81 lines
No EOL
2.4 KiB
Python
81 lines
No EOL
2.4 KiB
Python
def generate_playfair_matrix(key):
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key = ''.join(sorted(set(key.upper()), key=key.upper().index))
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alphabet = "ABCDEFGHIKLMNOPQRSTUVWXYZ" # J omitted
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unique = []
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for ch in key:
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if ch != 'J' and ch not in unique:
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unique.append(ch)
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for ch in alphabet:
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if ch not in unique:
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unique.append(ch)
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return [unique[i:i+5] for i in range(0, 25, 5)]
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def find_pos(matrix, char):
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for row_idx, row in enumerate(matrix):
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if char in row:
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col_idx = row.index(char)
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return row_idx, col_idx
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return None
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def prepare_text(text):
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text = ''.join(ch for ch in text.upper() if ch.isalpha()).replace('J', 'I')
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pairs, i = [], 0
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while i < len(text):
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if i + 1 < len(text) and text[i] != text[i + 1]:
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pairs.append(text[i:i + 2])
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i += 2
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else:
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pairs.append(text[i] + 'X')
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i += 1
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return pairs
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def playfair_en(ptext, pfk):
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matrix = generate_playfair_matrix(pfk)
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ptext_pairs = prepare_text(ptext)
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ctext = []
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for pair in ptext_pairs:
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r1, c1 = find_pos(matrix, pair[0])
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r2, c2 = find_pos(matrix, pair[1])
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if r1 == r2:
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ctext.append(matrix[r1][(c1 + 1) % 5] + matrix[r2][(c2 + 1) % 5])
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elif c1 == c2:
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ctext.append(matrix[(r1 + 1) % 5][c1] + matrix[(r2 + 1) % 5][c2])
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else:
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ctext.append(matrix[r1][c2] + matrix[r2][c1])
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return ''.join(ctext)
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def playfair_de(ctext, pfk):
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matrix = generate_playfair_matrix(pfk)
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ctext_pairs = prepare_text(ctext)
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ptext = []
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for pair in ctext_pairs:
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r1, c1 = find_pos(matrix, pair[0])
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r2, c2 = find_pos(matrix, pair[1])
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if r1 == r2:
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ptext.append(matrix[r1][(c1 - 1) % 5] + matrix[r2][(c2 - 1) % 5])
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elif c1 == c2:
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ptext.append(matrix[(r1 - 1) % 5][c1] + matrix[(r2 - 1) % 5][c2])
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else:
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ptext.append(matrix[r1][c2] + matrix[r2][c1])
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return ''.join(ptext)
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def main():
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ptext = input("Kindly enter your desired plaintext: ")
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pfk = input("Kindly enter the Playfair Key: ")
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print("Welcome to the Playfair cipher system.")
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print("Plaintext: ", ptext)
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print("Playfair Key: ", pfk)
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ctext = playfair_en(ptext, pfk)
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print("Ciphertext: ", ctext)
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decrypted_text = playfair_de(ctext, pfk)
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print("Decrypted Text: ", decrypted_text)
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if __name__ == '__main__':
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main() |