Currently, the computational power of quantum computers is not sufficient to crack Bitcoin, primarily for the following reasons:
• Insufficient number of qubits: It is estimated that cracking Bitcoin's encryption technology requires at least 1,500 qubits to work continuously for 15 to 20 years. Currently, among publicly available quantum computers, Google's Willow chip has only 105 qubits, and the "Tianyan-504" developed by China Telecom Quantum and GuoDun Quantum has 504 qubits, which is still far from the required number for cracking.
• Algorithm limitations: Bitcoin uses the SHA-256 hash algorithm and the elliptic curve digital signature algorithm to ensure security. Although quantum computers have advantages in certain specific calculations, they still find it difficult to invert one-way hash functions. Current quantum algorithms, such as Grover's algorithm, cannot directly crack Bitcoin's hash and signature mechanisms.
• Quantum resistance of system design: Systems like Bitcoin only disclose the hash value of the public key before transactions, and the public key is only revealed after the transaction is broadcast. Quantum attackers must crack the key in a very short time, making the attack window brief and extremely challenging; for Bitcoin, the attack window is about 5 to 30 minutes, while Avalanche has only 1 second.
• Implementation of future defense solutions: Blockchain developers can introduce quantum-resistant cryptographic techniques through soft forks or hard forks. For example, Avalanche has submitted a request on GitHub to introduce quantum-resistant lattice encryption, and Bitcoin could also adopt hash-based Lamport signatures or quantum-resistant lattice encryption to upgrade its defenses.
