XOR Cipher

XOR Encryption is an encryption method used to encrypt data and is hard to crack by brute-force method, i.e generating random encryption keys to match with the correct one.

Below is a simple implementation in C++. The concept of implementation is to first define a XOR – encryption key and then to perform XOR operation of the characters in the String with this key which you want to encrypt. To decrypt the encrypted characters we have to perform XOR operation again with the defined key. Here we are encrypting the entire String.





// C++ program to implement XOR - Encryption
// The same function is used to encrypt and
// decrypt
void encryptDecrypt(char inpString[])
    // Define XOR key
    // Any character value will work
    char xorKey = 'P';
    // calculate length of input string
    int len = strlen(inpString);
    // perform XOR operation of key
    // with every caracter in string
    for (int i = 0; i < len; i++)
        inpString[i] = inpString[i] ^ xorKey;
// Driver program to test above function
int main()
    char sampleString[] = "GeeksforGeeks";
    // Encrypt the string
    printf("Encrypted String: ");
    // Decrypt the string
    printf("Decrypted String: ");
    return 0;



Encrypted String: 55;#6?"55;#
Decrypted String: GeeksforGeeks

The basic idea behind XOR – encryption is, if you don’t know the XOR-encryption key before decrypting the encrypted data, it is impossible to decrypt the data. For example, if you XOR two unknown variables you cannot tell that what the output of those variables are. Consider the operation A XOR B, and this returns true. Now if the value of one of the variable is known we can tell the value of other variable. If A is True then B should be False or if A is False then B should be true according to the properties of the boolean XOR operation. Without knowing one of the value we can not decrypt the data and this idea is used in XOR – encryption.

Related Articles:
Vigenère Cipher
Caesar Cipher

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