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crack_xor.py
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crack_xor.py
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import string
import sys
import base64
import binascii
import matplotlib.pyplot as plt
import math
import json
import langdetect
def single_byte_xor(a, b):
result = ""
for i in range(len(a)):
result += chr(ord(a[i]) ^ b)
return result
def score_key(freq, lang):
score = 0.0
for i in range(256):
try:
score += freq[i]*lang[str(i)]
except KeyError:
score += 0.0
return score
def crack_single_byte_xor(cipher, lang):
score = []
for i in range(256):
decoded = single_byte_xor(cipher, i)
freq = get_sym_freq(decoded)
score.append(score_key(freq, lang))
print "Key: " + str(i) + " Score: " + str(score[i])
if all(ord(char) < 128 for char in decoded):
try:
print "Probable language: " + str(langdetect.detect(decoded))
print decoded
except:
print "No language detected."
print min(score)
return
def get_sym_freq(data):
table = dict()
for i in range(256):
table[i] = 0.
for char in data:
table[ord(char)] += 1
for i in range(256):
table[i] /= len(data)
return table
def main():
with open('single-byte-xor-cipher', 'r') as f:
data = binascii.unhexlify(f.read().rstrip())
with open('engl_letter_freq.json', 'r') as f:
letter_freq_engl = json.load(f)
crack_single_byte_xor(data.rstrip(), letter_freq_engl)
if __name__ == '__main__':
main()