Researchers say there is a way to make Bitcoin quantum safe without the need for a fork

Bitcoin transactions could be made quantum-resistant in the future Attacks Without changing the underlying protocol of the network, according to a suggestion from StarkWare researcher Avihu Mordechai Levy.

In a recently In a paper, Levy describes a “quantum safe Bitcoin” transaction system designed to remain secure even if quantum computers break the elliptic curve cryptography used today. The method works inside Bitcoin Existing scripting rules and will not require a soft fork or other network upgrade.

“We present QSB, a quantum-secure Bitcoin transaction system that requires no changes to the Bitcoin protocol and remains secure even in the presence of Shor’s algorithm,” Levy wrote.

The proposal replaces elliptic curve signatures with hash-based cryptography and Lamport signatures, an early signature scheme considered resistant to quantum attacks.

“since Lamport signatures “It is post-quantum secure, predicting a strong transaction identifier, as it is not possible to modify the transaction without producing a new Lamport signature — which an attacker cannot forge, even with quantum computing capabilities,” Levy wrote.

At the center of the design is a cryptographic puzzle that must be solved before the transaction can be broadcast. The paper estimates that finding a valid solution would require about 70 trillion attempts.

Unlike Bitcoin mining, the calculation process takes place before the transaction reaches the network. Users perform the work off-chain and send a transaction that already includes proof of the solution to the puzzle.

Levy estimates that the puzzle could be solved using commodity hardware such as GPUs at a cost of a few hundred dollars per transaction.

The scheme is designed to work within Bitcoin’s scripting limits of 201 opcodes and 10,000 bytes. The paper notes that these limits are too restrictive because each opcode counts toward the total, even if it appears in an unused body branch.

To fit within these limits, the system combines Lamport signatures and hash-based puzzles into a multi-layered transaction structure. It also offers “transaction pinning,” which requires anyone trying to modify the transaction to solve the puzzle again.

Levy describes the system as a “last resort” measure rather than a scalable fix. The paper says that the off-chain computational cost and on-chain transaction volume will not match Bitcoin’s target throughput or the needs of most users.

Transaction generation is also more complex than standard Bitcoin usage, and may be considered non-standard under current relay policies, meaning they may have issues with propagation and may need to be sent directly to mining pools rather than broadcast through the public memory pool.

The proposal also carries security Trade-offs. While it avoids attacks based on Shor’s algorithm that compromise elliptic curve signatures, Grover’s algorithm is still able to provide a quadratic speedup for quantum attackers.

“To the extent that the quantum threat is believed to be real, it remains necessary to continue ongoing efforts to research and implement the best possible solution for Bitcoin – one that is as efficient as possible, easy to use, and meets Bitcoin’s needs, through protocol-level changes,” Levy wrote.

Levy’s paper joins several proposals that have emerged showing how Bitcoin could transition to quantum-resistant cryptography, including Pep-360which introduces a Pay-to-Merkle-Root address format designed to support secure quantum signatures.

While the quantum threat to Bitcoin is still theoretical, companies including Google and Cloudflare They are already preparing for this, setting a deadline of 2029 to take their systems to the post-quantum stage.