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Comment by Retr0id | Hacker News Reader

Signal uses the DRM APIs to mitigate threats like Microsoft Recall, but it doesn't stop the app itself from reading its own data.

I don't really see how it's possible to mitigate client compromise. You can decrypt stuff on a secure enclave but at some point the client has to pull it out and render it.

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> I don't really see how it's possible to mitigate client compromise

Easy: pass laws requiring chat providers to implement interoperability standards so that users can bring their own trusted clients. You're still at risk if your recipient is using a compromised client, but that's a problem that you have the power to solve, and it's much easier to convince someone to switch a secure client if they don't have to worry about losing their contacts.

You seem to think the government wants your messages to be private and would "pass laws" to this effect.

Methinks you put far too much faith in the government, at least from my understanding of the history of cybersecurity :)

Information should certainly be kept confidential, but Chat Control is also necessary.Furthermore, the former is merely rigid laws and regulations, while the latter is used to prevent the Satanists, which is capable of committing all kinds of evil.

> Easy: pass laws requiring chat providers to implement interoperability standards so that users can bring their own trusted clients.

In Europe that's called the Digital Markets Act.

That's not permissionless afaik. "Users" can't really do it. It's frustrating that all these legislations appear to view it as a business problem rather than a private individual's right to communicate securely.

Right, I get what you mean.

But in a way, I feel like sometimes it makes sense to not completely open everything. Say a messaging app, it makes sense to not just make it free for all. As a company, if I let you interoperate with my servers that I pay and maintain, I guess it makes sense that I may want to check who you are before. I think?

We probably can't make it free for all, but for something like a messaging app, we also need to recognize that it isn't optional to function in society. It should be regulated more like a utility:

- Facebook can still control the identity, but there needs to be a legal recourse for getting banned, and their policies can't discriminate against viewpoints, for example

- The client specs should be open so that an alternate client can be implemented (sort of like how Telegram is currently)

Telegram isn't E2EE by default in the first place (and isn't E2EE for group messages at all).

I meant the platform openness aspect, that you are allowed to use alternate clients, but the identity is centralized E2EE is largely independent of this choice.

> but there needs to be a legal recourse for getting banned

Agreed.

> The client specs should be open so that an alternate client can be implemented

An example that comes to mind is Signal, where they don't want that. They get a lot of criticism for it of course, but I think it the reasoning actually makes sense: in terms of security, allowing third-party clients is a security risk. If your threat model is "people who risk their life using it", it makes sense, right?

Under the EU's Digital Markets Act, WhatsApp is considered a gatekeeper (Signal is not) and has to be open to interoperability. It seems like they do audit the implementations in order to make sure that the security is not too bad. Which makes sense again, but has a cost. For Meta, that's fine. For Signal... I don't know.

Also WhatsApp will - if I understand correctly - make it very clear that you are talking to someone on a third-party client (and again they get a lot of criticism for that). But I think it makes sense... If WhatsApp was so open that every second client was pretty much a spyware, that would defeat the purpose of E2EE messaging.

Not that I strongly disagree, but just saying that it seems... complicated.

I was intending that the alternate client should exist to function as an escape hatch. I fully expect most people will still use the default one, just like how people used the official reddit/telegram client when third party ones were available. The existence of an alternative constrains how much Facebook can enshittify the experience.

E2EE is about secure transport between the endpoints. What happens to the message after the endpoint is not something an app can feasibly enforce. Having control of the clients can at most do things like enforcing deletes, which IMO is not a good idea anyway.

> every second client was pretty much a spyware

Very few people will actually use one since the official app won't be outwardly too hostile, and those who do should be sufficiently discerning.

I don't think that it can work like that. If you make it fully open, you don't know what can happen. It cannot improve the security, it can only worsen it.

Suddenly you go from people using WhatsApp to people using random apps that you have no idea about, I think it's a step backward.

The "escape hatch", IMO, is an alternative messenger (like Signal). If Meta makes WhatsApp really bad, people can just switch to Signal. It's infinitely easier than moving away from AWS or the Microsoft Suite. The lock-in effect is really just that people can't be arsed to install it.

I think that the mere existence of Signal already forces Meta to keep WhatsApp relatively good. And to be fair, around me people like WhatsApp better because it has features they want and that Signal doesn't have.

>I don't really see how it's possible to mitigate client compromise.

You could of course offload plaintext input and output along with cryptographic operations and key management to separate devices that interact with the networked device unidirectionally over hardware data diodes, that prevent malware from getting in or getting the keys out.

Throw in some v3 Onion Services for p2p ciphertext routing, and decent ciphersuite and you've successfully made it to at least three watch lists just by reading this. Anyway, here's one I made earlier https://github.com/maqp/tfc

> don't really see how it's possible to mitigate client compromise.

Think of the way DRM'ed video is played. If the media player application is compromised, the video data is still secure. Thats because the GPU does both the decryption and rendering, and will not let the application read it back.

Video decryption+decoding is a well-defined enough problem that you can ship silicon that does it. You can't do the same thing for the UI of a social media app.

You could put the entire app within TrustZone, but then you're not trusting the app vendor any less than you were before.

Although now I think about it more, you could have APIs for "decrypt this [text/image] with key $id, and render it as a secure overlay at coordinates ($x, $y)"

Exactly. Thats how DRM video works, and I don't see why you couldn't do the same for text.

Actual DRM uses symmetric keys though, figuring out how to do the crypto in an E2EE-comaptible way would be challenging.

There will always, ALWAYS be the analog hole in security models like this.

It's pretty hard for the government or service provider to snoop through the analog hole unless they have a camera on your forehead...

That's not what signal's doing though. It's just asking the OS nicely to not capture screen contents. There are secure ways of doing media playback, but that's not what signal's using.

By avoiding untrustworthy clients. All Windows devices should be considered compromised after last year.

That's not mitigating client compromise, that's a whole other thing - trying to construct an uncompromiseable client.

You don't build defense-in-depth by assuming something can't be compromised.

Clients can always be compromised. I'm not talking about a client that can't be compromised, but simply a client that is not compromised out-of-the-box.

That seems orthogonal to the subject of this discussion, i.e. "Compromise of the client side application or OS shouldn't break the security model."

Why last year?

Windows recall, intrusive addition of AI features (is there even a pinky promise that they're not training on user data?), more builtin ads, and less user control (most notably the removal of using the OS without an account - something that makes sense in the context of undisclosed theft of private information).

This was 2025. I'm excited for what 2026 will bring. Things are moving fast indeed.

Windows has been sending usage history back to their servers for longer than just last year

This. The gap in E2E is the point at which I type in clear text and the point at which I read clear text. Those can be exploited.

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