DATE: 27 January 2021 SPEAKER: Laura Johnson TITLE: An introduction to External Difference Families and Strong External Difference Families, and their applications to cryptography ABSTRACT: This talk will introduce External Difference Families (EDFs); a type of combinatorial structure consisting of disjoint subsets of a group G, such that each element occurs exactly lambda times as a difference between elements of distinct sets. Strong External Difference Families (SEDFs) will also be introduced; these are EDFs with extra constraints on the exact number of times that each element must occur as a difference between particular sets. We will cover some basic constructions of both structure's and briefly explore their applications to cryptography.