Quantum computers may soon break blockchain cryptography: Report

According to a recent paper, Chinese researchers claimed to have discovered a new method to break the Rivest-Shamir-Adleman 2048-bit (RSA-2048) signature algorithm found in blockchains and other security protocols. RSA is a cryptographic technique that uses a public key to encrypt information and a private key to decrypt it.

Breaking the RSA-2048 algorithm, like other algorithms in the RSA family of numbers, requires finding the prime factors of a number with 617 decimal digits and 2048 binary digits. Experts estimate that it would take ordinary computers 300 trillion years to break an RSA-2048 encryption key. However, Chinese researchers said in their paper that the encryption could be inverted using a quantum computer with 372 qubits, or a fundamental unit of information that acts as a proxy for computational power.

By comparison, the latest IBM Osprey quantum computer has a processing capacity of 433 qubits. Previously, experts calculated that factoring RSA-2048 with quantum computers using Shor’s algorithm (a quantum factoring method) would require 13,436 qubits.

Unlike classical computers that operate on a binary basis of 0 or 1, quantum computers use quantum bits that can take on infinite states at temperatures of −273 °C (−459.4 °F), achieved by using liquid gas coolants. Thus, the quantum computer is able to map all possible solutions to a cryptographic problem and try them all at once, increasing efficiency on an astronomical scale.

As told by American cryptographer Bruce Schneier, Chinese researchers appear to have combined “classical lattice reduction factorization techniques with an approximate quantum optimization algorithm” that successfully factored 48-bit numbers using a 10-qubit quantum computer. “And while there are always potential problems when you scale something like this up by a factor of 50, there are no obvious barriers,” Schneier commented.

Security expert Roger Grimes also added:

“Apparently what happened is another guy had previously announced that he was able to break traditional asymmetric encryption using classical computers … but reviewers found a flaw in his algorithm and that guy had to retract his paper. But this Chinese team realized that the step that killed it all could be solved with tiny quantum computers. So they tested and it worked.”

Schneier also warned that the algorithm relies on a recent factoring paper written by Peter Schnorr, where the algorithm works well with small chunks but falls apart at larger sizes, with no tangible explanation. “So if it is true that the Chinese paper relies on this Schnorr technique that does not scale, the techniques in this Chinese paper will not scale either,” Schneier wrote.

“Generally, the smart bet is that the new techniques won’t work. But one day that bet will be wrong.”

Quantum computers are also limited by operational factors such as heat loss and the requirement for a complex -273°C (-459.4°F) cooling infrastructure. Thus, the number of nominal qubits required to invert cryptographic algorithms is likely far higher than theoretical estimates.

Although researchers have not yet done so, the methodology may be theoretically replicable to other RSA-2048 protocols used in information technology, such as HTTPS, e-mail, web surfing, two-factor authentication, etc. Ethereum (ETH) co-founder Vitalik Buterin previously stated his long-term goals to include making the blockchain quantum resistant. Theoretically, this involves branching the network to use a higher-order encryption algorithm that would require larger qubits to break.

Cointelegraph editor Jeffrey Albus contributed to this story.