China manipulates data pretty much anywhere imaginable. See the Google Maps link [1] and corresponding Baidu Maps [2] locations. Notice how the Google Maps data has huge disagreement between the road network and satellite imagery? It's because if you do mapping in China, the government hands you a perturbation function to apply to each data layer. You have to warp your data per their function, and they can audit it. Baidu doesn't have to do this. However, both Google and Baidu maps are WAY off on GPS locations, 100+ meters off, everybody has to do that unless yo have an accurate mapping license.
I realize this is a little off topic, but since I work on something which has a big China presence, I'm always running into their BS, and censorship is just one little piece of it. VPN connectivity to your non-China offices is also problematic, running TLS over the Chinese internet is also problematic, unless you use officially provided certs and keys, etc.
About this perturbation function: almost the entire world uses the WGS84 datum. The Chinese use a datum that's similar but subtly different. If you didn't account for this datum you got shifted roads and features. The technical information about this datum has never officially been made public, but only licensed to certain companies. I'm fairly certain Google doesn't have such a license. You can find reverse engineered info online but there's no guarantee that those are correct.
You're referring to GCJ-02. From best as I can figure, it adds some form multi-frequency noise to a shifted WGS84 coordinate, but it also seems that different companies are told to use different coefficients for the different noise frequencies, that's how they can tell if you're doing what you're told.
Regardless, it's difficult to work with. If you have a mapping license, you must also take serious precautions never to let the accurate map data leave China, or your Chinese employees are in deep trouble.
You cited the actual Signal app, but provided no citation that Signal works in China. Can you please provide evidence of that?
Furthermore, just because it works in China doesn't mean that it won't cause your encrypted traffic to get flagged. This is why the threat model for a sophisticated network adversary, like the Chinese government, is difficult to model against.
Obviously there's not a snowball's chance in hell that Open Whisper Systems would ever even consider complying with any demand from the PRC.
I just don't think PRC authorities really care about Signal. It's not popular, not available in the app stores available to the Chinese masses, and anyone using it is probably just going to tunnel out anyway. They tend to ban things that are competitive, and Signal just isn't. It's a niche app.
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I realize this is a little off topic, but since I work on something which has a big China presence, I'm always running into their BS, and censorship is just one little piece of it. VPN connectivity to your non-China offices is also problematic, running TLS over the Chinese internet is also problematic, unless you use officially provided certs and keys, etc.
[1] https://www.google.com/maps/place/Beijing,+China/@39.7616007... [2] https://map.baidu.com/@12957558.390456071,4804287.368277797,...