflammatory preaching, those who use super-strength security on their phones are probably the ones you want to target.
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It is true that applying those techniques retrospectively can be hard, as in the case of Khalid Masood’s phone. Yet even then, options exist. The FBI tried to force Apple to create a special key to weaken the encryption on another dead terrorist’s iPhone. The tech giant resisted, citing the risk to other users’ security. The FBI then found a private contractor able to break into the device another way.
The tech companies do deserve a lambasting for their greed and complacency. Ms Rudd is right to urge them to talk seriously to government agencies and to think about what more they can do to foil terrorism. But decrying end-to-end encryption as an irrelevant luxury reveals either ignorance or cynical grandstanding: it is hard to know which is worse.