Trouble implementing crib drag - drag

Question

so I'm enrolled in Stanford's Cryptography class on Coursera and I've been struggling with the first programming assignment (I'm a few weeks behind.)
I've been playing around with different variations of this code for a few weeks to try and remove the issues mentioned below...
At first, I thought I was getting a successful crib-drag, but then I realized a multitude of issues, none of which I've been able to solve:
The "deciphered" results were shortening from the wrong end of the word as the crib is dragged across the XOR of the two cipher texts ("The" > "Th" > "T" instead of "The" > "he" > "e")
The result of crib dragging isn't the text of the other message, but the crib itself...in other words, no matter what crib I choose, the first X number of indices ALWAYS return the crib itself
Here's the code:
def string_xor(a, b):
return "".join([chr(ord(x) ^ ord(y)) for (x, y) in zip(a ,b)])
def manual_crib_drag(word):
with open("two_ciphers.txt", "r") as f:
cipher1 = f.readline()
cipher2 = f.readline()
xor = string_xor(cipher1, cipher2)
word_hex = word.encode("hex")
for x in range(len(xor)):
try:
result = string_xor(xor[x:x+len(word_hex)], word_hex)\
.strip().decode("hex")
print x, ":", result
except TypeError, e: print
Here are the results when running manual_crib_drag("The "):
0 : The
1 : The
2 : The
3 : The
4 : The
5 : The
6 : The
7 : The
8 : The
9 : The
10 : The
11 : The
12 : The
13 : The
14 : The
15 : The
16 : The
17 : The
18 : The
19 : The
20 : The
21 : The
22 : The
23 : The
24 : The
25 : The
26 : The
27 : The
28 : The
29 : The
30 : The
31 : The
32 : The
33 : The
34 : The
35 : The
36 : The
37 : The
38 : The
39 : The
40 : The
41 : The
43 : The?
46 : Tcn$
53 : ??S
71 : PN?
80 : CT"#
83 : ?Q?
88 : `n$
94 : P'e<
99 : U??
118 : b}l
123 : Ǹd?
132 : Tokf
138 : X6%
148 : YW0-
155 : ??4d
161 : ???
171 : ??!
173 : ??d1
177 : Uy?G
200 : hm
202 : de*t
218 : Xn q
238 : Ti0:
249 : 4|5!
253 : i?u
258 : ;G+
263 : t?Qq
269 : )?
275 : t??
282 : Z
285 : G?d
313 : sLtU
319 : !9u?
320 : yo
325 : ?kv0
329 : Gx??
331 : Dﺹ?
For completeness, here are the two cipher texts used in the example:
32510bfbacfbb9befd54415da243e1695ecabd58c519cd4bd2061bbde24eb76a19d84aba34d8de287be84d07e7e9a30ee714979c7e1123a8bd9822a33ecaf512472e8e8f8db3f9635c1949e640c621854eba0d79eccf52ff111284b4cc61d11902aebc66f2b2e436434eacc0aba938220b084800c2ca4e693522643573b2c4ce35050b0cf774201f0fe52ac9f26d71b6cf61a711cc229f77ace7aa88a2f19983122b11be87a59c355d25f8e4
32510bfbacfbb9befd54415da243e1695ecabd58c519cd4bd90f1fa6ea5ba47b01c909ba7696cf606ef40c04afe1ac0aa8148dd066592ded9f8774b529c7ea125d298e8883f5e9305f4b44f915cb2bd05af51373fd9b4af511039fa2d96f83414aaaf261bda2e97b170fb5cce2a53e675c154c0d9681596934777e2275b381ce2e40582afe67650b13e72287ff2270abcf73bb028932836fbdecfecee0a3b894473c1bbeb6b4913a536ce4f9b13f1efff71ea313c8661dd9a4ce
And the result of XORing these two cipher texts is:
PRX]
TS\TW]SW\[\VTS\^W[
TVSPZWSQV
[TZ[P\Q[PZRUS[TVTU[ZUQT[][SZRTWV
h
I'm not sure why it's broken into separate lines, but my guess is that it has to do with spaces in the cipher text XOR result...encasing the return of the string_xor function inside of another join, seems to do the trick though, but because it doesn't seem to affect the results of the crib drag, I left it out of the provided code:
" ".join("".join([chr(ord(x) ^ ord(y)) for (x, y) in zip(a ,b)]).split())
I'd appreciate any help! Thanks in advance.

Answer 1

try converting it first to ascii and then do the xor
x = strxor(unhexlify(ciphertexts[0]),unhexlify(target))
print "Ciphertext[0] xor Target\n"
crib = raw_input("Enter Crib:>")
print "Crib\n-->%s<--"%crib
# Crib Drag
for i in range(len(x)):
z = x[i:]
print "\n[%d]"%i
print "%s"%strxor(z,crib)