Electronic device and method for performing number theoretic transforms (NTTs) on polynomials for cryptography uses an arithmetic transformation on an input polynomial with n coefficients to divide the input polynomial into multiple polynomials each with less than n coefficients such that the coefficients of the multiple polynomials add up to n. An NTT transformation is executed on the multiple polynomials such that the coefficients of each of the multiple polynomials are processed in parallel butterfly operations. A cryptographic operation is performed based on the results of the NTT transformation.