Digital Event Horizon
Signal Messenger LLC has released a significant update to its Signal Protocol, a widely used end-to-end encryption engine that powers multiple private chat apps. The update adds protections based on ML-KEM-768, a quantum-resistant key encapsulation mechanism (KEM), and incorporates "ping-pong" behavior to mitigate the risk of quantum computers cracking the protocol. This development marks a significant step towards making Signal fully quantum-resistant.
Signal Messenger LLC has released an update to its end-to-end encryption engine with protections based on ML-KEM-768, a quantum-resistant key encapsulation mechanism (KEM). The upgrade is a major milestone towards making Signal fully quantum-resistant and represents a solid, thoughtful improvement to the existing Signal Protocol. The most significant challenge in developing this upgrade was accounting for larger key sizes required by quantum-resistant algorithms. The new update incorporates "ping-pong" behavior, which limits the number of messages that can be decrypted if an adversary recovers key material. Signal's double ratchet design is a state-of-the-art solution to the challenges posed by quantum computing and offers robust security guarantees.
The world of secure communication is under threat, with the advent of quantum computers poised to render current encryption methods obsolete. However, one organization has taken steps to mitigate this risk and ensure that its messaging platform remains secure in a post-quantum era.
Signal Messenger LLC, the non-profit entity behind the Signal Protocol, has released a significant update to its end-to-end encryption engine. The update, which includes protections based on ML-KEM-768, a quantum-resistant key encapsulation mechanism (KEM), is a major milestone towards making Signal fully quantum-resistant.
The upgrade is the result of extensive research and development by the Signal engineering team, who have been working tirelessly to address the challenges posed by quantum computing. According to Brian LaMacchia, a cryptography engineer who oversaw Microsoft's post-quantum transition from 2015 to 2022, the new update represents "a solid, thoughtful improvement to the existing Signal Protocol."
The most significant challenge in developing this upgrade was accounting for the much larger key sizes that quantum-resistant algorithms require. To address this issue, the Signal team employed a range of optimization techniques, including splitting the KEM computations into smaller steps and using erasure codes to manage asynchrony challenges.
One of the key innovations in the new update is the incorporation of "ping-pong" behavior, which allows parties to take turns replacing ratchet key pairs one at a time. This mechanism is designed to limit the number of messages that can be decrypted if an adversary recovers key material at some point in an ongoing chat.
The ping-pong behavior is made possible by the use of multiple ratchets, with each ratchet working in a single direction and allowing parties to create new keys based on a combination of preceding and newly agreed-upon secrets. This approach ensures that even if an attacker compromises one party's device, they will not be able to learn anything about the keys used earlier.
The Signal Protocol's use of multiple ratchets is a key innovation in secure communication, allowing parties to maintain confidentiality guarantees even in the face of potential compromises. By incorporating this mechanism into the new update, Signal Messenger LLC has taken a significant step towards making its messaging platform fully quantum-resistant.
While the upgrade represents a major achievement, it also highlights the ongoing challenges posed by quantum computing. An adversary capable of monitoring traffic passing from two or more messenger users can capture that data and feed it into a quantum computer—once one of sufficient power is viable—and calculate the ephemeral keys generated in the second ratchet.
In this context, Signal's double ratchet design stands out as state-of-the-art, offering a robust solution to the challenges posed by quantum computing. However, the organization recognizes that even with this upgrade, there will always be risks associated with using any form of encryption.
Ultimately, the release of the updated Signal Protocol represents a triumph for cypherpunks and a significant step towards ensuring secure communication in a post-quantum era. As the world of cryptography continues to evolve, it is clear that organizations like Signal Messenger LLC will play a critical role in shaping the future of secure communication.
Related Information:
https://www.digitaleventhorizon.com/articles/Signal-Protocol-Upgrade-A-Quantum-Leap-Towards-Secure-Messaging-deh.shtml
https://arstechnica.com/security/2025/10/why-signals-post-quantum-makeover-is-an-amazing-engineering-achievement/
Published: Wed Oct 15 03:33:48 2025 by llama3.2 3B Q4_K_M
