This is cryptography 101. Asymmetric crypto lets you encrypt a message using a public key without having the private key to decrypt it.

Remember that the encryption is being done client side by apps these networks control. E2E is therefore sort of fake to begin with because WhatsApp is not only the servers but also the client. You can't mix and match, so you have to encrypt messages using software provided to you by the "adversary". E2E encryption is therefore more of a tool to control bad insiders and negotiate with governments than encryption as conventionally understood.

Also remember that tech firms run the public key directory. Almost nobody verifies public keys, and even if they did, they're doing so with apps controlled by the tech firms so you can't know the verification is done properly anyway. And the keys can change at any moment, with your own way to know it's happened being UI controlled by the tech firms.

Still, even if clients and servers were separate, nothing stops clients from encrypting messages using a well known government public key and attaching that along with the e2e encrypted version.

The point the parent was making is that if Apple decided tomorrow they wanted to implement a backdoor for law enforcement there's no way we'd know until the evidence starts to show up in court cases (or someone at Apple/LEO leaks the knowledge). The system is a closed loop and proprietary. We're taking their word for it.

But nothing stops the clients lying and putting fake mundane plaintext in the government "copy"

Not the government's problem to solve, and tech firms can easily solve that by changing how their encryption works (e.g. using secure enclaves, or remote attestation).

That does not change anything, asymmetric or symmetric, the same principles apply. E2E means that only the recipients has the ability to decrypt the messages, so far we seem to agree. As I said, and you verified, for your scheme to work, then messages should be encrypted with a known government PK, but that is not privacy. Now the government has the ability to decrypt everything, and can store messages indefinitely and use it for whatever they decide now and in the future. That is a surveillance state by definition.

> If a company have the means to decrypt a particular users data, they have the ability to decrypt all users data.

The messaging company can embed the police's encryption key in the app but not have possession of the corresponding decryption key.

> exceptions to privacy have always led to a slippery slope

That's a reasonable argument. But to the GP's point, thats not a technical argument. Its just another argument that the policy is bad for normal "bad policy" reasons. It has nothing to do with the math.

> The messaging company can embed the police's encryption key in the app but not have possession of the corresponding decryption key.

Once three people have access to a secret, it isn’t secret anymore. Once hundreds of thousands of police officers have access to the private key, it will leak, and everyone will be able to read these messages.

> it will leak, and everyone will be able to read these messages.

Again, do you see how this is not a technical argument? It might be a good argument. But its not an argument about the math or the computer science. "We can't trust the police" is a social argument, not a technical argument. A math or CS degree will not help you understand this argument.

Anyway, why would the decryption key be in the hands of "hundreds of thousands of police officers"? Especially when the decryption key itself is useless without access to the encrypted messages themselves. If this were implemented, its much more likely that the police would build themselves a web portal or something through which they could access people's WhatsApp messaging logs. The crypto could all be handled on the data portal backend.

A much stronger argument against this sort of thing is the governmental slippery slope argument. If the UK police gains capabilities like this, you bet every other country will (reasonably) demand similar access. Apple / Meta would have to decide which police / security departments to work with, and thats a very complex problem. Who do you trust? Hungary? Bulgaria? Russia? Iran? Egypt? China? Brazil? Where, exactly, is the line? And should access be revoked after a coup, like in Niger?

Its much easier to just refuse all governmental cooperation. It protects your brand. And makes it much simpler to justify refusing access to police departments who you don't trust.

"This security scheme wouldn't work because of these social factors" _is_ a technical argument. Security is very specifically about making sure the right people have access to a resource and the wrong people don't. Social aspects are inherent in this. Therefore, in the context of security, social arguments are technical arguments.

Arguing that the myriad local police departments of the United States in particular do not have the security posture required to keep access to a data portal secure is a technical argument against government-backdoor encryption.

The article describes “type 3” bad ideas like demands to work out new mathematics:

> “Work it out” is generally a demand to invent new mathematics, but sadly, mathematics doesn’t work like that.

E2E + a backdoor for a particular police department isn’t the sort of bad idea that requires new mathematics.

The example is

> For the last 25 years, engineers have said ‘we can make it secure, or we can let law enforcement have access, but that means the Chinese can get in too” and politicians reply “no, make secure but not for people we like”.

Insecure police departments will inevitably leak the backdoor keys. It's not possible to limit who can use decryption keys based on who they are and not just possession of the keys under our current understanding of how encryption works. If you assume that the police will never leak keys then sure it's easy. But arguing about whether or not social factors like police department computer security is good enough to safely store keys is a technical argument about this technical problem.

Thanks for trying so hard here.

It's quite depressing how many people here don't seem able to deconflate "I don't believe police can be trusted with this power" from "it is mathematically impossible to give it to them".

This is a nice clear example of how experts talk themselves into lying to the public for the greater good, as we saw so often in the past :(

> Btw, end-to-end encryption by its very definition, means that only the sender and receiver kan decrypt it. Your scheme is basically saying that the police should also be a receiver of all messages...

And serverless literally means "without servers", and yet...

Point being, scope is a free variable. "E2EE" that's managed by a central server is already stretching it, yet people accept it. They'll mostly accept excluding law enforcement out of the scope of eavesdropers "E2EE" protects you from too.

Centrally managed E2EE is not end to end if the server can decrypt anything. The definition means that the keys to decrypt only exists at either end.