Google Chrome Post-Quantum Cryptography issue: Here is what we know about it. Quick Look

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Google Chrome Post-Quantum Cryptography issue: Here is what we know about it. Quick Look

Google Chrome, a popular web browser, has recently introduced a new feature that is making waves in the digital world. This feature, known as post-quantum cryptography, is designed to protect users’ data from future threats posed by quantum computers. However, it seems to be a double-edged sword, as it may cause issues with Transport Layer Security (TLS) connections.

The Quantum Leap by Google Chrome

Post-quantum cryptography is a type of encryption that is resistant to attacks from both classical and quantum computers. Google started testing this secure TLS key encapsulation mechanism in August and has now enabled it in the latest Chrome version for all users. The new version utilizes the Kyber768 quantum-resistant key agreement algorithm for TLS 1.3 and QUIC connections to protect Chrome TLS traffic against quantum cryptanalysis.

The Issue at Hand for Google Chrome

Despite its promising features, some Google Chrome users have reported having issues connecting to websites, servers, and firewalls after the release of Chrome 124, which has the new quantum resistant X25519Kyber768 encapsulation mechanism enabled by default. The problem also affects various network devices from multiple vendors.

The Root Cause

These connection issues are not caused by a bug in Google Chrome. Instead, they are caused by web servers failing to properly implement Transport Layer Security (TLS) and not being able to handle larger ClientHello messages for post-quantum cryptography. This causes them to reject connections that use the Kyber768 quantum-resistant key agreement algorithm rather than switching to classic cryptography if they don’t support X25519Kyber768.

The Solution

Affected Google Chrome users can mitigate the issue by going to chrome://flags/#enable-tls13-kyber and disabling the TLS 1.3 hybridized Kyber support in Chrome. Additionally, developers can fix the bug by properly implementing TLS and handling larger ClientHello messages.


While post-quantum cryptography is a significant step forward in securing our digital world against future threats, it’s clear that there are still some kinks to be worked out. As we continue to innovate and improve our technology, it’s crucial to keep in mind the potential impacts and be prepared to address any issues that may arise.

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