A first encoded data slice is received for storage by a DST execution unit from a first vault. A first encryption key corresponding to the first encoded data slice is generated, and a first encrypted data slice is generated by utilizing the first encryption key. A second encoded data slice for second storage by the DST execution unit from a second vault, a second encryption key corresponding the second encoded data slice is generated, and a second encrypted data slice is generated by utilizing the second encryption key. The first encrypted data slice and the second encrypted data slice are stored in a file of a memory of the DST execution unit, where the file and the memory are common to the first encrypted data slice and the second encrypted data slice.