/vigen.py Secret
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December 15, 2015 14:09
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#!/usr/bin/env python2 | |
# -*- coding: utf-8 -*- | |
# vim: set fileencoding=UTF-8 : | |
''' | |
Vigenère Cipher implementation by Michael Yanovich (aka: yano) | |
Copyright 2013 - Licensed under the Eiffel Forum License v2 | |
USAGE: | |
./vigen.py KEY | |
Enter text to be mangled: I LIKE CHEESE | |
Offset: 0 | |
Encrypted: S PGUI ARICCI | |
''' | |
import math | |
import sys | |
import string | |
alpha = string.lowercase | |
try: | |
KEY = sys.argv[1] | |
except: | |
print 'Please run as ./vigen.py KEY_HERE' | |
sys.exit(1) | |
incoming = raw_input('Enter text to be mangled: ') | |
try: | |
offset = int(raw_input('Offset: ')) | |
except: | |
print 'The offset was not a number!' | |
sys.exit(1) | |
## default to an offset of 1 if none provided | |
if not offset: | |
offset = 1 | |
## subtract 1 so it works with python's 0's index for lists | |
## this part actually broke it, and ended up making it a ROT12 | |
## when it should have been a ROT13 | |
#offset -= 1 | |
## generate the Vigenère square shading | |
chart = dict() | |
k = 0 | |
for letter in alpha: | |
if k + offset >= len(alpha): | |
## rotation won't go beyond end of row | |
sanit = k + offset - len(alpha) | |
chart[letter] = alpha[sanit:] + alpha[:sanit] | |
else: | |
## rotation goes beyond the end of the row | |
chart[letter] = alpha[k + offset:] + alpha[:k + offset] | |
k += 1 | |
## display the chart to stdout | |
ordered_rows = chart.keys() | |
ordered_rows.sort() | |
for x in ordered_rows: | |
print x, chart[x] | |
print '' | |
## pad the key with the length of the incoming text | |
multi = math.ceil(len(incoming) / float(len(KEY))) | |
long_key = KEY * int(multi) | |
## encrypted the incoming text | |
j = 0 | |
output_encrypted = str() | |
for x in incoming: | |
y = x.lower() | |
if y in chart: | |
row = chart[y] | |
idx = (string.lowercase).find(long_key[j].lower()) | |
output_encrypted += chart[y][idx] | |
j += 1 | |
else: | |
output_encrypted += y | |
## decrypt the incoming text | |
p = 0 | |
output_decrypted = str() | |
for x in incoming: | |
y = x.lower() | |
stop = False | |
before = len(output_decrypted) | |
for letter in chart: | |
row = chart[letter] | |
if not stop and y in chart: | |
idx = (string.lowercase).find(long_key[p].lower()) | |
if row[idx] == y: | |
output_decrypted += letter | |
p += 1 | |
stop = True | |
after = len(output_decrypted) | |
if before == after: | |
output_decrypted += y | |
print 'Encrypted:', output_encrypted.upper() | |
print 'Decrypted:', output_decrypted.upper() |
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