European ‘chat control’ plans in the name of ‘child safety’ threaten end-to-end encryption



Are our online communications secure? Who has access to it? Sci-fi movies often explore a reality in which some sort of Big Brother system watches over our every move. However, it doesn’t represent the present realistically – not yet, anyway.

By using messaging services that encrypt our texts, images and videos from sender to recipient – end-to-end encryption – their content cannot be intercepted in transit. The keys needed to make sense of the encrypted data are stored only on devices communicating with each other, allowing only intended recipients to see the content. This sets aside revealing metadata, as well as the ability to hack users’ devices or access cloud storage which may include decrypted messages.

But the European Commission (EC) is currently preparing legislation intended to curb the dissemination of material of child sexual exploitation. the legislation – nicknamed “chat control” – will require the automatic search of all e-mails and personal messages of each citizen in search of suspicious content suspected in the context of the search for child pornography. Suspected cases will be reported to the police.

So far, only US communication services such as Facebook Messenger, Google Gmail or Microsoft Outlook voluntarily use such general surveillance. According to the Swiss Federal Police, in the vast majority of cases (86%) innocent citizens are suspected of having committed an offense due to the unreliable methods used. For example, harmless family beach photos or consensual sexting may be reported.

Yet the EC is investigating client-side analysis (CSS) as a possible method to filter even end-to-end encrypted messages for suspicious content. This would require the messaging app (WhatsApp or Signal, for example) to create a hash value (digital fingerprint) of the content to be sent, which would then be compared to a database of allegedly illegal content. If the algorithm reports a result, the message would not be sent and would be reported to law enforcement authorities.

Client side analysis

IT security experts caution against client-side scanning for several reasons.

First, to check whether the content flagged by the algorithm is indeed banned, a manual review should take place. This requires a technical functionality allowing third parties to verify the content of normally encrypted communications – a back door.

Backdoors fundamentally compromise end-to-end encryption security, as external adversaries such as intelligence agencies or hackers can find and abuse these vulnerabilities. Private correspondence – especially nude images – is also not safe in the hands of the provider or the authorities, as reports from misuse of intimate data by US agencies as good as large tech companies demonstrated.

More importantly, the scope of client-side scanning methods can easily be extended to filter match for for other purposes, such as targeted advertising, the sharing legitimate content or blocking of political communications.

Knowing that no court order would be required to authorize surveillance, citizens’ privacy would be in the hands of closed-source algorithms and hash databases controlled by global technology companies. Anyone controlling the hash database would be able to intercept any content of interest.

False positives

The scope of the proposed chat control legislation has already been extended beyond images and videos to search for text messages for possible attempts to ‘prepare children’. We can expect the false positive rate to be staggering.

A former judge of the European Court of Justice, Ninon Colneric, concluded that the proposed legislation on the control of the chat over the indiscriminate and permanent filtering of all private communications violate the fundamental rights of EU citizens. Yet the European Commission is determined to propose such legislation.

If the EU imposes backdoors in end-to-end encrypted email clients to search for suspicious content, it is just one more small step to impose such backdoors for law enforcement interception. . This would completely break end-to-end encryption and expose personal, business and state secrets to foreign intelligence agencies and hackers.

Destroying secure channels of communication would endanger whistleblowers and endanger the lives of dissidents in dictatorial regimes such as Hong Kong and Belarus. It is therefore not surprising that the ‘Five Eyes’ intelligence alliance pushes for cat control legislation in order to undermine the encryption.

Targeted police work

The protection of children is undoubtedly an urgent matter. However, this cannot and should not be done by sacrificing the secrecy of electronic communications. In fact, indiscriminate surveillance destroys safe spaces for victims of abuse to receive counseling and disproportionately targets minors themselves, while serious criminals continue to use self-exploiting end-to-end encrypted systems. .

The shutdown of the child pornography platform “Boystown” earlier this month demonstrated that targeted police work is essential to pursue the organized structures behind this horrific crime.

Instead of unleashing an unprecedented mass surveillance system on all of us, children must be better protected by educating the public, providing more therapy and support, and reducing the backlog of criminal investigators.


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