I have helped a little with some ongoing research on the subject of client-side-scanning in a European research center. Only some low level stuff, but I possess a solid background in IT security and I can explain a little what the proposition made to the EU is. I am by no means condemning what is proposed here.I myself based on what experts have explained am against the whole idea because of the slippery slope it creates for authoritarian government and how easily it can be abused.

The idea is to use perceptual hashing to create a local or remote database of known abuse material (Basically creating an approximation of already known CP content and hashing it) and then comparing all images accessible to the messaging app against this database by using the same perceptual hashing process on them.

It's called Client-Side-Scanning because of the fact that it's simply circumventing the encryption process. Circumvention in this case means that the process happens outside of the communication protocol, either before or after the images, media, etc, are sent. It does not matter that you use end-to-end encryption if the scanning is happening on you data at rest on your device and not in transit. In this sense it wouldn't directly have an adverse effect on end-to-end encryption.

Some of the most obvious issues with this idea, outside of the blatant privacy violation are:

1. Performance: how big is the database going to get? Do we ever stop including stuff?
2. Ethical: Who is responsible for including hashes in the database? Once a hash is in there it's probably impossible to tell what it represent, this can obviously be abused by unscrupulous governments.
3. Personal: There is heavy social stigma associated with CP and child abuse. Because of how they work, perceptual hashes are going to create false positives. How are these false positives going to be addressed by the authorities? Because when the police come knocking on your door looking for CP, your neighbors might not care or understand that it was a false positive.
4. False positives: the false positive rate for single hashes is going to stay roughly the same but the bigger the database gets the more false positive there is going to be. This will quickly lead to problems managing false positive.
5. Authorities: Local Authorities are generally stretcht thin and have limited resources. Who is going to deal with the influx of reports coming from this system?

People in Reddit and sometimes here always praise the EU as some bastion of privacy, and I always got downvoted when I said that this isn't always true. And now here we are. I hope people don't forget this after a month, like they always do.

citizens have the right to private communication.

What is wrong with the eu? Why do they need to always ban end to end encryption?

So for, here is what I can tell from specific countries:

On board with privacy destroying law:

Spain, Hungary, Cyprus

Mostly on board: (support on device scanning but not weakening E2EE)

Ireland, Denmark

Against:

Finland, Germany

Feel free to update this if you know more.

Source: https://www.wired.com/story/europe-break-encryption-leaked-document-csa-law/

And the EU is wondering why they're having an image problem

Making it illegal only hampers those that follow the law.

Criminals, by definition, already don't follow the law.

While this would be terrible if it passes, a part of me hopes a silver lining would be a massive surge in open source development focusing on privacy respecting software that does not follow or enable this disgusting behavior by the eu

This is almost definitely not going through the ECJ. If they pass this directive I'm gonna take my chances.

Thanks to the Matrix protocol there is no chance of getting rid of E2EE communication anyway. There is no feasible way to stop decentralized communication like that, no without killing the internet.

Just imagine the headline we'd see in the west if this was happening in China.

If apps would turn off e2e encryption, how would it be? Would it affect bordering regions? Users of VPNs inside EU?

My country proposed a ban on VPN software (targeting appstores providibg them), it can also target messengers. If I get a EU version of this app, or if I use a european VPN to connect via it, would I be less safe sending political memes?

I wonder if openPGP will ever gain popularity.

The only ones I have seen that even publish a key for me to use are a few famous internet individuals (people like Richard stallman, (I don't know if he specifically uses it)), a few companies like mullvad, a few orgs like EFF, whistleblowers, and a few governmental organisations like the Financial Supervisory Authority in my country.

I wonder if projects like Signal could make a community run and certified hash database that could be included in Signal et al without threat of governments and self-interested actors putting malicious entries in. It definitely doesn't solve every problem with the client side scanning, but it does solve some.

But... an open, verifiable database of CSAM hashes has its own serious problems :-S Maybe an open, audited AI tool that in turn makes the database? Perhaps there's some clever trick to make it verifiable that all the hashes are for CSAM without requiring extra people to audit the CSAM itself.

@makeasnek
Imagine a data leak in such a situation.

Although some US corporations such as Meta are already scanning European messages for previously classified CSAM ‚only‘

This is news to me, does anyone have any more detail?

If they can scan it, they can edit it.

Can this be circumvented somehow? And how would apps with end to end encryption work if a person in a non-EU state spoke to someone inside the EU?

Terrorists will have no problem writing their own encryption program, and more ordinary citizens will install malicious apps from unofficial app stores.