WhatsApp, Signal, and dangerously ignorant journalism


Image Credits:

Jon Evans


Jon Evans is the CTO of the engineering consultancy HappyFunCorp; the award-winning author of six novels, one graphic novel, and a book of travel writing; and TechCrunch’s weekend columnist since 2010.

More posts from Jon Evans

There is something about encryption that brings out the worst in journalists. Because to most of them it is magic, they are always searching desperately for the proverbial man behind the curtain, without knowing what to look for. Which may explain The Guardian’s recent bizarre attack on WhatsApp, which they accused, wrongly, of having a “backdoor.” And the security community erupted in rage.

To understand this story, why the Guardian was and is wrong, why they were forced to walk back their original “backdoor” headline, and why the security community is furious, you’ll need a little context. Sit down, my pretties, and let me tell you a little infosec fable:

Once upon a time there was PGP, which stands for Pretty Good Privacy, and it was good and strong. So good and strong that after its creator, Phil Zimmerman, released its source code 25 years ago, the US government opened a criminal investigation against him for arms trafficking. (The case was later dropped without indictment.)

For twenty years PGP was the gold standard of secure messaging. The NSA could not break it. Edward Snowden used it. But it had serious flaws. For one, it lacked forward secrecy; if your key was compromised, so was every message it had ever encrypted. For another, key exchange was/is at best challenging.

But the worst thing about PGP, by far, is that it is fiendishly user-hostile, so only hardcore hackers ever really used it. (The Snowden revelations were delayed by a month because he couldn’t find a way to contact Glenn Greenwald securely.)

Just as the best workout routine is not the Rock’s but, rather, one that you will actually stick to, the most secure messaging system is one that you will actually use. Whether we like it or not, usability is an essential aspect of security. Any “secure” systems which pretend this is not true will fail from disuse.

Enter Signal, a mobile (and Chrome plug-in) secure messaging system. It is fast, slick, sexy, cross-platform, and battle-tested. It implements highly secure end-to-end messaging with a “ratchet” protocol which provides perfect forward secrecy. It is the choice of technically sophisticated, security-conscious people around the world. It is not perfect. No system is perfect. Every system requires compromises. But Signal is the best available alternative.

However, most of the world does not use Signal. Most of the world uses SMS, Facebook Messenger, and, especially, WhatsApp — which, until recently, was much less secure. So the roll-out of the Signal protocol to WhatsApp, which commenced two years ago, was met with rejoicing. However, even though it used the same protocol as Signal, the implementation was different. It’s that difference which the Guardian, strangely and wrongly, called a “back door.”

For the grotty details see “A Trade-Off In Whatsapp Is Called A Backdoor” by the EFF, “There Is No Whatsapp Backdoor” by Signal head honcho Moxie Marlinspike, “WhatsApp Security Vulnerability” by Bruce Schneier, and “On the ‘WhatsApp backdoor’, Trade-Offs and Opportunistic Authentication,” by Frederic Jacobs. (edit: a previous link here was replaced because of a consensus that it its characterization of Wire, a completely different private-messaging app, was unfair/inaccurate.)

The essential problem is that when the person you’re talking to gets a new phone, or re-installs the app, there’s no way to be immediately sure that the new installation is them. In theory, you should communicate with them over a different medium to verify they aren’t someone else pretending to be them; in a perfect world, you would use the tools Signal and WhatsApp provide to be mathematically certain of this. In practice, though, essentially nobody does this.

Signal, which was built for technically sophisticated users, refuses to send any new messages to a person whose identity seems to have changed, until and unless you explicitly tell it to do so. WhatsApp, which had an install base of roughly a billion users, the vast majority of them anything but technically sophisticated, when it rolled out the Signal protocol — decided that doing so would confuse their users and cause conversations to be lost, and that continuing to deliver messages was more important than making users explicitly ensure their security.

Whether they were right to do so is a thing about which reasonable people can disagree. Again, all messaging systems involve security compromises; and all messaging systems require that you trust somebody, sometimes. The Guardian was my newspaper of choice when I lived in the UK, and I’ve written for them myself, but it is deeply irresponsible journalism to suggest that a complex compromise with which some people disagree is a “back door” or a profound concealed vulnerability.

On one hand, WhatsApp’s implementation of the Signal protocol is less secure than Signal’s implementation. On the other, it is far more secure than their previous system — and the only entity able to use this vulnerability to hack WhatsApp messages is WhatsApp itself, or an intruder who compromises WhatsApp’s systems. Furthermore, as Schneier points out, “it’s an attack against current and future messages, and not something that would allow the government to reach into the past. In that way, it is no more troubling than the government hacking your mobile phone and reading your WhatsApp conversations that way.”

More to the point, though, WhatsApp’s users already have to trust WhatsApp. For all they actually, verifiably know, the app isn’t implementing the Signal Protocol at all. They also have to trust Apple, Google, or whoever they downloaded the app from. They have to trust that no malware on their phone is registering their keytaps and taking surreptitious screenshots. They have to trust that the operating system provides the entropy the encryption algorithms need. You always have to trust somebody. It’s inevitable. Even if you compile PGP from scratch, you can’t go over its code line-by-line to be certain it’s secure — and even if you did, what about the kernel? What about the compiler?

Real security design is about navigating the compromises between usability and security, determining the sophistication and threat model of your users, deciding who you have to trust and who you can’t afford to. Signal makes compromises too — in particular, its use of your phone number. Security design is a complex and ambiguous task not made any easier by ignorant gotcha journalism that can’t distinguish between an disputable compromise and a “backdoor.”

This is not an abstruse, theoretical issue: this hurts and endangers real people, en masse. Saying “Switch to Signal” ignores the fact that most people’s contacts won’t do so, so their de facto choice, if they need to communicate, is between WhatsApp and SMS — and if you frighten them off the former, you scare them into the incredibly vulnerable arms of the latter. Those at the Guardian responsible for this ugly mess have much to answer for. You don’t need to take my word for it — but you should take the word of this who’s who of the security world.

More TechCrunch

Welcome back to TechCrunch’s Week in Review. This week had two major events from OpenAI and Google. OpenAI’s spring update event saw the reveal of its new model, GPT-4o, which…

OpenAI and Google lay out their competing AI visions

Expedia says Rathi Murthy and Sreenivas Rachamadugu, respectively its CTO and senior vice president of core services product & engineering, are no longer employed at the travel booking company. In…

Expedia says two execs dismissed after ‘violation of company policy’

When Jeffrey Wang posted to X asking if anyone wanted to go in on an order of fancy-but-affordable office nap pods, he didn’t expect the post to go viral.

With AI startups booming, nap pods and Silicon Valley hustle culture are back

OpenAI’s Superalignment team, responsible for developing ways to govern and steer “superintelligent” AI systems, was promised 20% of the company’s compute resources, according to a person from that team. But…

OpenAI created a team to control ‘superintelligent’ AI — then let it wither, source says

A new crop of early-stage startups — along with some recent VC investments — illustrates a niche emerging in the autonomous vehicle technology sector. Unlike the companies bringing robotaxis to…

VCs and the military are fueling self-driving startups that don’t need roads

When the founders of Sagetap, Sahil Khanna and Kevin Hughes, started working at early-stage enterprise software startups, they were surprised to find that the companies they worked at were trying…

Deal Dive: Sagetap looks to bring enterprise software sales into the 21st century

Keeping up with an industry as fast-moving as AI is a tall order. So until an AI can do it for you, here’s a handy roundup of recent stories in the world…

This Week in AI: OpenAI moves away from safety

After Apple loosened its App Store guidelines to permit game emulators, the retro game emulator Delta — an app 10 years in the making — hit the top of the…

Adobe comes after indie game emulator Delta for copying its logo

Meta is once again taking on its competitors by developing a feature that borrows concepts from others — in this case, BeReal and Snapchat. The company is developing a feature…

Meta’s latest experiment borrows from BeReal’s and Snapchat’s core ideas

Welcome to Startups Weekly! We’ve been drowning in AI news this week, with Google’s I/O setting the pace. And Elon Musk rages against the machine.

Startups Weekly: It’s the dawning of the age of AI — plus,  Musk is raging against the machine

IndieBio’s Bay Area incubator is about to debut its 15th cohort of biotech startups. We took special note of a few, which were making some major, bordering on ludicrous, claims…

IndieBio’s SF incubator lineup is making some wild biotech promises

YouTube TV has announced that its multiview feature for watching four streams at once is now available on Android phones and tablets. The Android launch comes two months after YouTube…

YouTube TV’s ‘multiview’ feature is now available on Android phones and tablets

Featured Article

Two Santa Cruz students uncover security bug that could let millions do their laundry for free

CSC ServiceWorks provides laundry machines to thousands of residential homes and universities, but the company ignored requests to fix a security bug.

1 day ago
Two Santa Cruz students uncover security bug that could let millions do their laundry for free

TechCrunch Disrupt 2024 is just around the corner, and the buzz is palpable. But what if we told you there’s a chance for you to not just attend, but also…

Harness the TechCrunch Effect: Host a Side Event at Disrupt 2024

Decks are all about telling a compelling story and Goodcarbon does a good job on that front. But there’s important information missing too.

Pitch Deck Teardown: Goodcarbon’s $5.5M seed deck

Slack is making it difficult for its customers if they want the company to stop using its data for model training.

Slack under attack over sneaky AI training policy

A Texas-based company that provides health insurance and benefit plans disclosed a data breach affecting almost 2.5 million people, some of whom had their Social Security number stolen. WebTPA said…

Healthcare company WebTPA discloses breach affecting 2.5 million people

Featured Article

Microsoft dodges UK antitrust scrutiny over its Mistral AI stake

Microsoft won’t be facing antitrust scrutiny in the U.K. over its recent investment into French AI startup Mistral AI.

1 day ago
Microsoft dodges UK antitrust scrutiny over its Mistral AI stake

Ember has partnered with HSBC in the U.K. so that the bank’s business customers can access Ember’s services from their online accounts.

Embedded finance is still trendy as accounting automation startup Ember partners with HSBC UK

Kudos uses AI to figure out consumer spending habits so it can then provide more personalized financial advice, like maximizing rewards and utilizing credit effectively.

Kudos lands $10M for an AI smart wallet that picks the best credit card for purchases

The EU’s warning comes after Microsoft failed to respond to a legally binding request for information that focused on its generative AI tools.

EU warns Microsoft it could be fined billions over missing GenAI risk info

The prospects for troubled banking-as-a-service startup Synapse have gone from bad to worse this week after a United States Trustee filed an emergency motion on Wednesday.  The trustee is asking…

A US Trustee wants troubled fintech Synapse to be liquidated via Chapter 7 bankruptcy, cites ‘gross mismanagement’

U.K.-based Seraphim Space is spinning up its 13th accelerator program, with nine participating companies working on a range of tech from propulsion to in-space manufacturing and space situational awareness. The…

Seraphim’s latest space accelerator welcomes nine companies

OpenAI has reached a deal with Reddit to use the social news site’s data for training AI models. In a blog post on OpenAI’s press relations site, the company said…

OpenAI inks deal to train AI on Reddit data

X users will now be able to discover posts from new Communities that are trending directly from an Explore tab within the section.

X pushes more users to Communities

For Mark Zuckerberg’s 40th birthday, his wife got him a photoshoot. Zuckerberg gives the camera a sly smile as he sits amid a carefully crafted re-creation of his childhood bedroom.…

Mark Zuckerberg’s makeover: Midlife crisis or carefully crafted rebrand?

Strava announced a slew of features, including AI to weed out leaderboard cheats, a new ‘family’ subscription plan, dark mode and more.

Strava taps AI to weed out leaderboard cheats, unveils ‘family’ plan, dark mode and more

We all fall down sometimes. Astronauts are no exception. You need to be in peak physical condition for space travel, but bulky space suits and lower gravity levels can be…

Astronauts fall over. Robotic limbs can help them back up.

Microsoft will launch its custom Cobalt 100 chips to customers as a public preview at its Build conference next week, TechCrunch has learned. In an analyst briefing ahead of Build,…

Microsoft’s custom Cobalt chips will come to Azure next week

What a wild week for transportation news! It was a smorgasbord of news that seemed to touch every sector and theme in transportation.

Tesla keeps cutting jobs and the feds probe Waymo