A cryptographic accelerator (processor) retrieves data blocks for processing from a memory. These data blocks arrive and are stored in an input buffer in the order they were stored in memory (or other known order)—typically sequentially according to memory address (i.e., in-order.) The processor waits until a certain number of data blocks are available in the input buffer and then randomly selects blocks from the input buffer for processing. This randomizes the processing order of the data blocks. The processing order of data blocks may be randomized within sets of data blocks associated with a single read transaction, or across sets of data blocks associated with multiple read transactions.