def decode():
standard_frequency = Frequency.get(Util.FILE_NAME)
text_frequency = standard_frequency.fromkeys(standard_frequency.keys(), float(0))
file = open(Util.ENCODED_FILE, "r")
numchar = 0
c = file.read(1)
while c != '':
o = ord(c)
if o in range(65, 90):
o = o + 32
if o in range(97, 122):
c = chr(o)
text_frequency[c] = text_frequency[c] + 1
numchar = numchar + 1
c = file.read(1)
file.close()
for f in text_frequency:
text_frequency[f] = 100 * text_frequency[f] / numchar
#print f, text_frequency[f]
sorted_standard_frequency = sorted(standard_frequency.items(), key=operator.itemgetter(1), reverse=True)
sorted_text_frequency = sorted(text_frequency.items(), key=operator.itemgetter(1), reverse=True)
#print sorted_standard_frequency
#print sorted_text_frequency
keys = []
list_index = 0
index_key = 0
while index_key == 0:
standard_character, standard_value = sorted_standard_frequency[0]
text_character, text_value = sorted_text_frequency[list_index]
list_index = list_index + 1
standard_ascii = ord(standard_character)
text_ascii = ord(text_character)
key_value = text_ascii - standard_ascii
if key_value < 0:
key_value = key_value + 26
found_key = False
for key, key_confidence in keys:
if key_value == key:
found_key = True
if not found_key:
keys.insert(len(keys), (key_value, 0))
key_value, key_confidence = keys[len(keys) - 1]
for f in sorted_text_frequency:
text_character, text_value = f
decodedKey = ord(text_character) - key_value
if decodedKey < 97:
decodedKey = decodedKey + 26
standard_character, standard_value = sorted_standard_frequency[sorted_text_frequency.index(f)]
if (standard_character == chr(decodedKey)):
key_confidence = key_confidence + text_value
keys[len(keys) - 1] = (key_value, key_confidence)
for k in keys:
value, confidence = k
print keys.index(k)+1 ,". Encryption key: ", value, ", confidence value: ", confidence, "."
while True:
input_key = raw_input("Select a key or type 0 to calculate another key -> ")
try:
index_key = int(input_key)
if (index_key >= 1) and (index_key <= len(keys)):
key_value, key_confidence = keys[index_key - 1]
break
else:
if (index_key == 0) and (list_index < len(sorted_standard_frequency)):
print "Calculating another key..."
break
else:
if index_key == 0:
print "All keys have been already generated!"
else:
print "Key index incorrect!"
except Exception as e:
print "Key index incorrect, please insert a number!"
file = open(Util.ENCODED_FILE, "r")
decrypted = open(Util.DECODED_FILE, "w")
encoded_character = file.read(1)
while encoded_character != '':
ascii = ord(encoded_character)
decoded_character = ascii
if (ascii >= 65 and ascii <= 90) or (ascii >= 97 and ascii <= 122):
decoded_character = ascii - key_value
if decoded_character < 65:
decoded_character = decoded_character + 26
if decoded_character < 97 and (ascii >= 97 and ascii <= 122):
decoded_character = decoded_character + 26
decrypted.write(chr(int(decoded_character)))
encoded_character = file.read(1)
decrypted.close()
file.close()
