Examples relate to efficient storage of initialization vectors in a system. One example facilitates determining an initialization vector for use in encrypting a first cache line of a first page of memory, wherein determining the initialization vector comprises concatenating a page-level counter with a first set of hierarchical counters. The first set of hierarchical counters includes a first counter associated with the first cache line; a first group counter associated with a first group of cache lines, the first group of cache lines comprising the first cache line; and a first cluster counter associated with a first cluster of cache line groups, the first cluster comprising the first group of cache lines.