XOR Starter

Description

XOR is a bitwise operator which returns 0 if the bits are the same, and 1 otherwise. In textbooks the XOR operator is denoted by ⊕, but in most challenges and programming languages you will see the caret ^ used instead. For longer binary numbers we XOR bit by bit: 0110 ^ 1010 = 1100. We can XOR integers by first converting the integer from decimal to binary. We can XOR strings by first converting each character to the integer representing the Unicode character. Given the string label, XOR each character with the integer 13. Convert these integers back to a string and submit the flag as crypto{new_string}. 💡 The Python pwntools library has a convenient xor() function that can XOR together data of different types and lengths. But first, you may want to implement your own function to solve this.

A	B	Output
0	0	0
0	1	1
1	0	1
1	1	0

EXOOR

Since we're lazy, we can use the pwntools library to help us

from pwn import xor

# xor function uses and returns byte strings
label = b"label"
newString = b""

# Iterate over each character
for ch in label:
    # XOR with 13 then append to the string
    newString += xor(ch, 13)

print(newString)

If you're feeling more daring, you can code up your own xor function

def xor(a, b):
    # Note that ASCII characters are represented by bytes
    # For consistency format to binary of 8 bits
    xorString = ""

    # Convert to binary
    # Padded to 8 bits
    binA = '{:08b}'.format(a)
    binB = '{:08b}'.format(b)
    
    # Iterate over each bit and XOR them
    for i in range(len(binA)):
        if binA[i] == binB[i]:
            xorString += "0"
        else:
            xorString += "1"
    
    # Convert binary string to text
    ch = chr(int(xorString, 2))
    b = ch.encode('utf-8') # Return byte
    return b

Flag

crypto{aloha}