Fast exponentiation via prime finite field isomorphism

lard and Schnorr algorithm. Farther factorization of prime quadratic integer π = ρρ in the ring 4 [ 2] ±  can be done similarly. Finite field r is represented as quotient ring 4 [ 2] /( ) ± ρ  . Integer exponent k is reduced in corresponding quotient ring by minimization of absolute value of its norm. Algorithms can be used for fast exponentiation in arbitrary cyclic group if its order can be factored in corresponding number rings. If window size is 4 bits, this approach allows speeding-up 2.5 times elliptic curve digital signature verification comparatively to known methods with the same window size.