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New Quantum Protocol Enables Secure Communication Among Multiple Users
Confirmed
In Short: The Signal Protocol, first published in 2013, has been adopted by major messaging products and is used by billions of people worldwide for end-to-end encrypted communications.
Signal Messenger has announced the introduction of the Sparse Post Quantum Ratchet (SPQR), a new advancement in the Signal Protocol designed to bolster security against potential quantum computing threats.
SPQR is the next step in Signal's quantum resistance strategy, following the earlier PQXDH upgrade which incorporated quantum-resistant cryptographic secrets.
The new ratchet, when combined with Signal’s existing Double Ratchet, forms a Triple Ratchet system that maintains the protocol’s existing security guarantees of forward secrecy and post-compromise security.
Graeme Connell and Rolfe Schmidt, developers at Signal, highlighted the importance of SPQR in a blog post, emphasizing its role in enhancing the resilience of the Signal Protocol against future quantum computing threats.
Meanwhile, an armed incident occurred at a campaign event for Ohio Democratic gubernatorial nominee Dr. Amy Acton at the Canfield Fair, where an assailant lunged at her, injuring multiple people.
Chris Anderson, Mahoning County Democratic Party chairman, stated that the suspect was armed with multiple weapons and knocked volunteers to the ground.
Connie Luck, communications director for Republican gubernatorial nominee Vivek Ramaswamy, condemned the incident, stating that candidates should be able to meet voters without threats or violence.
In parallel, researchers at Nanjing University have demonstrated a measurement-device-independent quantum cryptographic conferencing (MDI-QCC) network, an important step toward building practical multi-user quantum communication systems.
This advancement, which allows multiple users to share a single secure key, offers immunity to attacks targeting detection systems and represents a move beyond two-user quantum key distribution towards a more scalable quantum internet.
What this adds
The incident at the Canfield Fair highlights the ongoing security concerns for political figures, separate from the technological advancements in quantum communication.
The MDI-QCC network demonstrated by Nanjing University researchers represents a significant step in the development of practical multi-user quantum communication systems, enhancing security and scalability.
What's confirmed
- Technical information on the Signal Protocol can be found in the specifications section of our docs site.
- In a previous blog post, we announced the first step towards advancing quantum resistance for the Signal Protocol: an upgrade called PQXDH that incorporates quantum-resistent cryptographic secrets when chat sessions are established in order to protect against harvest-now-decrypt-later attacks that could allow current chat sessions to become compromised if a sufficiently powerful quantum computer is developed in the future.
- Today, we are happy to announce the next step in advancing quantum resistance for the Signal Protocol: an additional regularly advancing post-quantum ratchet called the Sparse Post Quantum Ratchet, or SPQR.
- Mean ol’ Mallory records the entire (encrypted) communication, and really wants to know what Alice and Bob are talking about.
- Signal >> Blog >> Signal Protocol and Post-Quantum Ratchets Get Signal Help Blog Developers Careers Donate Signal Protocol and Post-Quantum Ratchets Graeme Connell and Rolfe Schmidt on 02 Oct 2025 We are excited to announce a significant advancement in the security of the Signal Protocol: the introduction of the Sparse Post Quantum Ratchet (SPQR).
- This new ratchet enhances the Signal Protocol’s resilience against future quantum computing threats while maintaining our existing security guarantees of forward secrecy and post-compromise security.
- The Signal Protocol is a set of cryptographic specifications that provides end-to-end encryption for private communications exchanged daily by billions of people around the world.
- After its publication in 2013, the open source Signal Protocol was adopted not only by the Signal application but also by other major messaging products.
- However, the Signal Protocol isn’t just about protecting cryptographic material and keys at the beginning of a new chat or phone call; it’s also designed to minimize damage and heal from compromise as that conversation continues.
- On its own, SPQR provides secure messaging that provably achieves these FS and PCS guarantees in a quantum safe manner.
- We mix the output of this new ratcheting protocol with Signal’s existing Double Ratchet, in a combination we refer to as the Triple Ratchet.
- Acton at the Canfield Fair: Addie Bullock, Communications Director for the Acton campaign.
What's still developing
- Havas, 38, busted into the Mahoning County Democratic Party tent and pushed his way to the front, knocking multiple volunteers to the ground in the process, Mahoning County Democratic Party Chair Chris Anderson wrote in a statement on social media.
- FP Markets analyst Aaron Hill said the shift represents a return from the Bernanke era transparency framework to the more opaque Greenspan-style of communication.
- The shift, confirmed across multiple public statements, marks one of the most significant changes in monetary policy communication since the post 2008 period.
- Brianna Nargiso is a graduate of the Howard University Cathy Hughes School of Communications with a major in media, journalism, and film, and a minor in political science.
- With a passion for social justice, education, and public health, Brianna has contributed to multiple publications, including Flintside, The Root, 101 Magazine, Howard University News Service, and many others.
- By the time the game kicked off, power was only back in a limited capacity, forcing the teams to be without coach-to-player communication technology, no iPad’s on the sidelines, no public address announcer, no stadium clock, and no working scoreboard.
- See also: West Palm Beach launches West Palm Move, replacing RideWPB service Multiple reports say that the reason for the major power outage was caused by a transformer going out on the west side of the stadium.
- Local reports also said the suspect was allegedly armed with multiple weapons and that several campaign volunteers were knocked to the ground during the confrontation, although authorities had not publicly confirmed those details as of Sunday evening.
- According to the researchers, this work confirms the protocol’s feasibility and establishes a benchmark for future MDI-QCC networks aiming for higher key rates and extended communication distances.
- This advancement coincides with complementary work from the Southern University of Science and Technology, published in Phys. 133, 210803, further accelerating the development of practical multi-user quantum networks.
- The laboratory, established in 1984 and currently staffed by approximately 86 people, continues to investigate quantum phenomena in solid-state systems, with a focus on creating quantum devices for both computing and sensing applications; Yu Yang’s group previously reported long-range ZZ interaction via resonator-induced phase in superconducting qubits.
- Xiao-Song Ma achieved conference key rates of up to 7.54 bits per second with losses of 14.1 dB, utilizing a refined protocol and demonstrating multi-photon interference.