#!/bin/env python3
# This is simple implementation of RSA algorithm
import random
# Global Variables
num=0;
primes = []
a=0
b=0
m=0
n=0
e=0
d=0
c=0
p=0
msg=0
# Check if n is prime number or not
def is_prime(n):
for i in range(2,int(n**0.5)+1):
if n%i==0:
return False
return True
# Generates prime number upto range
def gen_primes(rang):
for possiblePrime in range(2, rang):
# Assume number is prime until shown it is not.
isPrime = True
for num in range(2, possiblePrime):
if possiblePrime % num == 0:
isPrime = False
if isPrime:
primes.append(possiblePrime)
# print(primes)
# Greatest common divisor(HCF)
def gcd(a,b):
if(b==0):
return a
else:
return gcd(b,a%b)
# Main rsa algorithm
def rsa():
global a
global b
global m
global n
global e
global d
global c
global p
# p=int(s)
p=int(msg)
a=0
b=0
# Generate prime number upto given range and save to 'primes' arrary
gen_primes(2000)
# Generate Two Large Prime Numbers, a and b from arrary
# a and b shouldn't be equal
while(a==b):
a=(random.choice(primes))
b=(random.choice(primes))
print("value of a is", a);
print("value of b is", b,"\n");
# Calculate m and n
n=a*b
m=(a-1)*(b-1)
print("value of m is", m);
print("value of n is", n,"\n");
# N should be greater than p, else value of p is not accurate
if n<p:
# Start again if n<p
print("<--- Value of n < p. Starting again --->\n")
return rsa()
# Choose a small number e (1 < e < m), coprime to m such that GCD(e, m) = 1.
for i in range(2,m):
gcdVal=gcd(i,m)
print("gcd of",i,"and",m,"==>",gcdVal)
if gcdVal==1:
e=i
break
print("value of e is", e);
# Find d, such that de % m = 1. Where d = (1 + m * i)/e
# search until d is integer value
for i in range(1,m):
print("\nAt i =", i);
d = (1 + m * i) / e
print("value of d is", d);
b = d / int(d)
if b==1.0:
break
d=int(d)
print("Required value of d is",d)
# Calling for public_key function with encryption value 'e' and value of n to encrypt user message
public_key(n,e)
return
# Encryption Algorithm used by anyone with public key
# C = P^e % n
def public_key(x,y):
print("\nEncryption");
global c
global p
global n
global e
n = x
e = y
print("value of e is", e);
print("value of n is", n);
c = (p**e) % n
print("value of c is", c);
# Call decryption function with decryption value(d), 'n' and 'c'
private_key(n,d,c)
# Decryption Algorithm used by owner of private key
# P = C^e % n
def private_key(x,y,z):
print("\nDecryption");
global p
global n
global e
c=z
n = x
d = y
print("value of c is", c);
print("value of d is", d);
print("value of n is", n);
p = (c**d) % n
print("Your input value was",msg,"and decrepted value is", p);
# Main function
def main():
global msg
msg = input("Enter your message (Represented by any integer value): ")
rsa()
# print(gen_prime.generate_prime_number())
if __name__ == '__main__':
main()
