How to XOR two strings in Python

Question

H, I'm trying to XOR two strings (which should become hex first) in Python. I know one way will work:

def xor_two_str(str1, str2):
    return hex(int(str1,16) ^ int(str2,16))

But I tried sth like this:

def change_to_be_hex(str):
    return hex(int(str,base=16))
def xor_two_str(str1,str2):
    a = change_to_be_hex(str1)
    b = change_to_be_hex(str2)
    return hex(a ^ b)
print xor_two_str("12ef","abcd")

This will return TypeError: ^ shouldn't be used between str, str. I don't know why.

And also this function won't work:

bcd = change_to_be_hex("12ef")
def increment_hex(hex_n):
   return hex_n + 1
result = increment_hex(bcd)
print result

The error message is : TypeError: cannot concatenate 'str' and 'int' objects I feel this is so strange:(

Thank you!

Answer 1

Hi, The following function is returning the result of hex() which returns a string.

def change_to_be_hex(s):
    return hex(int(s,base=16))

You should use the ^ operator on integers.

def change_to_be_hex(s):
    return int(s,base=16)
    
def xor_two_str(str1,str2):
    a = change_to_be_hex(str1)
    b = change_to_be_hex(str2)
    return hex(a ^ b)
print(xor_two_str("12ef","abcd"))

I'm not sure though that's the result you're looking for. If you want to XOR two strings, it means you want to XOR each character of one string with the character of the other string. You should then XOR ord() value of each char or str1 with ord() value of each char of str2.

def xor_two_str(a,b):
    xored = []
    for i in range(max(len(a), len(b))):
        xored_value = ord(a[i%len(a)]) ^ ord(b[i%len(b)])
        xored.append(hex(xored_value)[2:])
    return ''.join(xored)
    
print(xor_two_str("12ef","abcd"))

Or in one line :

def xor_two_str(a,b):
    return ''.join([hex(ord(a[i%len(a)]) ^ ord(b[i%(len(b))]))[2:] for i in range(max(len(a), len(b)))])

print(xor_two_str("12ef","abcd"))

Answer 2

hex returns a string, so you're trying to xor two strings.

def change_to_be_hex(s):
   return int(s,base=16)

Should fix this.

Answer 3

when you initially return hex, like in change_to_be_hex, you explicitly convert it to int. you need to do that throughout your code to add something to it - so, change increment_hex to:

return (int(hex_n) + 1)