Is A Quantum-Cryptography Apocalypse Imminent?

Will quantum computers crack cryptographic codes and cause a global security disaster? You might certainly get that impression from a lot of news coverage, the latest of which reports new estimates that it might be 20 times easier to crack such codes than previously thought.

Cryptography underpins the security of almost everything in cyberspace, from wifi to banking to digital currencies such as bitcoin. Whereas it was previously estimated that it would take a quantum computer with 20 million qubits (quantum bits) eight hours to crack the popular RSA algorithm (named after its inventors, Rivest–Shamir–Adleman), the new estimate reckons this could be done with 1 million qubits.

By weakening cryptography, quantum computing would present a serious threat to our everyday cybersecurity. So is a quantum-cryptography apocalypse imminent?

Quantum computers exist today but are highly limited in their capabilities. There is no single concept of a quantum computer, with several different design approaches being taken to their development.

There are major technological barriers to be overcome before any of those approaches become useful, but a great deal of money is being spent, so we can expect significant technological improvements in the coming years.

For the most commonly deployed cryptographic tools, quantum computing will have little impact. Symmetric cryptography, which encrypts the bulk of our data today (and does not include the RSA algorithm), can easily be strengthened to protect against quantum computers.

Quantum computing might have more significant impact on public-key cryptography, which is used to set up secure connections online. For example this is used to support online shopping or secure messaging, traditionally using the RSA algorithm, though increasingly an alternative called elliptic curve Diffie-Hellman.

Public key cryptography is also used to create digital signatures such as those used in bitcoin transactions, and uses yet another type of cryptography called the elliptic curve digital signature algorithm.

If a sufficiently powerful and reliable quantum computer ever exists, processes that are currently only theoretical might become capable of breaking those public-key cryptographic tools. RSA algorithms are potentially more vulnerable because of the type of mathematics they use, though the alternatives could be vulnerable too.

Such theoretical processes themselves will inevitably improve over time, as the paper about RSA algorithms is the latest to demonstrate.

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- Author: Keith Martin, The Conversation