A researcher at the Israeli cryptography company StarkWare has successfully completed the first quantum-resistant Bitcoin transaction, preemptively protecting it from any future attacks using hypothetical quantum computers. Crucially, this didn’t require a soft-fork or any other change to the network’s consensus system. It just slotted right into the main ledger with additional security.
The problem of quantum computing on proof-of-work systems like Bitcoin has long been understood. While current computers would need an impossible amount of computing hardware to brute-force a cryptocurrency like Bitcoin, quantum computers could offer that power at a fraction of the cost. Protecting Bitcoin against this potential future is the subject of an ongoing debate, and no effective long-term solution has been agreed upon.
But right now, Bitcoin stored in many wallets with public-facing addresses is vulnerable. Gizmodo’s sources estimate that around 30% of the current Bitcoin supply is vulnerable to quantum computing attacks, potentially putting half a trillion dollars of crypto up for grabs to future attackers who get hold of this kind of hardware.
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In an example of how users might protect against that right now, the StarkWare researchers used a Quantum-Safe Bitcoin, or QSB, system. It uses a different cryptographic system from most Bitcoin transactions, built around hashing. Adding this secondary quantum-resistant lock makes it take much more quantum computing power to break it.
The transaction required substantial off-chain computing, with the transaction itself estimated to cost several hundred dollars worth of compute power. That makes this technique viable only for large-scale transactions worth many times more than that.
But it does secure Bitcoin against quantum attacks, potentially giving existing users an escape route should a quantum computing problem appear ahead of the decade-plus that many still see as the most likely timeline for such a threat.
This was an important step, showing that existing on-chain actions can secure transactions and Bitcoin wallets without the need to fork anything. A more permanent solution is required, but this is there if needed and provides a great jumping-off point for more research. Certainly, as computing power increases, the computing cost for this kind of secure transaction will reduce dramatically, too.