160 lines
3.9 KiB
Python
Executable file
160 lines
3.9 KiB
Python
Executable file
#!/usr/bin/python2
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# -*- coding: utf-8 -*-
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import random
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letters = "_abcdefghijklmnopqrstuvwxyz.0123456789,-+*/:?!'()"
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tiles = zip(letters, map(lambda x: (x / 7, x % 7), range(7 * 7)))
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padding_size = 10
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def check_key(key):
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if len(key) != len(letters):
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raise ValueError('Wrong key size')
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cnts = {}
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for c in letters:
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cnts[c] = 0
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for c in key:
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if not c in cnts:
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raise ValueError('Letter ' + c + ' not in LS47!')
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cnts[c] += 1
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if cnts[c] > 1:
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raise ValueError('Letter ' + c + ' duplicated in key!')
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def find_ix(letter):
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m = filter(lambda (l, pos): l == letter, tiles)
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if len(m) != 1:
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raise ValueError('Letter ' + letter + ' not in LS47!')
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for (l, pos) in m:
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return pos
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def find_pos(key, letter):
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p = key.find(letter)
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if p >= 0 and p < 7 * 7:
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return (p / 7, p % 7)
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raise ValueError('Letter ' + letter + ' not in key?!')
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def add_pos((ax, ay), (bx, by)):
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return ((ax + bx) % 7, (ay + by) % 7)
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def sub_pos((ax, ay), (bx, by)):
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return ((ax - bx) % 7, (ay - by) % 7)
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def find_at_pos(key, (row, col)):
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return key[col + row * 7]
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def rotate_right(key, row, n):
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mid = key[7 * row:7 * (row + 1)]
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n = (7 - n % 7) % 7
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return key[:7 * row] + mid[n:] + mid[:n] + key[7 * (row + 1):]
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def rotate_down(key, col, n):
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lines = map(lambda i: key[i * 7:(i + 1) * 7], range(7))
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lefts = map(lambda l: l[:col], lines)
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mids = map(lambda l: l[col], lines)
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rights = map(lambda l: l[col + 1:], lines)
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n = (7 - n % 7) % 7
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mids = mids[n:] + mids[:n]
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return reduce(lambda a, b: a + b, map(lambda i: lefts[i] + mids[i] \
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+ rights[i], range(7)))
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def rotate_marker_right((mrow, mcol), row, n):
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if mrow != row:
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return (mrow, mcol)
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else:
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return (mrow, (mcol + n) % 7)
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def rotate_marker_down((mrow, mcol), col, n):
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if mcol != col:
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return (mrow, mcol)
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else:
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return ((mrow + n) % 7, mcol)
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def derive_key(password):
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i = 0
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k = letters
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for c in password:
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(row, col) = find_ix(c)
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k = rotate_down(rotate_right(k, i, col), i, row)
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i = (i + 1) % 7
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return k
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def encrypt(key, plaintext):
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check_key(key)
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mp = (0, 0)
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ciphertext = ''
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for p in plaintext:
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pp = find_pos(key, p)
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mix = find_ix(find_at_pos(key, mp))
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cp = add_pos(pp, mix)
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c = find_at_pos(key, cp)
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ciphertext += c
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key = rotate_right(key, pp[0], 1)
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mp = rotate_marker_right(mp, pp[0], 1)
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cp = find_pos(key, c)
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key = rotate_down(key, cp[1], 1)
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mp = rotate_marker_down(mp, cp[1], 1)
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mp = add_pos(mp, find_ix(c))
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return ciphertext
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def decrypt(key, ciphertext):
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check_key(key)
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mp = (0, 0)
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plaintext = ''
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for c in ciphertext:
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cp = find_pos(key, c)
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mix = find_ix(find_at_pos(key, mp))
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pp = sub_pos(cp, mix)
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p = find_at_pos(key, pp)
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plaintext += p
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key = rotate_right(key, pp[0], 1)
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mp = rotate_marker_right(mp, pp[0], 1)
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cp = find_pos(key, c)
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key = rotate_down(key, cp[1], 1)
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mp = rotate_marker_down(mp, cp[1], 1)
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mp = add_pos(mp, find_ix(c))
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return plaintext
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def encrypt_pad(key, plaintext, signature):
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# TODO it would also be great to randomize the message length.
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check_key(key)
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padding = ''.join(map(lambda x: letters[random.randint(0,
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len(letters) - 1)], range(padding_size)))
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return encrypt(key, padding + plaintext + '---' + signature)
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def decrypt_pad(key, ciphertext):
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check_key(key)
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return decrypt(key, ciphertext)[padding_size:]
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if __name__ == '__main__':
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# a bit of test!
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key = derive_key('s3cret_p4ssw0rd/31337')
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print 'key:', key
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enc = encrypt_pad(key, 'conflagrate_the_rose_bush_at_six!',
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'peace-vector-3')
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print 'encrypted:', enc
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dec = decrypt_pad(key, enc)
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print 'decrypted:', dec
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