1. A machine-readable non-transitory storage medium having instructions therein, which when executed by a machine, cause the machine to perform a method, the method comprising: providing a non-linear permutation operation on a sequence of bits in a data unit, wherein more than one representable values are associated with the data unit, each representable value corresponding to a possible binary value of the sequence of bits, a message data represented via a plurality of representable values of the data unit; performing a sequence of permutation operations to generate a representation of a bijection mapping relationship on the representable values of the data unit, wherein the sequence of permutation operations include one or more of the non-linear permutation operation, wherein the sequence of permutation operations depends on the message data, the bijection mapping relationship corresponding to a particular permutation operation on the sequence of bits; generating a plurality of permuted values respectively from a plurality of index values via the particular permutation operation, each permuted value corresponding to one of the index values permuted via the particular permutation operation, each index value belonging to the representable values of the data unit, the index values independent of the message data; and performing combination operations on the permuted values for a hash data representing a cryptographic hash of the message data.