C/C++ :: Vigenere Cipher Not Decoding

I was assigned to make a vigenere cipher using the function void vegenere(char* to_encrypt, char* key, char* encrypted) I got it to work for the encryption but i have to be able to decrypt the phrase too. I was assigned to write in a flag which indicated encryption or decryption. I tried to implement this but now it wont decrypt and i dont know why, all it does is put the same copy of decryption (which is really encrypted) multiple times until it crashes.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
void decrypt(char *to_encrypt, char *key);
enum flag{encryption = 1, decryption = -1};

[Code] ....

Ok i found my dumb error of putting decrypt on an infinite loop which i fixed by putting it into the if statement after the encryption output. However now it says that the encrypted and decrypted outputs are identical without decrypting the ciphertext