Modular Exponentiation used in the RSA public key cryptographic system

mod_exp.py

"""
Modular Exponentiation (Rapid Exponentiation)
---------------------------------------------
Efficient algorithm used in the RSA public key cryptographic system

More info:
  https://en.wikipedia.org/wiki/Modular_exponentiation
"""
from time import time

def modexp(b,e,m):
	r=1
	while(e):
		if(e&1): r=(r*b)%m
		b,e=(b**2)%m,e>>1
	return r

def main():
    print("calculate: (b**e) mod m")
    b=int(input("b (base): "))
    e=int(input("e (exponent): "))
    m=int(input("m (module): "))
    print("-"*5,"[result]","-"*5)
    ti=time()
    print(modexp(b,e,m))
    tf=time()
    print(f"calculation time: {tf-ti}")
    
if __name__ == "__main__":
    main()