XOR

XOR is a bit-wise binary operation that is commonly written as ^ in programming languages.

Each character in a string is essentially represented as bytes, to which XOR is applied.

XOR Cipher

XOR Cipher elaborates on the idea of applying XOR to each to byte, one in the data and one in the key.

Here are our XOR Cipher empty functions:

def cyclic_xor(data: bytes, key: bytes) -> bytes:
    ...


def cyclic_xor_string(string: str, key: str, encoding: str = ..., errors: str = ...) -> str:
    ...

XOR Cipher pairs each byte in the string with a byte in the key (which is cycled), then applies XOR operation for each pair.

Returning back to our functions:

from itertools import cycle

DEFAULT_ENCODING = "utf-8"
DEFAULT_ERRORS = "strict"


def cyclic_xor(data: bytes, key: bytes) -> bytes:
    return bytes(byte ^ key_byte for byte, key_byte in zip(data, cycle(key)))


def cyclic_xor_string(
    string: str, key: str, encoding: str = DEFAULT_ENCODING, errors: str = DEFAULT_ERRORS
) -> str:
    result = cyclic_xor(string.encode(encoding, errors), key.encode(encoding, errors))

    return result.decode(encoding, errors)

XOR Cipher can also use one byte as the key:

def xor(data: bytes, key: int) -> bytes:
    return bytes(byte ^ key for byte in data)


def xor_string(
    string: str, key: str, encoding: str = DEFAULT_ENCODING, errors: str = DEFAULT_ERRORS
) -> str:
    result = xor(string.encode(encoding, errors), key.encode(encoding, errors))

    return result.decode(encoding, errors)

XOR Keys

Here is a list of XOR keys currently used in GD:

Key	Usage
14251	Messages
26364	Level Password
37526	User Password
39673	Level Leaderboard
41274	Level Seed
29481	Comment Check
19847	Challenges
59182	Rewards
58281	Like and Rate
85271	User Profile
19283	Vault Codes
48291	Load Data