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  1. #include<iostream>
  2. #include<string>
  3.  
  4. using namespace std;
  5.  
  6. string encrypt(string m, string key){
  7. 	string ciphertext = "";
  8. 	for(int i = 0;i < m.size();i++){
  9. 		ciphertext += ((m[i] - 'A') + (key[i % key.size()] - 'A')) % 26;
  10. 		ciphertext[i] = ciphertext[i] + 'A';
  11. 	}
  12. 	return ciphertext;
  13. }
  14.  
  15. string decrypt(string m, string key){
  16. 	string plaintext = "";
  17. 	for(int i = 0;i < m.size();i++){
  18. 		plaintext += ((m[i] - 'A') - (key[i % key.size()] - 'A')) % 26;
  19. 		if(plaintext[i] < 0) plaintext[i] += 26;
  20. 		plaintext[i] = plaintext[i] + 'A';
  21. 	}
  22. 	return plaintext;
  23. }
  24.  
  25. int main(){
  26. 	string Key = "SET";
  27. 	string message = "TOPSECRET";
  28.  
  29. 	string cipher = encrypt(message, Key);
  30.  
  31. 	cout << cipher << endl;
  32.  
  33. 	string plaintext = decrypt(cipher, Key);
  34.  
  35. 	cout << plaintext << endl;
  36. return 0;
  37. }
  38.  
Success #stdin #stdout 0s 3416KB
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LSIKIVJIM
TOPSECRET
https://ideone.com/M3BAmq
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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