And interestly, WeChat claims they don't store user messages, but Chinese police apparently has it. Any app, website or forum on which users can post comments must verify ID-linked phone numbers first.
Unfortunately, this is quickly coming to the West as well. I believe twitter, facebook, imgur, and gmail (and I'm sure I missed many others) all require phone number verification, and most countries require some sort of ID to get a phone number.
And I say this with the direct opposite intent of whataboutism - it's horrifying in China, and if we let it, it'll be just as horrifying here.
Encryption is either broken or its not. No one has broken modern strong encryption yet. Quantum computing as a threat to strong encryption is still purely theoretical. Also, you don’t need to use a quantum computer to break encryption when you hold the private keys, you just decode to plain text the normal way. This is exactly what they did
Just to add a bit to this thought: Recent news about RSA keys and prime factoring seems to all be written as if there is pretty much no reason left to use encryption. But as jtms alludes, these important discoveries do have an immediate impact on weak encryption, which should be understood to mean decades-old outdated technologies. As far as strong encryption goes, quantum computing is still seriously far off unless a new discovery comes around to improve the results considerably.
Compared to the human life cycle, quantum cryptography is at the "on the verge of speaking in coherent sentences, but still prone to smearing feces on the wall" age and stage. You can sense that they'll grow up to be quite smart, but there's a lot of learning to go before you can hope for a Junior Einstein.
Does it really matter if it is PSB who stores it? :)
Special police in every major city have a few hundred people whose full time job is to go through online correspondence. That's not even a secret.