1. A method for execution by a computing device, the method comprises: receiving a store data object message; determining at least a portion of the data object; determining an encryption key based on the at least a portion; determining a key reference of the encryption key; retrieving a prior encryption key with a similar key reference from dispersed storage network (DSN) memory; calculating a difference key based on the encryption key and the prior encryption key; and creating encryption key information including the difference key and the similar key reference of the prior encryption key.