Stacks Labs said it completed a post-quantum transfer of sBTC, the Bitcoin-backed token used on Stacks. Onchain records and deployed code show a successful withdrawal using a hash-based signature verifier.
The cited mainnet transaction moved 0.00001 sBTC from a vault contract to a recipient account on Oct. 15. Stacks announced the transfer on Nov. 11.
The result demonstrates a way to authorize withdrawals from a dedicated vault. It does not represent a quantum-security upgrade for existing sBTC balances or the Bitcoin backing them.
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View post on XHow the Vault Authorizes a Withdrawal
The transaction called the pq-vault contract’s sBTC withdrawal function and selected its lamport verifier. The deployed verifier code implements Lamport one-time signatures using SHA-256 hashes. Its instructions specify that each key must sign only one message digest.
The vault code provides public functions for opening a vault and depositing sBTC. A withdrawal signature binds the amount, recipient and next key, among other details. Anyone can submit a signed withdrawal, but the funds go to the recipient authorized by the signature. A successful withdrawal installs the next key.
This is a separate, opt-in contract path. Stacks’ signer documentation says sBTC’s Bitcoin backing is held in a Taproot address controlled by a threshold of signers. Adding hash-based authorization to a Stacks vault does not replace that Bitcoin-side spending mechanism or remove its exposure to a sufficiently powerful quantum computer. Bitcoin’s Schnorr signatures use elliptic-curve cryptography, unlike the vault’s hash-based authorization.
Stacks called the transaction the “first post-quantum sBTC transfer on Stacks mainnet,”, a claim specific to that token and network. It is not the first claim of a quantum-safe Bitcoin transaction: StarkWare announced a Bitcoin mainnet demonstration on Aug. 26, previously covered by The Defiant. That construction ran on Bitcoin itself, rather than transferring sBTC on Stacks.
Broader post-quantum security features in Stacks Labs’ upgrade vision through 2030, which calls for adopting new signature schemes through the network’s governance process.
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