Well I have an assignment to implement DES and I chose python, only problem is I can't figure out how to XOR bits of a String or Byte String, I can manually XOR them if only I can manage to read the 1s and 0s in them.
Example:
s1 = b'abc'
s2 = b'efg'
s3 = XOR(s1,s2) // my own method
How can I XOR them or how can I get the binary values of 1s and 0s that represent them?
If you use any python methods explain them, I'm relatively new to this language.
First you need to zip your strings then use ord (in python 2) and ^ for each of characters :
>>> s1 = b'abc'
>>> s2 = b'efg'
>>> ''.join(chr(ord(i)^ord(j)) for i,j in zip(s1,s2))
'\x04\x04\x04'
the ord() function retuen value of the byte when the argument is an 8-bit string.But if you are using python 3 you dont need ord :
>>> ''.join(chr(i^j) for i,j in zip(s1,s2))
'\x04\x04\x04'
Since bytes objects are sequences of integers (akin to a tuple), for a bytes object b,
b[0]will be an integer, whileb[0:1]will be a bytes object of length 1. (This contrasts with text strings, where both indexing and slicing will produce a string of length 1)
example :
>>> s1[0]
97
>>> s1[0:1]
b'a'
and if you want to convert back your strings you need to firs convert the XORed string to binary you can do it by binascii.a2b_qp function :
>>> import binascii
>>> s=''.join(chr(i^j) for i,j in zip(s1,s2))
>>> s4=binascii.a2b_qp(s)
>>> ''.join(chr(i^j) for i,j in zip(s1,s4))
'efg'