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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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