Signal ships phone-number-free sign-up on Android beta, with ZK proofs unlinking the fee from accounts

Signal now lets Android users create an account without handing over a phone number, closing one of the longest-running privacy gaps in the most-used secure messenger. According to a technical write-up on dev.to, the feature arrived in the Signal Android 8.28.0 beta on 16 September 2026 as an optional, paid path to registration — and zero-knowledge proofs play a narrower role in it than much of the surrounding coverage suggests.

What actually shipped

A numberless account consists of two secrets: an Account ID and an Account Key, which Signal Android lead Greyson Parrelli described as "a username and password." No phone number is collected at any point in the flow, and nothing about the person behind the account is verified.

The feature is Android-only and still in beta. The dev.to write-up, which digests Signal's release notes and forum posts, reports that the 8.29 beta notes of 23 September 2026 kept phoneless registration in beta for another week of testing, that iOS release notes through 8.30.0 make no mention of it, and that Signal Desktop has no standalone registration at all.

The terms, as of 29 September 2026, are strict. Registration costs a one-time in-app purchase — 3 USD in the United States, with prices varying by country — and there is no recovery mechanism: lose the Account Key and the account is gone, and there is no PIN because the key replaces it. A username is optional, and without one Signal says the account is "completely unreachable" except in conversations it starts itself. Existing accounts cannot yet shed their phone number, though Signal says that may become possible later. Two-factor authentication via TOTP is available on the new accounts, with passkeys and hardware keys promised, and it is not yet offered on phone-number accounts.

Where the zero-knowledge proof fits

The cryptography is not what replaces the phone number — the Account ID and Key do that. The zero-knowledge proof exists so that Signal cannot connect the payment to the account it pays for. In a Signal Community forum post quoted by dev.to, Parrelli wrote that the purchase reuses the zero-knowledge proofs behind Signal's donation system, so that no link exists between a payment and an account. The machinery comes from the anonymous-credential code that powers donation badges, located in the zkgroup and zkcredential crates inside libsignal.

The abuse control, notably, is the fee rather than the math. Parrelli blamed spammers for the charge, warning that free accounts would let bad actors register in bulk and damage the network, and Signal has said it may raise the price if numberless accounts become a spam vector.

One gap remains. The only payment method today is a Play Store in-app purchase, which means Google still sees a Signal purchase on your Google account even though Signal itself cannot tie it to a Signal account. Signal says more payment methods are planned, and devices without Play Services cannot currently buy a numberless account at all.

Why it matters

Phone numbers are poor anchors for a private messaging app: they are bound to real-world identity through carriers, they can be ported or spoofed, and they hand a centralized third party leverage over who can register. Demand for number-free sign-up has been tracked in Signal's community forums since at least 2018, according to the dev.to analysis.

The deeper significance is the pattern: paid access to a service where the provider mathematically cannot learn which account paid. The same credential design generalizes to other problems — invite-only services, age or membership verification without stored birthdates, and rate limiting that does not track users — and Signal's zkgroup code is open source for anyone to study.

The write-up also cautions that zero-knowledge proofs are not a cure-all. Some proof systems require a trusted setup whose compromise would allow forged proofs, credentials can be stolen before they are blinded, circuit bugs can let invalid proofs verify, and metadata can leak even when the proof itself is sound. Signal's shift is real, but for now its trust model rests as much on a three-dollar fee and Google's payment rails as on the cryptography.