Despite many proposals, few hash functions based on modular arithmetic have withstood attack, and most that have tend to be relatively inefficient. MASH-1 evolved from a long line of related proposals successively broken and repaired.
Committee Draft ISO/IEC 10118-4 (Nov 95)
MASH-1 involves use of an RSA-like modulus M, whose bitlength affects the security. M should be difficult to factor, and for M of unknown factorization, the security is based in part on the difficulty of extracting modular roots. M also determines the block size for processing messages.
There is a new version of the algorithm called MASH-2 with a different exponent. The original <math>e=2</math> is replaced by <math>e=2^8+1</math>.