AN ELECTRONIC CALCULATING DEVICE ARRANGED TO CALCULATE THE PRODUCT OF INTEGERS

An electronic calculating device (100; 200) arranged to calculate the product of integers, the device comprising a storage (110) configured to store integers (210, 220) in a multi-layer residue number system (RNS) representation, the multi-layer RNS representation having at least an upper layer RNS and a lower layer RNS, the upper layer RNS being a residue number system for a sequence of multiple upper moduli (Mi), the lower layer RNS being a residue number system for a sequence of multiple lower moduli (mi), an integer (x) being represented in the storage by a sequence of multiple upper residues (xi=(x)Mi; 211, 221) modulo the sequence of upper moduli (Mi), upper residues (xj; 210.2, 220.2) for at least one particular upper modulus (Mj) being further-represented in the storage by a sequence of multiple lower residues ((xj)mj, 212, 222) of the upper residue (xj) modulo the sequence of lower moduli (mi), wherein at least one of the multiple lower moduli (mi) does not divide a modulus of the multiple upper moduli (Mj).