Quantum computer with 22,600 qubits announced

Alice & Bob has announced a quantum computer with 22,600 physical qubits that, in theory, could break a 2048-bit RSA key in just over three days. The company claims this represents a significant step forward in quantum computing capabilities, though it remains a theoretical estimate.

Technical challenges remain

Despite the announcement, several technical barriers must be overcome before such a quantum computer can be used effectively. Experts caution that large-scale practical applications of this technology are not imminent, and the transition from theory to real-world use is still uncertain.

Symmetric vs. asymmetric encryption

In cryptography, there are two main types of systems: symmetric encryption, which uses the same key for both encryption and decryption, and asymmetric encryption, which uses a private key for decryption and a public key for encryption. Quantum computers, particularly with the Shor algorithm, pose a significant threat to asymmetric encryption systems, especially those based on factorization or discrete logarithm problems.

RSA and its vulnerabilities

RSA is an asymmetric encryption algorithm widely used on the Internet and by banks. According to Eric Lu of Cognition, the cost of attacking a 1024-bit RSA key would be approximately $30 million, making it accessible to entities with large GPU fleets, such as those found in data centers. This cost refers to breaking a single key, not breaking RSA-1024 as a whole, and it does not involve quantum computing.

RSA key size recommendations

The ANSSI (National Cybersecurity Agency of France) recommends a minimum RSA key size of 2048 bits for use up to the end of 2030 and 3072 bits from 2031 onward. RSA 4096 is also commonly used. Alice & Bob's announcement highlights the estimated resources needed to run the Shor algorithm on a 2048-bit RSA key using their chat qubits: approximately 23,000 physical qubits and three days.

Debate over the announcement

Whether Alice & Bob's announcement represents a genuine scientific breakthrough or a marketing move remains a subject of debate. The startup is leveraging its chat qubits and their tolerance to failures. Additionally, Alice & Bob offers technical approaches that could reduce both the time and cost required to break RSA 2048, which is a notable development. However, the practical implications of these advancements are still under scrutiny.