A method begins by a dispersed storage (DS) processing module segmenting a data partition into a plurality of data segments. For a data segment of the plurality of data segments, the method continues with the DS processing module dividing the data segment into a set of data sub-segments and generating a set of sub keys for the set of data sub-segments based on a master key. The method continues with the DS processing module encrypting the set of data sub-segments using the set of sub keys to produce a set of encrypted data sub-segments and aggregating the set of encrypted data sub-segments into encrypted data. The method continues with the DS processing module generating a masked key based on the encrypted data and the master key and combining the encrypted data and the masked key to produce an encrypted data segment.