This part of ISO/IEC 10118 specifies two hash-functions which make use of modular arithmetic. These hash-functions, which are believed to be collision-resistant, compress messages of arbitrary but limited length to a hash-code whose length is determined by the length of the prime number used in the reduction-function defined in 7.3. Thus, the hash-code is easily scaled to the input length of any mechanism (e.g., signature algorithm, identification scheme).

The hash-functions specified in this part of ISO/IEC 10118, known as MASH-1 and MASH-2 (Modular Arithmetic Secure Hash) are particularly suitable for environments in which implementations of modular arithmetic of sufficient length are already available. The two hash-functions differ only in the exponent used in the round-function.