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The Zoom Settlement and When “End-to-End Encryption” Isn’t End-to-End

Ciphr Team
February 15, 2021 - 9 min read

What is End-to-End Encryption?

End-to-end encryption refers to the practice of encrypting a message from its sender to its recipient. This means that the data cannot be read by anyone else as it is travelling from the sender to the recipient, not even the provider of the communications platform.

When discussing end-to-end encryption, it is important to understand its limitations. End-to-end encryption protects data in transit. If an attacker has access to the message before it is encrypted or after it is decrypted, then they can read it.

Inside the Zoom End-to-End Encryption Settlement

During the surge in telework driven by COVID-19, Zoom (and other collaboration platforms) got a lot of attention. Suddenly they were the primary means by which people stayed in contact and did business. As a part of this, Zoom underwent a great deal of security scrutiny and came up lacking.

Zoom claimed that it offered end-to-end encryption of its video meetings, but it didn’t. Video data was decrypted on the organization’s servers, potentially allowing the organization or any attackers with access to its network unauthorized access to meetings. When pressed, the company claimed that it was using a different definition of end-to-end encryption than the rest of the industry.

Based on Zoom’s claims about end-to-end encryption, the US Federal Trade Commission (FTC) launched an investigation into the company. The charges against Zoom included deceptive advertising (over the fake end-to-end encryption), storing unencrypted videos on its servers for up to two months, and endangering user security by installing an unauthorized web server on users’ machines so that they could join meetings more quickly. In November 2020, Zoom and the FTC settled, with Zoom required to improve its security and refrain from deceptive advertising in the future.

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Where End-to-End Encryption Can Go Wrong

As Zoom demonstrated, definitions of “end-to-end encryption” can vary dramatically. A real end-to-end encryption solution will not allow anyone but the participants in a conversation to access it. However, the security provided by end-to-end encryption can be broken or undermined in a variety of different ways.

Mistaking Transport-Level Encryption for E2EE

The use of transport-level encryption, such as SSL and TLS, as a substitute for end-to-end encryption is the mistake that Zoom made. The mistaken claim that these two are equivalent is the basis for the FTC suit against them.

The majority of Internet traffic uses transport-level encryption like SSL and TLS. These protocols are designed to encrypt traffic between a client and a server, making it impossible for an eavesdropper to read the data in transit.

This differs from end-to-end encryption because, in the case of Zoom and similar platforms, the Zoom server is acting as an intermediary between two or more clients and forwarding traffic between them. It does this by maintaining a different encrypted link with each client. However, data is decrypted at the server, breaking the end-to-end encryption and placing it at risk of exposure or unauthorized use.

Provider-Owned Keys

Even if end-to-end encryption is actually end-to-end, it doesn’t mean that it is implemented properly. If a platform provider has access to or control over the encryption keys, then the benefits of end-to-end encryption are essentially negated.

Some collaboration platforms, like GoToMeeting, offer end-to-end encryption where the platform generates and provides the encryption keys. In the case of GoToMeeting, the platform creates a seed from which the key is derived, provides that seed to all participants, and deletes its copy of the seed once the meeting is over.

The problem with this approach to end-to-end encryption is that, while the traffic is encrypted end-to-end, it doesn’t need to stay that way. A platform provider with access to the decryption key could choose to decrypt the traffic as it flows through their servers. This places the confidentiality of the data at risk of exposure to the platform provider and any cybercriminal that gains access to their key derivation or storage servers.

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Weak/Broken Encryption

End-to-end encryption is only useful if it is based off of a strong encryption algorithm. If the algorithm itself is weak or implemented in an insecure way, then an attacker could take advantage of its weaknesses to read the encrypted data.

The use of custom encryption algorithms or protocols can easily break encryption, as demonstrated by the recent Zerologon vulnerability. If end-to-end encryption uses a custom algorithm or implementation, it may be breakable.

Backdoored Encryption

Representatives of seven countries (U.S., U.K., Australia, New Zealand, Canada, India, and Japan) have pushed to force software companies to build backdoors into their end-to-end encryption algorithms.

The basis for this argument is that law enforcement is incapable of accessing communications protected by strong encryption. US. Attorney General William Barr has suggested three methods (none of which are new) for accomplishing this:

● Backdoored Software: One suggestion is to make messaging application creators add a backdoor that allows access to messages before or after they are encrypted. The NSA tried this before with Juniper firewalls, enabling anyone to gain access to the networks they protected once the backdoor credentials were leaked.

● Key Escrow: A key escrow system would hold master decryption keys, ideally in a way that only law enforcement could access and only when authorized to do so. The problem with this is that no-one knows how to implement it in a way that is both usable and secure.

● Layered Encryption: A paper by Matt Tait (formerly of GCHQ) describes the concept of layered cryptographic envelopes, which could be used to provide law enforcement access to data when needed. Again, while this may work in theory, no-one knows how to implement it effectively in practice.

Although there is increasing rhetoric about requiring backdoors, it is unlikely to happen. Once you open the backdoor, it’s not just law enforcement who has potential access to data – cybercriminals could also make use of it. Protecting secure communications is incredibly important.

Selecting a Secure Messaging Solution

End-to-end encryption is a valuable tool and essential for personal security and privacy. However, it is important to choose a messaging platform that actually offers strong end-to-end encryption.

When evaluating messaging applications, take a look at how their encryption is described. An important thing to look for is user-controlled keys. A platform that has these can’t be making the same mistakes as Zoom and GoToMeeting.

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