how to do bitwise exclusive or of two strings in python

Question

I would like to perform a bitwise exclusive or of two strings in python  but xor of strings are not allowed in python  How can I do it

User · Answer

For bytearrays you can directly use XOR    gt  gt  gt  b1   bytearray  test123    gt  gt  gt  b2   bytearray  321test    gt  gt  gt  b   bytearray len b1    gt  gt  gt  for i in range len b1          b i    b1 i    b2 i    gt  gt  gt  b bytearray b GWB x00TAG

User · Answer

If you want to operate on bytes or words then you ll be better to use Python s array type instead of a string  If you are working with fixed length blocks then you may be able to use H or L format to operate on words rather than bytes  but I just used  B  for this example    gt  gt  gt  import array  gt  gt  gt  a1   array array  B    Hello  World     gt  gt  gt  a1 array  B    72  101  108  108  111  44  32  87  111  114  108  100  33    gt  gt  gt  a2   array array  B     secret  3    gt  gt  gt  for i in range len a1        a1 i     a2 i     gt  gt  gt  a1 tostring      x00 x0f x1e nXS2 x0c x00 t x10R

User · Answer

def xor strings s1  s2       max len   max len s1   len s2       s1    chr 0     max len - len s1       s2    chr 0     max len - len s2       return    join  chr ord c1    ord c2   for c1  c2 in zip s1  s2

User · Answer

You can convert the characters to integers and xor those instead   l    ord a    ord b  for a b in zip s1 s2     Here s an updated function in case you need a string as a result of the XOR   def sxor s1 s2             convert strings to a list of character pair tuples       go through each tuple  converting them to ASCII code  ord        perform exclusive or on the ASCII code       then convert the result back to ASCII  chr        merge the resulting array of characters as a string     return    join chr ord a    ord b   for a b in zip s1 s2     See it working online  ideone

User · Answer

Below illustrates XORing string s with m  and then again to reverse the process    gt  gt  gt  s  hello  world   gt  gt  gt  m  markmarkmark   gt  gt  gt  s    join chr ord a  ord b   for a b in zip s m    gt  gt  gt  s   x05 x04 x1e x07 x02MR x1c x02 x13 x1e x0f   gt  gt  gt  s    join chr ord a  ord b   for a b in zip s m    gt  gt  gt  s  hello  world   gt  gt  gt

User · Answer

Do you mean something like this   s1    00000001  s2    11111110  int s1 2    int s2 2

User · Answer

Based on William McBrine s answer  here is a solution for fixed-length strings which is 9  faster for my use case   import itertools import struct def make strxor size       def strxor a  b  izip itertools izip  pack struct pack  unpack struct unpack  fmt   dB    size           return pack fmt    a   b for a  b in izip unpack fmt  a   unpack fmt  b         return strxor strxor 3   make strxor 3  print repr strxor 3  foo    bar

User · Answer

the one liner for python3 is     def bytes xor a  b        return bytes x   y for x  y in zip a  b     where a  b and the returned value are bytes   instead of str   of course  can t be easier  I love python3

User · Answer

If the strings are not even of equal length  you can use this  def strxor a  b         xor two strings of different lengths     if len a   gt  len b           return    join  chr ord x    ord y   for  x  y  in zip a  len b    b        else          return    join  chr ord x    ord y   for  x  y  in zip a  b  len a

User · Answer

def strxor  s0  s1     l     chr   ord  a    ord  b    for a b in zip  s0  s1      return    join  l     Based on Mark Byers answer

User · Answer

Here is your string XOR er  presumably for some mild form of encryption    gt  gt  gt  src    Hello  World    gt  gt  gt  code    secret   gt  gt  gt  xorWord   lambda ss cc     join chr ord s  ord c   for s c in zip ss cc 100    gt  gt  gt  encrypt   xorWord src  code   gt  gt  gt  encrypt    x00 x0f x1e nXS2 x0c x00 t x10R   gt  gt  gt  decrypt   xorWord encrypt code   gt  gt  gt  print decrypt Hello  World    Note that this is an extremely weak form of encryption   Watch what happens when given a blank string to encode    gt  gt  gt  codebreak   xorWord           code   gt  gt  gt  print codebreak SECRET

User · Answer

I ve found that the    join chr ord a  ord b   for a b in zip s m   method is pretty slow  Instead  I ve been doing this   fmt     dB    len source  s   struct unpack fmt  source  m   struct unpack fmt  xor data  final   struct pack fmt    a   b for a  b in izip s  m

[python] how to do bitwise exclusive or of two strings in python?

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