Signal’s mission and sole focus is private communication. For years, Signal has kept your messages private, your profile information (like your name and profile photo) private, your contacts private, and your groups private – among much else. Now we’re taking that one step further, by making your...
It was the original purpose of the bitcoin algorithm to limit spam.
If you have to do a lot of maths that takes your computer (for example) 30 seconds, that means it costs 30 seconds of compute to create an account. Nothing to an average user, for a spammer that wants thousands of accounts it gets expensive.
Several captcha[0] libraries already use this and it's great for accessibility (normal captchas are terrible for it)
Because it's not. I can spin any number of emulators or VMs that do any amount of work with a simple script, but that's all it does. How does it prove I'm anything but a scripted, virtual instance of a person with a device?
There's a reason why Telegram is flooded with bots, Signal as of now has not been.