A new development in the realm of cryptocurrency was unveiled recently, addressing the growing concerns surrounding quantum computing threats to Bitcoin transactions. Avihu Levy, the Chief Product Officer at StarkWare, has introduced an innovative open-source project named Quantum Safe Bitcoin (QSB), which aims to fortify Bitcoin transactions against potential quantum attacks without the need for any alterations to the existing network protocol.
Released on April 9, QSB cleverly utilizes Bitcoin’s current consensus rules, effectively ensuring that no soft fork, protocol upgrade, or community coordination is required for implementation. This approach operates within Bitcoin’s legacy Script limitations, adhering to the constraints of 201 opcodes and a 10,000-byte limit. Notably, it achieves approximately 118 bits of security against Shor’s algorithm, which is a quantum computing attack capable of undermining the conventional security model of Bitcoin transactions.
Central to the QSB project is the replacement of Bitcoin’s traditional elliptic-curve digital signature algorithm (ECDSA) with a hash-based construction. This modification allows quantum computers to only engage Grover’s algorithm for attacks, which presents a significantly lower threat level compared to direct attacks, offering a quadratic speedup rather than an outright breach. However, the proposed method does come at a high operational cost, as off-chain computation for a single transaction could range from $75 to $150 in cloud GPU time. Importantly, the GPU computations are publicly verifiable, ensuring that private keys never leave the user’s device, thereby maintaining a level of security during the transaction process.
The announcement coincided with heightened speculation regarding the potential capabilities of quantum computers in compromising Bitcoin’s security. A recent publication from Google Quantum AI raised alarms by suggesting that under certain conditions, breaking Bitcoin’s elliptic-curve cryptography could necessitate fewer than 500,000 physical qubits, a drastic reduction compared to previous estimates. According to the research, a sufficiently powerful quantum machine could derive a private key from an exposed public key in roughly nine minutes, a timeframe alarming close to Bitcoin’s existing 10-minute block interval.
While QSB marks a significant step forward, it is essential to note that the project remains in its development phase. Initial tests involving the GPU pinning mechanism have been conducted successfully over approximately six hours across a cluster of eight Nvidia RTX PRO 6000 GPUs. However, the end-to-end processes of digest search and on-chain broadcast have yet to be finalized. Additionally, transactions utilizing QSB exceed the default relay policy limits, necessitating a direct submission to miners through platforms such as Marathon’s Slipstream.
Levy has characterized QSB as a valuable tool for extreme circumstances rather than a standard operational replacement for everyday Bitcoin transactions. Nonetheless, the initiative signifies a promising advancement, illustrating a feasible route to enhance Bitcoin’s security against the looming quantum computing menace while remaining firmly rooted in the established framework of the network.
