A method begins by a dispersed storage (DS) processing module encrypting a data segment utilizing an encryption key to produce an encrypted data segment and performing a deterministic function on the encrypted data to produce a transformed representation of the encrypted data. The method continues with the DS processing module masking the encryption key utilizing the transformed representation of the encrypted data to produce a masked key, partitioning the masked key into a plurality masked key partitions, partitioning the encrypted data segment into a plurality of encrypted data segment partitions, and combining the plurality of masked key partitions with the plurality of encrypted data segment partitions to produce a plurality of combined partitions. For a combined partition of the plurality of combined partitions, the method continues with the DS processing module encoding the combined partition using a dispersed storage error coding function to produce a set of encoded data slices.