c,algorithm,security,math,encryption , Reverse ^ operator for decryption

Reverse ^ operator for decryption


Tag: c,algorithm,security,math,encryption

I'm trying to reverse the following code in order to provide a function which takes the buffer and decrypts it.

void crypt_buffer(unsigned char *buffer, size_t size, char *key) {
    size_t i;
    int j;

    j = 0;
    for(i = 0; i < size; i++) {
        if(j >= KEY_SIZE)
            j = 0;
        buffer[i] ^= key[j];

I was wordering if a simple buffer[i] ^= (1/key[j]); will be enough to decrypt the encrypted file. But there will be some issues with truncation, isn't it?


This is not a power operator. It is the XOR operator. The thing that you notice for the XOR operator is that x ^ k ^ k == x. That means that your encryption function is already the decryption function when called with the same key and the ciphertext instead of the plaintext.


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I'm trying to reverse the following code in order to provide a function which takes the buffer and decrypts it. void crypt_buffer(unsigned char *buffer, size_t size, char *key) { size_t i; int j; j = 0; for(i = 0; i < size; i++) { if(j >= KEY_SIZE) j = 0;...

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