In general the ledger of all transactions is public. But it’s like all of the transactions are tied to a random id. So to unmask a person you have to find at least one transaction that identifies the person tied to the id. So you can remain anonymous if you try really hard, but make one mistake and your whole history can be unraveled and known.

In general it is considerably easier to unmask people using crypto than other methods because perfect security is hard (criminals are dumb).