Beeper will know only a small number of valid serial numbers

If it ever becomes popular, there will be a lot of duplicate serial numbers. That's easy to detect and ban.

Not if they require a certificate containing the serial number/imei/... + a nonce provided by Apple, signed with a private key/certificate stored in the secured enclave, loaded into the device when it's manufactured.

The GP comment was:

> Apple can break Beeper without relying on the secure enclave: If Apple devices just send their serial number

You have come full circle with the comment 4 posts up.