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challenge1-4.py
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challenge1-4.py
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import binascii
from Crypto.Util.strxor import strxor_c
# From http://www.data-compression.com/english.html
freqs = {
'a': 0.0651738,
'b': 0.0124248,
'c': 0.0217339,
'd': 0.0349835,
'e': 0.1041442,
'f': 0.0197881,
'g': 0.0158610,
'h': 0.0492888,
'i': 0.0558094,
'j': 0.0009033,
'k': 0.0050529,
'l': 0.0331490,
'm': 0.0202124,
'n': 0.0564513,
'o': 0.0596302,
'p': 0.0137645,
'q': 0.0008606,
'r': 0.0497563,
's': 0.0515760,
't': 0.0729357,
'u': 0.0225134,
'v': 0.0082903,
'w': 0.0171272,
'x': 0.0013692,
'y': 0.0145984,
'z': 0.0007836,
' ': 0.1918182
}
def score(s):
score = 0
for c in s:
if c in freqs:
score += freqs[c]
# print score
return score
def check(s):
check_string =s;
max_val=0
pos =0;
for i in range(0,256):
res = strxor_c(check_string, i)
temp =score(res)
if temp > max_val:
max_val=temp
pos =i
return pos,max_val,check_string
f_in= open("file1-4.txt",'r')
f_out = open("ans.txt",'w')
final_max = 0
final_pos =0
final_string =""
for line in f_in:
line= line.strip()
s = line.decode('hex')
pos,max_val,fin = check(s)
if max_val> final_max:
final_max = max_val
final_pos =pos
final_string = fin
print final_max, final_pos , strxor_c(final_string,final_pos)