Stacks Tests Post-Quantum Signatures With sBTC Transfer

Stacks has run what it calls the “first post-quantum sBTC transfer on Stacks mainnet,” using Lamport one-time signatures based on SHA-256 hashes.

The transaction called the pq-vault contract’s sBTC withdrawal function and selected its lamport verifier. The deployed code implements Lamport one-time signatures using SHA-256 hashes. Its instructions specify that a key must sign only one message digest.

How did the vault authorize the withdrawal?

The vault exposes public functions to open a vault and deposit sBTC. A withdrawal signature binds the amount, recipient and next key, among other details.

Anyone can submit the signed withdrawal. That does not give the submitter control of the funds. The money goes to the recipient authorized by the signature. After a successful withdrawal, the vault installs the next key.

The one-time rule limits each key to a single digest. The contract can therefore advance to the next key after a successful withdrawal, rather than leave one key eligible for repeated use.

The point is a controlled handover of signing authority within the Stacks contract, not a replacement for the signer system securing sBTC’s Bitcoin backing.

What does this change for sBTC users?

Nothing in the test removes the existing Bitcoin-side signer controls. Stacks’ signer documentation says sBTC’s backing sits in a Taproot address controlled by a threshold of signers.

Adding hash-based authorization to a Stacks vault does not replace that spending mechanism. Nor does it remove the backing’s exposure to a sufficiently powerful quantum computer. Bitcoin’s Schnorr signatures rely on elliptic-curve cryptography, rather than the vault’s hash-based authorization.

The transfer also remains separate from the standard sBTC process. It is an opt-in contract path, rather than a change to how the wider network secures Bitcoin assets.

The key distinction is where each control applies. The Lamport verifier checks authorization inside the Stacks contract. The threshold of signers controls spending from the Taproot address on Bitcoin. Adding one does not replace the other.

Is this the first quantum-safe Bitcoin transaction?

No, and the claim needs its precise scope. StarkWare announced a Bitcoin mainnet demonstration on Aug. 26, previously covered by The Defiant. That construction ran on Bitcoin itself. Stacks’ transaction transferred sBTC on Stacks, its own network.

That makes the two demonstrations different in location and mechanism. The earlier Bitcoin test did not transfer sBTC on Stacks, and the Stacks test did not change Bitcoin’s Taproot address controls.

The Aug. 26 announcement narrows the comparison. Both projects address post-quantum security, but they run on different networks and cover different assets.

Where does the broader plan go?

Post-quantum security sits inside Stacks Labs’ upgrade vision through 2030. The upgrade vision calls for adopting new signature schemes through the network’s governance process.

The 2030 horizon places the proposal in a long-term upgrade cycle. Governance provides the stated route for deciding which signature schemes the network adopts.

Governance remains a separate condition for any network-wide change. The test exercises one opt-in route, while the broader vision covers schemes across the network.

For users, the immediate effect is limited to an opt-in authorization route inside a Stacks vault. The test does not remove Bitcoin’s exposure to a sufficiently powerful quantum computer. The next structural step depends on governance. Any move from the opt-in contract path to broader signature adoption would require the network’s governance process.