This illustration of a block cipher appears in several horizontal layers. The first layer is depicted as a single long rectangle labeled "64-bit input." Below this is as series of small rectangles, eight in total, arranged horizontally and each labeled "8 bits." Blue arrows extend from the first layer to each of the rectangles labeled "8 bits." Blue arrows extend from each of the 8 bit rectangles to a circle below it. Each circle appears directly below the 8 bit rectangle, and each is labeled "T1" through "T8." Blue arrows extend from each of these circles to another layer of small rectangles labeled "8 bits." And arrows extend from these rectangles to another single long rectangle, this one labeled "64-bit scrambler." Blue arrows extend in a crisscross pattern to another single long rectangle, this one labeled "64-bit output." A blue arrow extends from the 64-bit output rectangle to the left and up and points back to the original single long rectangle labeled "64-bit input." This arrow is labeled "Loop for n rounds."