A method for execution by a dispersed storage and task (DST) processing unit includes transforming a counter seed into a set of counter values; obtaining an encryption key; encrypting at least two portions of data utilizing the encryption key and at least two of the set of counter values, in parallel, to produce at least two ciphertexts; performing a first deterministic function on the at least two ciphertexts, in parallel, to produce at least two transformed ciphertexts; performing a second deterministic function on the at least two transformed ciphertexts to produce a mask; masking the encryption key using the mask to produce a masked key; and combining the at least two ciphertexts and the masked key to produce secure data.