Residue number systems provide a good means for extremely long integer
arithmetic. Their carry-free operations make parallel implementations
feasible. Some applications involving very long integers, such as pub
lic key encryption, rely heavily on fast module reductions. This paper
shows a new combination of residue number systems with efficient modu
le reduction methods. Two methods are compared, and the faster one is
scrutinized in detail. Both methods have the same order of complexity,
O(log n), with n denoting the amount of registers involved.