TechFlow News, April 12: According to a report by Decrypt, Avihu Mordechai Levy, a researcher at StarkWare, recently published a paper proposing a transaction scheme named “Quantum-Secure Bitcoin (QSB),” which enables Bitcoin transactions to resist quantum-computing attacks—without modifying the Bitcoin protocol, requiring no soft fork, or necessitating network upgrades.
The scheme replaces Bitcoin’s current elliptic-curve digital signature algorithm (ECDSA) with hash-based cryptography and Lamport signatures, which are considered resistant to Shor’s algorithm running on quantum computers. At its core lies an off-chain cryptographic puzzle that must be solved before broadcasting the transaction. The paper estimates that finding a valid solution requires approximately 70 trillion attempts—but this can be accomplished using consumer-grade hardware such as GPUs at a cost of several hundred dollars. The resulting solution is submitted alongside the transaction to the network. Additionally, the scheme introduces a “transaction pinning” mechanism, which forces any attacker attempting to alter the transaction to re-solve the puzzle.
Levy candidly acknowledges several limitations: both the off-chain computational cost and on-chain transaction size are incompatible with Bitcoin’s target throughput; the transaction creation process is more complex than standard operations and may be classified as a non-standard transaction, requiring direct submission to mining pools rather than broadcast via the public mempool; and Grover’s algorithm still grants quantum attackers a quadratic speedup advantage. Levy positions this scheme as a “last resort,” not a scalable long-term solution, and stresses the continued need for research and implementation of more robust quantum-resistant solutions at the protocol layer.
Currently, quantum threats to Bitcoin remain theoretical. However, companies including Google and Cloudflare have already begun preparations and have set a target of completing their post-quantum migration by 2029.
