mirror of https://github.com/dirtbags/moth.git
49 lines
1.5 KiB
Python
49 lines
1.5 KiB
Python
#!/usr/bin/python3
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plaintext = [b"This may seem relatively simple, but it's the same basic "
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b"principles as used in s-boxes, a technique used in many modern "
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b"cryptographic algoritms. Of course, instead of letter substitution, "
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b"you're doing byte substitution.",
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b"The next two puzzles are a bit different; Frequency counts (of characters) "
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b"will just reveal random noise. "
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b"Oh, by the way, the key this time is: 'the s is for sucks'."]
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key = b"thequickbrownfxjmpdvlazygs"
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def encode(text):
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ukey = key.upper()
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lkey = key.lower()
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assert len(set(key)) == 26, 'invalid key'
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assert key.isalpha(), 'non alpha character in key'
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out = bytearray()
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for t in text:
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if t in lkey:
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out.append(lkey[t - ord('a')])
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elif t in ukey:
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out.append(ukey[t - ord('A')])
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else:
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out.append(t)
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return bytes(out)
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def decode(text):
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ukey = key.upper()
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lkey = key.lower()
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assert len(set(key)) == 26, 'invalid key'
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assert key.isalpha(), 'non alpha character in key'
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out = bytearray()
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for t in text:
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if t in lkey:
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out.append(ord('a') + lkey.index(bytes([t])))
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elif t in ukey:
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out.append(ord('A') + ukey.index(bytes([t])))
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else:
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out.append(t)
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return bytes(out)
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c = encode(plaintext[0])
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print('<dl><dt>Alice<dd>', str(c, 'utf-8'))
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assert decode(c) == plaintext[0]
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c = encode(plaintext[1])
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print('<dt>Bob<dd>', str(c, 'utf-8'), '</dl>')
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assert decode(c) == plaintext[1]
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