Abstract: A system and circuit for generating a variable sized hash output using a single hash and mixing function are disclosed. In one embodiment, a system for generating a variable sized hash output data includes a hash function module for generating an N bit hash result data by processing an M bit input data. The system also includes a mixing function module including a plurality of logic gates which implement a set of reversible arithmetic functions for generating an N bit hash output data by processing the N bit hash result data using the set of reversible arithmetic functions, where a subset of the N bit hash output data is used as the variable sized hash output data, and a size of the subset of the N bit hash output data is less than N bits.