Chat Control — Definition, legislative context and status of the proposalChat Control — Definition, legislative context and status of the proposal

No mass surveillance has ever stopped expanding. No backdoor has ever remained closed.

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There is a moment in the life of democracies when collective fear is codified into law. The proposed European Regulation known as Chat Control (formally, the Regulation for the Prevention and Detection of Child Sexual Abuse — CSAR) represents perhaps the highest point of tension between two principles that the EU had sought to keep compatible: child protection and communications privacy.

Definition

Chat Control is a legislative initiative of the European Commission, originally presented in May 2022, that aims to require messaging service providers (WhatsApp, Signal, Telegram, Messenger, iMessage, etc.) and content-sharing platforms to detect, report and remove child sexual abuse material (CSAM) on their platforms.

The core of the controversy lies in the method: the Commission proposes that platforms implement automated detection systems that analyze both content and communications (private messages, photos, videos) to identify suspicious material. This necessarily implies inspecting the content of communications that are currently protected by end-to-end encryption (E2EE).

The legislative journey

May 2022:      Original proposal from the European Commission
               (scanning obligation for all providers)
Nov 2022:      EDPB Opinion (European Data Protection Supervisor)
               — serious doubts about compatibility with Art. 7 and 8 of the EU Charter
Feb 2023:      Council position — progress on the proposal with amendments
Jun 2023:      European Parliament (LIBE) opinion — critical amendments
               attempting to preserve encryption
Oct 2023:      Trilogue negotiations — deadlock
2024:          Belgian presidency attempts to unblock — no consensus
2025-2026:     Multiple rounds of negotiation. Several Member States block.
               The proposal remains unapproved.

The process has been unusually long and contentious. The original proposal required qualified majority in the Council and codecision with the European Parliament, which has led to a tug-of-war that has now lasted more than four years.

The positions on the board

In favor (with nuances)

Against (with nuances)

The core of the technical problem

The crux of the dispute is not philosophical but mathematical. The proposal requires platforms to detect CSAM in encrypted communications. The problem is formalized as follows:

Given an encrypted message $C = E_{k}(M)$ where:

• $E$ is an end-to-end encryption scheme
• $k$ is a key that only the sender and receiver possess
• $M$ is the content of the message

The platform is required to determine whether $M \in \mathcal{B}$ (where $\mathcal{B}$ is the set of known or classifiable CSAM content) without possessing $k$ and without weakening $E$ for all other users.

Cryptographers have repeatedly demonstrated that no scheme exists that simultaneously satisfies:

1. Security: the attacker (or the government that coerces it) cannot exploit the mechanism to read arbitrary messages
2. Accuracy: detection has acceptable false positive and false negative rates
3. Scalability: works for millions of messages per minute
4. Privacy: does not leak information about non-suspicious users

The impossibility is not technological in the sense of "we haven't invented it yet." It is structural: the properties of a secure encryption scheme imply that whoever does not have the key cannot determine any function of the content. Any exception to this is, by definition, a weakening of the encryption.

Current status

As of July 2026, the CSAR proposal remains under negotiation. It has not been approved nor withdrawn. The rotating presidencies of the Council have attempted multiple compromise texts that narrow the scope of scanning (limiting it to certain types of content, or to suspicious users, or requiring judicial oversight), but no version has achieved the necessary consensus.

The main obstacle remains the same: how to detect illegal content in encrypted communications without breaking encryption for everyone. And the answer, which cryptographers have been repeating since 2022, remains the same: it cannot be done.

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Related documents:

• Cifrado y vigilancia — Why mass scanning breaks E2EE
• Criptografía homomórfica — Promises and limits
• Pruebas de conocimiento cero — Applications to the detection problem
• Alternativas al escaneo masivo