Signal's No-Phone Registration Still Runs Through Google

Everyone's celebrating the headline: registration without a phone number on Signal will use zero-knowledge proofs. It hit 125+ points on Hacker News yesterday. I did what HN commenters rarely do — I read the commit. Here's what nobody else is saying: the anti-spam gate on anonymous registration routes through Google Play Billing.

The receipts

Commit 7da3357b564b landed in signalapp/Signal-Android on September 4, titled "Add ability to pay for a signal login." It introduces a stack of new classes — OneTimeProduct, OneTimePurchaseApi, OneTimePurchaseResult — and one detail that matters more than all the ZK math: the purchase path is gated by Environment.supportsGooglePlayBilling(), which returns true only when the build ID matches GOOGLE_PLAY_BILLING_APPLICATION_ID. The commit diff itself documents pricing "as reported by Google Play," keyed to the user's Play account. Signal's own community forum thread — ten pages and counting — confirms the shape of it: ZK proofs verify you paid, Play Billing is how you pay.

Why it matters

A zero-knowledge proof that your payment didn't link to your identity is worth exactly zero if the payment rail is Google. Play Billing means a Google account, a payment instrument, and a purchase record sitting in Mountain View's ledger — the ZK layer hides the link from Signal's servers, not from the platform holding the receipt. One privacy invader is swapped for a bigger one. The same HN thread makes the secondary point well: Signal's push notifications still ride on Google/Apple services on stock clients, so the phone-number removal fixes one metadata leak while the plumbing still phones home.

Verdict: real progress, honestly shipped — but "no phone number" is not "anonymous." Watch whether Signal ships a non-Play payment path before declaring this solved. If the coupon can only be bought from Google, the escape hatch has a toll booth on it.