alt Hacker NewsThe problem with that is if someone gets a hold of the logs from both the centralized service and the social media site they can compare timestamps and may be able to match them up.
Most people will be doing the whole process (site gives token, person gets token signed, person returns token) as quickly as possible which limits the candidates for a match. Worse, if the central service is compromised and wants to make it easier for log matching to identify people they could purposefully introduce delays which would make it easier to distinguish people.
Most people will use the same IP address through the verification process which would really make it easy.
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Just let people freely register as many virtual ids as possible (and confirm with the real id). Then use that virtual ids to register in actual services.
This allows anonymity, security (no timestamps comparison), freedom of speech and expression (to have independent accounts not linked to the main virtual id).
This is no different from VPN providers. Maybe have the central authority keep no logs just like VPN companies. We already have government agencies that do that for instance the agency that handles text to speech phone calls for deaf people. Alternatively use a VPN to sign the token.
Yes, timestamp comparison will be possible. I don't think there is a reasonable way around it? And authentication on to someone else is also unavoidable with reasonable privacy. I think a system with both of those drawbacks is still preferable to most other options.