46 lines
No EOL
1.5 KiB
Python
46 lines
No EOL
1.5 KiB
Python
def keymat(k):
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k = k.upper().replace('J', 'I')
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seen = set(); seq = []
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for ch in (k + "ABCDEFGHIKLMNOPQRSTUVWXYZ"):
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if ch.isalpha() and ch not in seen:
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seen.add(ch); seq.append(ch)
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return [seq[i:i+5] for i in range(0, 25, 5)]
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def pairs(s, prep=True):
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s = ''.join(ch for ch in s.upper() if ch.isalpha())
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if prep:
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s = s.replace('J', 'I')
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p = []; i = 0
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while i < len(s):
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a = s[i]; b = s[i+1] if i+1 < len(s) else 'X'
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if a == b:
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p.append(a + 'X'); i += 1
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else:
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p.append(a + b); i += 2
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return p
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return [s[i:i+2] for i in range(0, len(s), 2)]
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def playfair(text, key, enc=True):
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m = keymat(key)
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pos = {m[r][c]: (r, c) for r in range(5) for c in range(5)}
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out = []
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for a, b in pairs(text, prep=enc):
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r1, c1 = pos[a]; r2, c2 = pos[b]
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if r1 == r2:
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out.append(m[r1][(c1 + (1 if enc else -1)) % 5] +
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m[r2][(c2 + (1 if enc else -1)) % 5])
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elif c1 == c2:
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out.append(m[(r1 + (1 if enc else -1)) % 5][c1] +
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m[(r2 + (1 if enc else -1)) % 5][c2])
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else:
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out.append(m[r1][c2] + m[r2][c1])
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return ''.join(out)
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enc = lambda pt, k: playfair(pt, k, True)
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dec = lambda ct, k: playfair(ct, k, False)
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if __name__ == '__main__':
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pt = input("Plaintext: ")
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k = input("Key: ")
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ct = enc(pt, k); print("Ciphertext:", ct)
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print("Decrypted:", dec(ct, k)) |