A security vulnerability that can be used to allow Facebook and others to intercept and read encrypted messages has been found within its WhatsApp messaging service.
FACEBOOK CLAIMS THAT NO ONE CAN INTERCEPT WHATSAPP MESSAGES
Facebook claims that no one can intercept WhatsApp messages, not even the company and its staff, ensuring privacy for its billion-plus users. But new research shows that the company could in fact read messages due to the way WhatsApphas implemented its end-to-end encryption protocol.
WhatsApp has made privacy and security a primary selling point, and has become a go to communications tool of activists, dissidents and diplomats.
WHATSAPP’s END TO END ENCRYPTION RELIES ON THE GENERATION OF UNIQUE
WhatsApp’s end-to-end encryption relies on the generation of unique security keys, using the acclaimed Signal protocol, developed by Open Whisper Systems, that are traded and verified between users to guarantee communications are secure and cannot be intercepted by a middleman.
However, WhatsApp has the ability to force the generation of new encryption keys for offline users, unbeknown to the sender and recipient of the messages, and to make the sender re-encrypt messages with new keys and send them again for any messages that have not been marked as delivered.
The recipient is not made aware of this change in encryption, while the sender is only notified if they have opted-in to encryption warnings in settings, and only after the messages have been re-sent. This re-encryption and rebroadcasting effectively allows WhatsApp to intercept and read users’ messages.
THE SECURITY LOOPHOLE WAS DISCOVERED BY TOBIAS BOELTER
The security loophole was discovered by Tobias Boelter, a cryptography and security researcher at the University of California, Berkeley. He told the Guardian: “If WhatsApp is asked by a government agency to disclose its messaging records, it can effectively grant access due to the change in keys.”
The vulnerability is not inherent to the Signal protocol. Open Whisper Systems’ messaging app, Signal, the app used and recommended by whistleblower Edward Snowden, does not suffer from the same vulnerability. If a recipient changes the security key while offline, for instance, a sent message will fail to be delivered and the sender will be notified of the change in security keys without automatically resending the message.
WhatsApp’s implementation automatically resends an undelivered message with a new key without warning the user in advance or giving them the ability to prevent it.
Boelter reported the vulnerability to Facebook in April 2016, but was told that Facebook was aware of the issue, that it was “expected behaviour” and wasn’t being actively worked on. The Guardian has verified the loophole still exists.
Steffen Tor Jensen, head of information security and digital counter-surveillance at the European-Bahraini Organisation for Human Rights, verified Boelter’s findings. He said: “WhatsApp can effectively continue flipping the security keys when devices are offline and re-sending the message, without letting users know of the change till after it has been made, providing an extremely insecure platform.”
The vulnerability calls into question the privacy of messages sent across the service, which is used around the world, including by people living in oppressive regimes.
Professor Kirstie Ball, co-director and founder of the Centre for Research into Information, Surveillance and Privacy, called the existence of a vulnerability within WhatsApp’s encryption “a gold mine for security agencies” and “a huge betrayal of user trust”. She added: “It is a huge threat to freedom of speech, for it to be able to look at what you’re saying if it wants to. Consumers will say, I’ve got nothing to hide, but you don’t know what information is looked for and what connections are being made.”
In the UK, the recently passed Investigatory Powers Act allows the government to intercept bulk data of users held by private companies, without suspicion of criminal activity, similar to the activity of the US National Security Agency uncovered by the Snowden revelations. The government also has the power to force companies to “maintain technical capabilities” that allow data collection through hacking and interception, and requires companies to remove “electronic protection” from data. Intentional or not, WhatsApp’s vulnerability to the end-to-end encryption could be used in such a way to facilitate government interception.
Jim Killock, executive director of Open Rights Group, said: “If companies claim to offer end-to-end encryption, they should come clean if it is found to be compromised….In the UK, the Investigatory Powers Act means that technical capability notices could be used to compel companies to introduce flaws – which could leave people’s data vulnerable.”
“In WhatsApp’s implementation of the Signal protocol, we have a “Show Security Notifications” setting (option under Settings > Account > Security) that notifies you when a contact’s security code has changed. We know the most common reasons this happens are because someone has switched phones or reinstalled WhatsApp. This is because in many parts of the world, people frequently change devices and Sim cards. In these situations, we want to make sure people’s messages are delivered, not lost in transit.”
Asked to comment specifically on whether Facebook/WhatApps had accessed users’ messages and whether it had done so at the request of government agencies or other third parties, it directed the Guardian to its site that details aggregate data on government requests by country.
WhatsApp later issued another statement saying: “WhatsApp does not give governments a ‘backdoor’ into its systems and would fight any government request to create a backdoor.”
Facebook halted the use of the shared user data for advertising purposes in November after pressure from the pan-European data protection agency groupArticle 29 Working Party in October. The European commission then filed charges against Facebook for providing “misleading” information in the run-up to the social network’s acquisition of messaging service WhatsApp, following its data-sharing change.