A breakthrough in protecting cryptocurrency from a potential attack by a quantum computer has been announced by a cryptography and blockchain-infrastructure company.
Israel-based StarkWare revealed Aug. 26 that a quantum-safe transaction using its Quantum-Safe Bitcoin (QSB) method had been mined on the Bitcoin (BTC) mainnet, the cryptocurrency’s live production network.
"StarkWare’s announcement is significant because it demonstrates something that, until now, many people assumed would require a change to the Bitcoin protocol," explained David de Paula Santos Silva, founder and CEO of CyberX , a global cybersecurity company.
"A Bitcoin holder can now move coins into a quantum-resistant construction using Bitcoin as it exists today, without changing its consensus rules," he told TechNewsWorld.
He cautioned, however, that StarkWare's QSB method, developed by the company's general manager of applications, Avihu Levy, does not make Bitcoin itself quantum-safe. "What was demonstrated on mainnet is a specific way of protecting particular holdings against a quantum adversary," he said.
"As far as we are aware, this is the first time anyone has actually done this on mainnet instead of just writing a paper about it," added Joni Zhuleku, chief research officer at Altcoin Pro , a cryptocurrency education and coaching company in Tampa, Fla.
"For holders, that matters because quantum used to be a someday problem, and now there's a real, working way to protect coins if someone wants to use it today," he told TechNewsWorld.
"Most people won't need to touch this yet," he said, "but it proves the defense doesn't have to wait on Bitcoin itself changing first because reaching consensus on Bitcoin takes a long time among miners."
StarkWare explained that Bitcoin’s signatures rest on elliptic curve cryptography. Shor’s algorithm, running on a large enough quantum computer, will be able to solve that class of mathematical problem quickly, so the puzzle protecting a coin will no longer be sufficient to protect it.
QSB closes the window for that type of attack by adding a second quantum-resistant lock alongside the existing one, built on hash functions instead of elliptic curves, StarkWare explained. Shor’s algorithm does not pose the same threat to hash functions as it does to elliptic-curve cryptography.
It noted that QSB uses signature grinding, a technique that lets a valid Bitcoin signature be created without a private key, and it works on Bitcoin exactly as it exists today. The sender spends computational effort searching for a spending transaction whose hash happens to be a validly formatted signature.
Bitcoin accepts it, and the transaction’s security then depends on the difficulty of reversing a hash rather than the secrecy of a private key, it added. The computational work is performed off-chain before the transaction is broadcast.
Private keys are paired with public keys. Publishing a public key is safe today because existing computers cannot feasibly work backward from it to recover the private key. A sufficiently powerful quantum computer running Shor’s algorithm could change that. As StarkWare put it, every published public key would then become "a private key waiting to be recovered."
While QSB shows that BTC holders may have ways to gain some quantum-resistant protection before Bitcoin undergoes a full protocol upgrade, it is not a complete solution, maintained Florian Neukart, chief technology officer at Terra Quantum , a global q…