This thesis is focused on hash families and cover-free families and their application to
problems in cryptography. We present new necessary conditions for generalized separating
hash families, and provide new explicit constructions. We then consider three cryptographic
applications of hash families and cover-free families. We provide a stronger de nition of
anonymity in the context of shared symmetric key primitives and give a new scheme with
improved anonymity properties. Second, we observe that nding the invalid signatures
in a set of digital signatures that fails batch veri cation is a group testing problem, then
apply and compare many group testing algorithms to solve this problem e ciently. In
particular, we apply group testing algorithms based on cover-free families. Finally, we
construct a one-time signature scheme based on cover-free families with short signatures
