Interactive proofs can be used to prove you have a secret without divulging it (http://en.wikipedia.org/wiki/Zero_knowledge_proofs) hence their mentioning of crypto.
These systems can be attacked in various ways, one of which is to use quantum entanglement. Edited to add: since the interactive proofs rely on probabilistically estimating the likelihood respondents can still be lying, quantum effects can be used to reduce the accuracy of these estimates. In this case, entanglement is used as a means of collusion between supposedly independent respondents.
What these researchers did was take an interactive proof that was already created to be resilient against these quantum attacks , and have demonstrated that it is in fact resilient against them.