Signal has started rolling out Signal Login, an optional registration method that allows users to create a Signal account without providing a phone number. The feature will be rolled out first on Android and will come to iOS later.
As we previously reported, Signal Login is not a free alternative registration method. Signal requires users who choose to register without a phone number to make a one-time payment. The price at launch is $2.99 / € 3.49, although this may vary by region and currency.
Or the server(s), no? It’s trivially easy to archive, filter by account, and then decrypt if the one key has been found