What end-to-end encryption actually protects and what it does not

When WhatsApp tells its two billion users that "no one outside of this chat" can read their messages, the claim is narrower than it sounds. End-to-end encryption means the message is scrambled on the sender's phone and unscrambled only on the recipient's, so the company carrying it, the network operator, and anyone tapping the wire in between see ciphertext. That part of the promise holds. The Signal protocol, which underpins WhatsApp, Signal itself and Google Messages, has survived years of academic scrutiny, and there is no public evidence that GCHQ or anyone else can break it in transit.

What the promise does not cover is everything either side of the pipe. The phones at each end hold the messages in readable form, because they must, or you could not read them yourself. A screenshot, a stolen unlocked handset, a piece of spyware such as NSO Group's Pegasus, or simply the other participant showing the conversation to someone else all defeat encryption without touching it. Under section 49 of the Regulation of Investigatory Powers Act 2000, refusing to hand over a PIN or password when properly ordered is itself a criminal offence carrying up to two years in prison, five in national security cases. British police rarely need to attack mathematics when they can attack the device or its owner.

Metadata is the second exclusion, and arguably the more consequential one. WhatsApp cannot read your messages, but it knows which numbers you contacted, at what times, from which IP addresses, and how large each message was. Under the Investigatory Powers Act 2016, communications data of this kind can be acquired by police forces with internal authorisation routed through the Office for Communications Data Authorisations, a far lower bar than the double-lock warrant needed for content. A former NSA director's remark that "we kill people based on metadata" was flippant, but the underlying point stands: patterns of contact frequently reveal more than the words themselves. Signal deliberately retains almost nothing, when it received a US grand jury subpoena, it could produce only an account creation date and a last connection date, but Signal is the exception, not the rule.

Backups: the hole most people leave open

The third exclusion is the one that catches ordinary users. An end-to-end encrypted chat that is backed up to iCloud or Google Drive leaves the protected channel the moment the backup runs. For years, iCloud backups were encrypted with keys Apple held, meaning Apple could, and did, produce iMessage histories in response to lawful requests even though the messages had been end-to-end encrypted in transit. Apple's Advanced Data Protection, introduced in December 2022, closes that gap, but it is opt-in, and in early 2025 Apple withdrew the feature from the UK entirely rather than comply with a Home Office technical capability notice demanding access. WhatsApp has offered encrypted backups since 2021; the option sits several menus deep and defaults to off. A conversation is only as protected as its least careful participant's backup settings.

Why the political argument misses the target

The recurring Westminster fight, most recently over section 122 of the Online Safety Act 2023, which lets Ofcom require "accredited technology" to scan for child abuse material, is framed as encryption versus child safety. Yet the operational record suggests investigators do not need broken encryption. The EncroChat operation in 2020 worked because French investigators implanted malware on the handsets themselves, harvesting messages before encryption was applied; the National Crime Agency's Operation Venetic turned that feed into more than 3,000 arrests and seizures of over £50 million in cash. ANOM went further: the FBI covertly ran the "secure" phone network, reading every message as it passed. Both were endpoint operations. Neither broke a cipher.

That is the honest shape of the trade-off. Weakening encryption in the pipe would expose everyone's banking, medical records access and private conversations to any attacker who finds the mandated backdoor, while the people with most to hide would move to tools beyond UK jurisdiction. The pipe is the strongest link in the chain. The endpoints, the backups and the metadata are where privacy is genuinely won and lost, for criminals and for everyone else, and any serious conversation about surveillance powers starts there rather than with the arithmetic of the cipher.