Isomorphic number theoretic transforms

It is noted that the computational cost of circular convolutions can be reduced to a large extent by using number-theoretic transforms (NTTs). The author proposes a novel algorithm for removing the necessity for the transforming element of the NTT to be coincident with a power of 2. The algorithm is based on the isomorphic correspondence between the multiplication mod M and the addition mod (M-1), where M is a prime modulus. The NTT is performed completely in the isomorphic domain, attaining in this way a reduced computation cost without sacrificing the length of the NTT