Exhaustive search for encryption keys
To convert an integer to a bit string with a particular number of digits, use string.format with the b format type. For example:

&gt;&gt;&gt; ['{0:04b}'.format(i) for i in range(16)]
['0000', '0001', '0010', '0011', '0100', '0101', '0110', '0111',
 '1000', '1001', '1010', '1011', '1100', '1101', '1110', '1111']


But really it looks to me as though you don't want to be working with bit strings at all. You just want to be working with integers.

So instead of get_all, just write range(16) and instead of bytexor, write ^. Your entire program can be written like this:

from itertools import product
for a, b, c, d, e in product(range(16), repeat=5):
    if a ^ c ^ d == 3 and a ^ c ^ e == 10 and a ^ b ^ c ^ d == 6:
        print a, b, c, d, e, a ^ b ^ c ^ e


(This will also run a lot faster without all that fiddling about with strings.)