Craig Gidney, a Google Quantum AI researcher, has published a new study that suggests cracking popular RSA encryption would take 20 times less quantum resources than previously believed.
Bitcoin, and other cryptocurrencies were not specifically mentioned in the study; instead, it focused on the encryption techniques that serve as the technical foundation for safeguarding cryptocurrency wallets and, occasionally, transactions.
RSA is a public-key encryption method that can encrypt and decrypt data. It uses two separate but connected keys: a public key for encryption and a private key for decryption. Bitcoin does not employ RSA and instead relies on elliptic curve cryptography. However, ECC can be overcome by Shor's algorithm, a quantum method designed to factor huge numbers or solve logarithm issues, which is at the heart of public key cryptography.
ECC is a method of locking and unlocking digital data that uses mathematical calculations known as curves (which compute only in one direction) rather than large integers. Consider it a smaller key that has the same strength as a larger one. While 256-bit ECC keys are much more secure than 2048-bit RSA keys, quantum risks scale nonlinearly, and research like Gidney's shrinks the period by which such assaults become feasible.
“I estimate that a 2048-bit RSA integer could be factored in under a week by a quantum computer with fewer than one million noisy qubits,” Gidney explained. This was a stark revision from his 2019 article, which projected such a feat would take 20 million qubits and eight hours.
To be clear, no such machine exists yet. Condor, IBM's most powerful quantum processor to date, contains little over 1,100 qubits, while Google's Sycamore has 53. Quantum computing applies quantum mechanics concepts by replacing standard bits with quantum bits, or qubits.
Unlike bits, which can only represent 0 or 1, qubits can represent both 0 and 1 at the same time due to quantum phenomena such as superposition and entanglement. This enables quantum computers to execute several calculations concurrently, potentially solving issues that are now unsolvable for classical computers.
"This is a 20-fold decrease in the number of qubits from our previous estimate,” Gidney added.
A 20x increase in quantum cost estimation efficiency for RSA might be an indication of algorithmic patterns that eventually extend to ECC. RSA is still commonly employed in certificate authorities, TLS, and email encryption—all of which are essential components of the infrastructure that crypto often relies on.
