hash function "hash function" an algorithm mapping or translating one sequence of bits into another generally smaller set, known as the hash result, such that - (a) a message yields the same hash result every time the algorithm is executed using the same message as input; (b) it is computationally infeasible that a message can be derived or reconstituted from the hash result produced by the algorithm; and (c) it is computationally infeasible that two messages can be found that produce the same hash result using the algorithm; PU(A) 359/1998 - DIGITAL SIGNATURE REGULATIONS 1998 2. Interpretation.