A vulnerability in WhatsApp’s end-to-end encryption creates a potential mechanism for Facebook and others to intercept and read encrypted messages, reports claimed today.
In a statement (below), WhatsApp said that the feature is necessary to allow messages to be delivered in parts of the world where people frequently swap devices and SIM cards, an explanation that has failed to mollify critics.
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.
The flaw in WhatsApp’s encryption was discovered by Tobias Beolter, a cryptography and security researcher at the University of California. The security shortcoming meant that Facebook (which owns WhatApp) could access to user’s messages, contradicting claims that no one could intercept them. Hackers and governments might also be able to abuse the backdoor.
End-to-end encryption means only the recipient and sender have the keys to unlock their messages. The approach is secure, but only if the protocol is implemented correctly.
Third party security firms are critical of Facebook’s design decisions in rolling out end-to-end encryption.
Neil Cook, Chief Security Architect at Open-Xchange, commented: “WhatsApp has already broken their promise not to share user data with Facebook, and now it seems that their promise of end-to-encrypted messaging isn’t quite as secure as everyone had hoped, particularly given the involvement of Open Whisper Systems. It’s worth noting that this error in the encryption protocol is not present in Signal, so the team at WhatsApp have made the change intentionally.”
Matthew Aldridge, solutions architect at Webroot, said: “This flaw allows Facebook/WhatsApp to intercept messages if they choose to, by having the sender’s software automatically flip across to a second encryption key. The functionality is designed to create a seamless user experience for users who have connectivity issues or drop offline for a time during a conversation, but it has resulted in a situation where it could be used to intercept messages by WhatsApp. For those sending highly sensitive messages, or simply looking to avoid this, you should switch on the key change warnings in settings, and always check that the two ticks appear after sending messages in an active conversation.”
Others fault Facebook for failing to respond quickly enough.
Jacob Ginsberg, senior director at Echoworx, an expert in end-to-end messaging encryption, said: “The fact that Facebook has known about this vulnerability since April is doubly damming. Not only could this be seen by many as supporting on-going government data collection interventions, it means their talk of encryption and privacy has been nothing more than lip service. The company needs to actively address its security measures.”
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