Apparatus and method for enacting data security in a data storage device, such as by protecting against a differential power analysis (DPA) attack. In some embodiments, a dithered clock signal is generated having a succession of clock pulse segments. Each of the clock pulse segments has a different respective frequency selected in response to a first random number and a different overall duration selected in response to a second random number. The different segment frequencies are selected by supplying the first random number to a lookup table, and the different segment durations are obtained by initializing a timer circuit using the second random number. The dithered clock signal is used to clock a programmable processor during execution of a cryptographic function.