Abstract: A modular polynomial multiplier includes a plurality of processing elements. Each includes a multiplication unit, an addition unit and a delay unit. The addition unit has an input connected to the output of the multiplication unit. The delay unit is connected to the output of the addition unit delays values by one clock cycle. The first input of the multiplication unit of each processing element carries a respective coefficient of a first polynomial and the second input of the multiplication unit of each processing element is connected to one of an input line carrying a sequence of coefficients of a second polynomial having n coefficients and a delay line carrying the sequence of coefficients of the second polynomial delayed by n clock cycles and negated.