1. A method comprises: receiving, from a requesting device, a data storage request that includes data for storage; determining whether substantially identical data is currently stored in a dispersed storage network (DSN) memory; and when the substantially identical data is not stored in the DSN memory: encoding at least a portion of the data using an error coding dispersal storage function to produce a set of encoded data slices; sending the set of encoded data slices to the DSN memory for storage therein; and generating a unique retrieval matrix for the requesting device, wherein the unique retrieval matrix identifies a sub-set of encoded data slices of the set of encoded data slices for subsequent retrieval of the at least a portion of the data.