The connection between key and identity doesn't have to be public.
The point is that the headers of an email aren't encrypted (otherwise it couldn't be delivered). In the headers is who the message is to, who it's from, the subject, the time, and if you're lucky, the ip of the sender. All of that isn't encrypted and free for the taking and has nothing to do with the id attached to the key used to encrypt the content.
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The connection between key and identity doesn't have to be public.
The point is that the headers of an email aren't encrypted (otherwise it couldn't be delivered). In the headers is who the message is to, who it's from, the subject, the time, and if you're lucky, the ip of the sender. All of that isn't encrypted and free for the taking and has nothing to do with the id attached to the key used to encrypt the content.
Right, the metadata is always public.
Without strong encryption you have metadata that can be tied to an identity using statistics with enough data.
With strong encryption you have metadata that can be tied to a key and an identity using statistics with enough data.