A transaction using the Quantum-Safe Bitcoin (QSB) method has been confirmed on the Bitcoin mainnet. StarkWare stated that this is the first time the scheme has been verified on the mainnet without modifying Bitcoin’s consensus rules or requiring a soft fork.
This on-chain event is more like a demonstration of technical feasibility. It shows that existing Bitcoin rules can accommodate this type of transaction structure, but it does not mean the Bitcoin network as a whole is currently quantum-resistant.
Go on-chain without changing consensus rules
Traditional Bitcoin transactions rely on elliptic curve signatures. Theoretically, if sufficiently powerful fault-tolerant quantum computers emerge in the future, attackers could use Shor's algorithm to derive private keys from publicly exposed public keys.
QSB aims to shift the security foundation from elliptic curves to hash functions. According to StarkWare and researcher Avihu Levy, this approach enables transaction verification within the existing ECDSA verification framework by leveraging hash commitments and specific signature constructions, eliminating the need for new opcodes or node upgrades.
Higher generation cost
However, this type of transaction is not suitable for everyday use, as significant off-chain computations are required to find suitable transaction parameters before each QSB transaction is generated.
Research indicates that the off-chain cloud GPU computation cost for a single QSB expenditure is approximately between $75 and $150, with some estimates extending up to $200. This cost does not include on-chain Bitcoin miner fees, and must be recalculated for each transaction.
In addition, QSB transactions do not comply with Bitcoin's standard relay policy and are typically not propagated through the public mempool; they must be submitted directly to miners willing to include them. The first mainnet transaction was delivered to miners via MARA's Slipstream service.
Still cannot cover all Bitcoin scenarios
This transaction being confirmed only proves that the current Bitcoin consensus accepts the QSB structure; it does not mean that all addresses, wallets, or existing funds have received quantum-resistant protection.
According to the current design, QSB is primarily intended for traditional pre-SegWit script outputs and cannot directly protect Taproot outputs or cover Lightning Network channels. More importantly, funds must first be transferred into a QSB output via a standard transaction before they receive this type of hash protection.
This means that if the public key was already exposed before the transfer, and a quantum attacker has the capability at that time, the funds could still be compromised before confirmation. Addresses whose public keys have previously been revealed due to prior spending are also not directly protected by QSB.
Protocol-level solutions are still under research.
Researchers describe QSB as a "last resort" rather than a scalable alternative to ordinary Bitcoin transactions, as its computational cost, script size, and reliance on miner direct connectivity limit its practical applicability.
Currently, developers are also discussing longer-term protocol-level upgrades, such as BIP-360. This proposal aims to reduce Bitcoin’s long-term exposure to quantum attacks through a new output design. Unlike QSB, implementing such solutions requires changes to the Bitcoin protocol.
Next, external attention will focus on an independent review of the QSB code, additional mainnet testing, and the development of a more scalable post-quantum signature scheme. At this stage, this transaction is better viewed as a validation of a contingency path rather than a signal that Bitcoin’s quantum resistance has been fully achieved.