A configurable sponge function engine. The configurable engine includes a state register having bitrate and capacity sections, each having a variable size, where a sum of the bitrate and capacity sizes is fixed. A controller generates a bitrate size indication. A configurable message processor receives an input message from an input bus, receives the size indication, fragments the input message into fragmented blocks of a size specified by the size indication, and converts the blocks to a bus width of the bitrate and capacity sizes. An iterative calculator receives the blocks, performs iterative processing operations on the blocks, and stores a result of each operation in the state register overwriting a previous register value. An output adaptor receives a value stored in the state register after the block corresponding to the end of the input message is processed and outputs the register value converted to have an output bus width.