Fujitsu believes that RSA encryption will remain secure against quantum computers for the foreseeable future. The Japanese hardware manufacturer has carried out tests with its in-house quantum simulator. In the long term, however, a rethinking of cyber security must take place.
According to Fujitsu, concerns about the security of previously used cryptographic methods compared to quantum computers are growing. At the same time, nobody knows exactly how long the widespread RSA algorithm (Rivest-Shamir-Adleman) can withstand a decryption attempt using a quantum computer. That is why they wanted to provide clarity with their 39-qubit quantum simulator, presented in September 2022. The Shor algorithm was used, which has the potential to decrypt even complex, common encryption methods. Conclusions about more complex procedures could be drawn from the results of shorter key lengths.
The result: It would need a fully fault-tolerant, superconducting circuit-based quantum computer with around 10,000 qubits and 2.23 trillion quantum gates. Such a computer would still need 104 days to decrypt a 2048-bit RSA encryption. However, this completely fault-tolerant type of quantum computer does not yet exist. Even the largest planned processors have not yet reached the number of qubits.
No danger in the short term, yes in the long term
In the short term, there is no danger from quantum computers for the RSA method. Nevertheless, the Fujitsu researchers warn that they want to continue researching the consequences of more powerful quantum computers on the security of cryptography. “We must not become complacent,” said Tetsuya Izu, senior director of data & security research at Fujitsu in the release on the result. The world must prepare for the fact that quantum computers could one day fundamentally change general security thinking.
In 2023, Fujitsu would like to present its own physical 64 qubit computer. A factoring algorithm recently unveiled by Chinese researchers could outsmart RSA faster than the previous favourite, the Shor algorithm, also used by Fujitsu. However, experts doubt the potential.
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