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  1.  
  2. /* This program calculates the Key for two persons  
  3. using the Diffie-Hellman Key exchange algorithm */
  4. #include<stdio.h> 
  5. #include<math.h> 
  6.  
  7. // Power function to return value of a ^ b mod P 
  8. long long int power(long long int a, long long int b, 
  9.                                      long long int P) 
  10. {  
  11.     if (b == 1) 
  12.         return a; 
  13.  
  14.     else
  15.         return (((long long int)pow(a, b)) % P); 
  16. } 
  17.  
  18. //Driver program 
  19. int main() 
  20. { 
  21.     long long int P, G, x, a, y, b, ka, kb;  
  22.  
  23.     // Both the persons will be agreed upon the  
  24.         // public keys G and P  
  25.     P = 23; // A prime number P is taken 
  26.     printf("The value of P : %lld\n", P);  
  27.  
  28.     G = 9; // A primitve root for P, G is taken 
  29.     printf("The value of G : %lld\n\n", G);  
  30.  
  31.     // Alice will choose the private key a  
  32.     a = 4; // a is the chosen private key  
  33.     printf("The private key a for Alice : %lld\n", a); 
  34.     x = power(G, a, P); // gets the generated key 
  35.  
  36.     // Bob will choose the private key b 
  37.     b = 3; // b is the chosen private key 
  38.     printf("The private key b for Bob : %lld\n\n", b); 
  39.     y = power(G, b, P); // gets the generated key 
  40.  
  41.     // Generating the secret key after the exchange 
  42.         // of keys 
  43.     ka = power(y, a, P); // Secret key for Alice 
  44.     kb = power(x, b, P); // Secret key for Bob 
  45.  
  46.     printf("Secret key for the Alice is : %lld\n", ka); 
  47.     printf("Secret Key for the Bob is : %lld\n", kb); 
  48.  
  49.     return 0; 
  50. } 
  51.  
Success #stdin #stdout 0s 9424KB
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stdin
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Standard input is empty
stdout
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The value of P : 23
The value of G : 9

The private key a for Alice : 4
The private key b for Bob : 3

Secret key for the Alice is : 9
Secret Key for the Bob is : 9
https://ideone.com/x6KaFA
language:
C (gcc 8.3)
created:
5 years ago
visibility:
public

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