Over 500 of the world’s leading cryptographers, security researchers, and scientists from 34 countries have today delivered a devastating verdict on the EU’s proposed “Chat Control” regulation. An open letter published this morning declares the plan to mass-scan private messages is “technically infeasible,” a “danger to democracy,” and will “completely undermine” the security and privacy of all European citizens.

The scientific consensus comes just days before a crucial meeting of EU national experts on September 12 and weeks before a final vote planned for October 14. The letter massively increases pressure on a handful of undecided governments—notably Germany—whose votes will decide whether to form a blocking minority to stop the law.What is ‘Chat Control’?

The proposed EU regulation would legally require providers of services like WhatsApp, Signal, Instagram, E-Mail and others to scan all users’ private digital communications and chats—including text messages, photos, and videos. This automated, suspicionless scanning would apply even to end-to-end encrypted chats, forcing companies to bypass or break their own security protections. Any content flagged by the algorithms as potential child sexual abuse material (CSAM) would be automatically reported to authorities, effectively creating a system of constant mass surveillance for hundreds of millions of Europeans.

What the researchers highlight (key points)

The open letter from the scientific community systematically dismantles the core arguments for Chat Control, warning that the technology simply does not work and would create a surveillance infrastructure ripe for abuse:

• A Recipe for Error and False Accusations: The scientists state it is “simply not feasible” to scan hundreds of millions of users’ private photos and messages with “an acceptable level of accuracy.” This would trigger a tsunami of false reports, placing innocent citizens—families sharing holiday photos, teenagers in consensual relationships, even doctors exchanging medical images—under automatic suspicion.
• The End of Secure Encryption: The letter confirms that any form of scanning “inherently undermines the protections that end-to-end encryption is designed to guarantee.” It creates a backdoor on every phone and computer, a single point of failure that the scientists warn will become a “high-value target for threat actors.”
• A Gift to Criminals, a Threat to the Innocent: Researchers confirm that detection algorithms are “easy to evade” by perpetrators with trivial technical modifications. The surveillance system would therefore fail to catch criminals while subjecting the entire population to invasive, error-prone scanning.
• A Blueprint for Authoritarianism: The letter issues a stark warning that the proposal will create “unprecedented capabilities for surveillance, control, and censorship” with an inherent risk of “function creep and abuse by less democratic regimes.”

The Political Battlefield: Undecided Nations Hold the Key

The future of digital privacy in Europe hangs in the balance, with EU member states deeply divided. A blocking minority requires rejection or abstention by at least four Member States representing more than 35% of the EU population. Based on current stances, the population threshold would be reached if Germany joined the “not in favour” group alongside the seven governments already not in favour.

• Pro-Surveillance Bloc (14): A coalition led by Denmark, Ireland, Spain, and Italy is pushing hard for the law. They are joined by Bulgaria, Croatia, Cyprus, France, Hungary, Latvia, Lithuania, Malta, Portugal, and Slovakia.
• The Resistance (7): A firm group of critics includes Austria, Belgium, the Czech Republic, Finland, Luxembourg, the Netherlands, and Poland.
• The Kingmakers (7): The deciding votes lie with Estonia, Germany, Greece, Romania, Slovenia, and Sweden. Germany’s position is pivotal. A ‘No’ vote or an abstention from Berlin would kill the bill.

Patrick Breyer, a digital rights advocate and former Member of the European Parliament for the Pirate Party, urges the undecided governments to heed the scientific evidence:

“This letter is a final, unambiguous warning from the people who build and secure our digital world. They are screaming that this law is a technical and ethical disaster. Any minister who votes for this is willfully ignoring the unanimous advice of experts. The excuse that this can be done without breaking encryption is a lie, and the myth that exempting encrypted services would solve all problems has now been proven wrong.

I am calling on the government of Germany, in particular, to show political courage, but also on France to reconsider its stance. Do not sacrifice the fundamental rights of 500 million citizens for a security fantasy that will not protect a single child. The choice is simple: stand with the experts and defend a free and secure internet for all – including children, or stand with the surveillance hardliners and deploy authoritarian China-style methods. Europe is at a crossroads, and your vote will define its digital future.”

The Pirate Party and the scientific community advocate for investing in proven child protection measures, such as strengthening law enforcement’s targeted investigation capabilities, designing communications apps more securely, funding victim support and prevention programs, and promoting digital literacy, rather than pursuing dangerous mass surveillance technologies.

Suggested questions for competent national ministries:

• Encryption and national security: How will E2EE used by citizens, public authorities, businesses and critical services remain uncompromised under any detection mandates?
• Accuracy and efficacy: What evidence shows image/URL scanning can achieve low false‑positive/negative rates at EU scale and resist trivial evasion? The German Federal Crime agency has reported an error rate of 48% in 2024 (page 18).
• Scope and function creep: How does the government intend to ensure detection cannot be expanded or repurposed to broader surveillance/censorship in future (e.g., text/audio, political content)?
• Child protection outcomes: Which evidence‑based measures (education, digital literacy, trauma‑informed victim support, faster handling of voluntary reports, targeted investigations) will be prioritised?

Key quotes from the open letter:

• “On‑device detection, regardless of its technical implementation, inherently undermines the protections that end‑to‑end encryption is designed to guarantee.”
• “Existing research confirms that state‑of‑the‑art detectors would yield unacceptably high false positive and false negative rates, making them unsuitable for large‑scale detection campaigns at the scale of hundreds of millions of users.”
• “There is no machine‑learning algorithm that can [detect unknown CSAM] without committing a large number of errors … and all known algorithms are fundamentally susceptible to evasion.”

Further Information:

• Open Letter from 500+ Scientists (9 Sept 2025): csa-scientist-open-letter.org/…
• Map of National Positions and background information: www.chatcontrol.eu

Upcoming Dates:

• 12 September 2025: Council working party meeting on the proposal.
• 14 October 2025: Planned final vote by EU home affairs ministers.

patrick-breyer.de/en/danger-to…