Post Quantum Cryptography

This week sees a meeting at the Newton Institute in Cambridge on what would happen to cryptography as soon as a quantum computer is built. For those who know nothing about quantum computers, the problem is that a quantum computer would break all our existing public key algorithms. It would also affect symmetric primitives such as block ciphers and hash functions; but for these it is easier to mitigate the threat.

The meeting consisted of a series of talks to motivate research in this area. After scene setting in the first morning, the main talks started in the afternoon. Ashley Montanaro from Bristol gave a nice overview of existing quantum algorithms. Including a method to attack deterministic fully homomorphic encryption using a quantum computer. Nigel Smart from Bristol then gave a talk on the current best-in-class quantum secure public key technology which are based on lattices. Kenny Paterson from Royal Holloway then talked about the problems in legacy applications using deprecated cryptography such as MD5. Tomorrow, the second day, will see talks by Joop van de Pol (Bristol) and others on further applications of lattices to cryptography.

The main issue discussed was about the threat of quantum computing. If it will happen in the next few years (or decades), then we need now to change our cryptographic infrastructure to cope with this. However, even if something does not happen we still need to worry about replacing our current cryptography at scale. Especially for current systems which need to be forward secure.