rsa-small-numbers.cpp

00001 #include<iostream>
00002 #include<math.h>
00003 
00004 int gcd(int a, int h)
00005 {
00006     int temp;
00007     while (1)
00008     {
00009         temp = a%h;
00010         if (temp == 0)
00011           return h;
00012         a = h;
00013         h = temp;
00014     }
00015 }
00016 
00017 int main()
00018 {
00019     double p = 3;
00020     double q = 7;
00021     double n = p*q;
00022     double e = 2;
00023     double phi = (p-1)*(q-1);
00024     while (e < phi)
00025     {
00026        
00027         if (gcd(e, phi)==1)
00028             break;
00029         else
00030             e++;
00031     }
00032 
00033     int k = 2; 
00034     double d = (1 + (k*phi))/e;
00035 
00036     double msg = 20;
00037 
00038     printf("Message data = %lf", msg);
00039     double c = pow(msg, e);
00040     c = fmod(c, n);
00041     printf("\nEncrypted data = %lf", c);
00042 
00043     double m = pow(c, d);
00044     m = fmod(m, n);
00045     printf("\nOriginal Message Sent = %lf", m);
00046 
00047     return 0;
00048 }