Facebook says WhatsApp government snooping “backdoor” is “expected behavior”

Security researchers find backdoor that allows snooping of WhatsApp messages

A University of California security researcher has uncovered a WhatsApp ‘backdoor’ that can be used to intercept and snoop on private encrypted communications sent using the mobile messing service.

A researcher has discovered a security backdoor that can be used to allow Facebook and others to intercept and read encrypted messages of over a billion users that use the WhatsApp mobile messaging service owned by Facebook.

The backdoor was discovered by University of California cryptography and security researcher Tobias Boelter who reported the vulnerability to Facebook in April 2016, according to the Guardian. Instead of fixing the the vulnerability, which the Guardian has confirmed still exists, Facebook responded it was “expected behavior.”

While end users cannot disable the backdoor they can change their security settings to notify them if someone is using the backdoor to spy on their communications by turning on the “Show Security Notifications” setting  which is located under Settings > Account > Security.

WhatsApp has been touted among users by offering end to end encryption which uses unique security keys that users trade and verify to guarantee their communications are secure and cannot be intercepted by a middle man. The backdoor allows administrators to force these keys to be regenerated in a manner unknown to parties involved in a communication which in turn allows for eavesdroppers to intercept and snoop on the communications.

WhatsApp uses the Signal protocol developed by Open Whisper Systems, which is recommended by whistleblower Edward Snowden,  to perform end to end communications of messages. While the Signal protocol is not affected by the vulnerability the WhatsApp implementation automatically resends an undelivered message with a new key without warning the user in advance or giving them the ability to prevent it.

Steffen Tor Jensen, head of information security and digital counter-surveillance at the European-Bahraini Organisation for Human Rights, verified the backdoor still exists, stating “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”.

Open Whisper Systems noted that more advanced users of WhatsApp can configure the applications to inform them if security keys were changed and argued that since some users do monitor key changes the vulnerability shouldn’t really be considered a backdoor.

The Guardian, staking Open Whispers Systems statement into account still insists that governments can use to the vulnerability going as far as suggesting, whether it was originally intended or not, the vulnerability allows WhatsApp to be compliant with a recently passed UK surveillance bill which forces companies to provide the government with backdoors and decryption tools for all products and services.

ss the changes off as a glitch:

From Phys.org

WhatsApp vulnerable to snooping: report

A report says that WhatsApp messages could be read without its billion-plus users knowing due to a security backdoor

The Facebook-owned mobile messaging service WhatsApp is vulnerable to interception, the Guardian newspaper reported on Friday, sparking concern over an app advertised as putting an emphasis on privacy.

The report said that WhatsApp messages could be read without its billion-plus knowing due to a backdoor in the way the company has implemented its end-to-end encryption protocol.

The system relies on unique security keys “that are traded and verified between users to guarantee communications are secure and cannot be intercepted by a middleman,” the report said.

But WhatsApp can force the generation of new encryption keys for offline users “unbeknown to the sender and recipient of the messages,” it said.

Tobias Boelter, a cryptography researcher at the University of California 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.”

Boelter said he had reported the backdoor vulnerability to Facebook in April 2016 and was told that Facebook was already aware of the issue but that it was not actively being worked on.

The company said in a statement that it provided a “simple, fast, reliable and secure” service.

It said there was a way of notifying users when a contact’s security code had changed.

“We know the most common reasons this happens are because someone has switched phones or reinstalled WhatsApp…. In these situations, we want to make sure people’s messages are delivered, not lost in transit,” it said in a statement.

But the Guardian said it had verified that the security backdoor still exists.

The paper quoted Steffen Tor Jensen, head of information security and digital counter-surveillance at the European-Bahraini Organisation for Human Rights, saying: “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”.

Facebook bought WhatsApp in 2014 but it continues to operate as a separate app.

Read more at: https://phys.org/news/2017-01-whatsapp-vulnerable-snooping.html#jCp

Guardian:

WhatsApp vulnerability allows snooping on encrypted messages

Exclusive: Privacy campaigners criticise WhatsApp vulnerability as a ‘huge threat to freedom of speech’ and warn it could be exploited by government agencies

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, 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 WhatsApp has implemented its end-to-end encryption protocol.

Privacy campaigners said the vulnerability is a “huge threat to freedom of speech” and warned it could be used by government agencies as a backdoor to snoop on users who believe their messages to be secure.

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 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, 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 behavior” 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.”

Boelter said: “[Some] might say that this vulnerability could only be abused to snoop on ‘single’ targeted messages, not entire conversations. This is not true if you consider that the WhatsApp server can just forward messages without sending the ‘message was received by recipient’ notification (or the double tick), which users might not notice. Using the retransmission vulnerability, the WhatsApp server can then later get a transcript of the whole conversation, not just a single message.”

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.”

A WhatsApp spokesperson told the Guardian: “Over 1 billion people use WhatsApp today because it is simple, fast, reliable and secure. At WhatsApp, we’ve always believed that people’s conversations should be secure and private. Last year, we gave all our users a better level of security by making every message, photo, video, file and call end-to-end encrypted by default. As we introduce features like end-to-end encryption, we focus on keeping the product simple and take into consideration how it’s used every day around the world.

“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.”

Concerns over the privacy of WhatsApp users has been repeatedly highlighted since Facebook acquired the company for $22bn in 2014. In August 2015, Facebook announced a change to the privacy policy governing WhatsApp that allowed the social network to merge data from WhatsApp users and Facebook, including phone numbers and app usage, for advertising and development purposes.

Facebook halted the use of the shared user data for advertising purposes in November after pressure from the pan-European data protection agency group Article 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.

From Open Whispers System:

There is no WhatsApp ‘backdoor’

Today, the Guardian published a story falsely claiming that WhatsApp’s end to end encryption contains a “backdoor.”

Background

WhatsApp’s encryption uses Signal Protocol, as detailed in their technical whitepaper. In systems that deploy Signal Protocol, each client is cryptographically identified by a key pair composed of a public key and a private key. The public key is advertised publicly, through the server, while the private key remains private on the user’s device.

This identity key pair is bound into the encrypted channel that’s established between two parties when they exchange messages, and is exposed through the “safety number” (aka “security code” in WhatsApp) that participants can check to verify the privacy of their communication.

Most end-to-end encrypted communication systems have something that resembles this type of verification, because otherwise an attacker who compromised the server could lie about a user’s public key, and instead advertise a key which the attacker knows the corresponding private key for. This is called a “man in the middle” attack, or MITM, and is endemic to public key cryptography, not just WhatsApp.

The issue

One fact of life in real world cryptography is that these keys will change under normal circumstances. Every time someone gets a new device, or even just reinstalls the app, their identity key pair will change. This is something any public key cryptography system has to deal with. WhatsApp gives users the option to be notified when those changes occur.

While it is likely that not every WhatsApp user verifies safety numbers or safety number changes, the WhatsApp clients have been carefully designed so that the WhatsApp server has no knowledge of whether users have enabled the change notifications, or whether users have verified safety numbers. WhatsApp could try to “man in the middle” a conversation, just like with any encrypted communication system, but they would risk getting caught by users who verify keys.

Under normal circumstances, when communicating with a contact who has recently changed devices or reinstalled WhatsApp, it might be possible to send a message before the sending client discovers that the receiving client has new keys. The recipient’s device immediately responds, and asks the sender to reencrypt the message with the recipient’s new identity key pair. The sender displays the “safety number has changed” notification, reencrypts the message, and delivers it.

The WhatsApp clients have been carefully designed so that they will not re-encrypt messages that have already been delivered. Once the sending client displays a “double check mark,” it can no longer be asked to re-send that message. This prevents anyone who compromises the server from being able to selectively target previously delivered messages for re-encryption.

The fact that WhatsApp handles key changes is not a “backdoor,” it is how cryptography works. Any attempt to intercept messages in transmit by the server is detectable by the sender, just like with Signal, PGP, or any other end-to-end encrypted communication system.

The only question it might be reasonable to ask is whether these safety number change notifications should be “blocking” or “non-blocking.” In other words, when a contact’s key changes, should WhatsApp require the user to manually verify the new key before continuing, or should WhatsApp display an advisory notification and continue without blocking the user.

Given the size and scope of WhatsApp’s user base, we feel that their choice to display a non-blocking notification is appropriate. It provides transparent and cryptographically guaranteed confidence in the privacy of a user’s communication, along with a simple user experience. The choice to make these notifications “blocking” would in some ways make things worse. That would leak information to the server about who has enabled safety number change notifications and who hasn’t, effectively telling the server who it could MITM transparently and who it couldn’t; something that WhatsApp considered very carefully.

Even if others disagree about the details of the UX, under no circumstances is it reasonable to call this a “backdoor,” as key changes are immediately detected by the sender and can be verified.

The reporting

The way this story has been reported has been disappointing. There are many quotes in the article, but it seems that the Guardian put very little effort into verifying the original technical claims they’ve made. Even though we are the creators of the encryption protocol supposedly “backdoored” by WhatsApp, we were not asked for comment.

Instead, most of the quotes in the story are from policy and advocacy organizations who seem to have been asked “WhatsApp put a backdoor in their encryption, do you think that’s bad?”

We believe that it is important to honestly and accurately evaluate the choices that organizations like WhatsApp or Facebook make. There are many things to criticize Facebook for; running a product that deployed end-to-end encryption by default for over a billion people is not one of them.

It is great that the Guardian thinks privacy is something their readers should be concerned about. However, running a story like this without taking the time to carefully evaluate claims of a “backdoor” will ultimately only hurt their readers. It has the potential to drive them away from a well engineered and carefully considered system to much more dangerous products that make truly false claims. Since the story has been published, we have repeatedly reached out to the author and the editors at the Guardian, but have received no response.

We believe that WhatsApp remains a great choice for users concerned with the privacy of their message content.

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