Quantum-resistant algorithms sounds like a hacky plot device on an episode of Star Trek: Voyager. But in this article, security researcher Bruce Schneier breaks down why the advent of quantum computing requires us to rethink how we approach cryptography, especially public-key based approaches. Traditionally, symmetrical crytography relies on the fact that it’s a lot easier to multiply two prime numbers together than it is to factor them back to the originals. This imbalance, which is largely maintained with classical computing, can break down once qubits enter the equation.
As the article points out, this isn’t a looming threat, given that quantum computers are in their infancy. But security researchers are thinking about how to harden encryption against the potential new reality. What’s really interesting is entertaining the idea that traditional symmetrical encryption eventually becomes irredeemable in the age of quantum computing, and considering what other means of privacy and security are out there. As Bruce says: It’s a weird future.
Bruce Schneier comments:
Quantum computers promise to upend a lot of this. Because of the way they work, they excel at the sorts of computations necessary to reverse these one-way functions. For symmetric cryptography, this isn’t too bad. Grover’s algorithm shows that a quantum computer speeds up these attacks to effectively halve the key length. This would mean that a 256-bit key is as strong against a quantum computer as a 128-bit key is against a conventional computer; both are secure for the foreseeable future.
Read more at: Quantum Computing and Cryptography