Quantum Technology and Its Impact on Cryptography

Public key (PK) cryptography is used ubiquitously for digital signatures and for key establishment. The security of public key cryptography depends on it being infeasible to compute the private key associated with some public key. The evolution of quantum computers undermines the security of PKI: Shor’s quantum factoring algorithm is an efficient quantum algorithm for recovering private keys from public keys. Shor’s algorithm remains efficient for all practical key sizes: the threat cannot be mitigated by using larger keys. I will describe how investment and progress in realising a quantum computer is rapidly accelerating world-wide. We therefore need to end reliance upon cryptographic primitives that are vulnerable to Shor’s algorithm. New approaches that are “quantum safe” need to be developed with some urgency. Quantum systems provide one approach, QKD (Quantum Key Distribution) where security of information is ensured by the laws of physics, regardless of technological advances. Current research is focused on practical implementations, ensuring that implementation does not introduce vulnerabilities and developing long distance and especially satellite communications. A second tool, Post-Quantum Public Key Cryptography (or Quantum Safe encryption) is being actively investigated. Various different kinds of mathematical structure have been suggested for building post-quantum public key primitives. Each kind of structure requires acceptance of some computational-hardness assumptions associated with that structure. I will advocate that a transition from current Public Key Cryptography to a combination of Post-Quantum Cryptography and QKD will be the most appropriate way forward for the majority of users of cryptographic solutions in dealing with the very imminent quantum threat? Recorded October 2020 from TelecomTV Studio A