base64 decode and byte negotiate string

Question

I have base64 encoded string sZCLmg== which is Note. What I am trying to do is to decode it with base64 and then use bytes negotiation to get string Note back.

import base64 encoded = 'sZCLmg==' #sZCLmg== Note data = base64.b64decode(encoded) print data mylist = [] mylist.append(data) #print mylist[0][0] bytes = mylist[0][0] print (bytes ^ 0xFF)

but I am getting error: ValueError: invalid literal for int() with base 10: '\xb1' Any idea please what am I doing wrong to get original string Note?

Are you sure that's the correct encoded string? I'm getting Tm90ZQ== for Note — shriakhilc
– shriakhilc, Commented May 26, 2019 at 16:13
@TheGamer007, apparently the bytes were negated before Base64 encoding. — wovano
– wovano, Commented May 31, 2019 at 0:01

snakecharmerb · Accepted Answer · 2019-05-31 05:51:45Z

In Python2, iterating over the literal '\xb1\x90\x8b\x9a' produces strings, not bytes.

One solution would be to use a bytearray.

>>> ba = bytearray(data) >>> ''.join(chr(x ^ 0xFF) for x in ba) 'Note'

As @wovano points out in the comments, also it's possible to do this without using a bytearray, like this:

''.join(chr(ord(x) ^ 0xFF) for x in data)

Yes, it results in strings, which cannot be xor'ed with 0xFF. But using bytearray is not necessary. The following gives the same result: ''.join(chr(ord(x) ^ 0xFF) for x in data).

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