cipher: add scytale cipher

ciphers/columnar_transposition_cipher.py

@@ -0,0 +1,74 @@
+import math
+
+
+def encrypt_columnar_cipher(message: str, key: str) -> str:
+    """
+    Encrypts a message using the Columnar Transposition Cipher.
+
+    :param message: Text to encrypt.
+    :param key: String key used to define column order.
+    :return: Encrypted message.
+    """
+    # Remove spaces and calculate dimensions
+    message = message.replace(" ", "")
+    num_cols = len(key)
+    num_rows = math.ceil(len(message) / num_cols)
+
+    # Fill the grid with characters
+    grid = [""] * num_cols
+    for i, char in enumerate(message):
+        grid[i % num_cols] += char
+
+    # Sort columns based on the key order
+    sorted_key_indices = sorted(range(len(key)), key=lambda k: key[k])
+    ciphertext = "".join([grid[i] for i in sorted_key_indices])
+
+    return ciphertext
+
+
+def decrypt_columnar_cipher(ciphertext: str, key: str) -> str:
+    """
+    Decrypts a message encrypted with the Columnar Transposition Cipher.
+
+    :param ciphertext: Encrypted text.
+    :param key: String key used to define column order.
+    :return: Decrypted message.
+    """
+    num_cols = len(key)
+    num_rows = math.ceil(len(ciphertext) / num_cols)
+    num_shaded_boxes = (num_cols * num_rows) - len(ciphertext)
+
+    # Sort columns based on the key order
+    sorted_key_indices = sorted(range(len(key)), key=lambda k: key[k])
+    col_lengths = [num_rows] * num_cols
+    for i in range(num_shaded_boxes):
+        col_lengths[sorted_key_indices[-(i + 1)]] -= 1
+
+    # Distribute ciphertext into columns based on the sorted key
+    grid = []
+    start = 0
+    for col_length in col_lengths:
+        grid.append(ciphertext[start : start + col_length])
+        start += col_length
+
+    # Rebuild plaintext row by row
+    plaintext = ""
+    for i in range(num_rows):
+        for j in range(num_cols):
+            if i < len(grid[sorted_key_indices[j]]):
+                plaintext += grid[sorted_key_indices[j]][i]
+
+    return plaintext
+
+
+# Example usage
+message = "HELLO WORLD FROM COLUMNAR"
+key = "3412"
+
+# Encrypt the message
+encrypted = encrypt_columnar_cipher(message, key)
+print("Encrypted:", encrypted)
+
+# Decrypt the message
+decrypted = decrypt_columnar_cipher(encrypted, key)
+print("Decrypted:", decrypted)

ciphers/scytale_cipher.py

@@ -0,0 +1,59 @@
+def encrypt_scytale_cipher(message: str, key: int) -> str:
+    """
+    Encrypts a message using the Scytale Cipher.
+
+    :param message: Text to encrypt.
+    :param key: Number of rows (key).
+    :return: Encrypted message.
+    """
+    message = message.replace(" ", "")  # Optional: remove spaces
+    ciphertext = [""] * key
+
+    # Distribute characters across rows based on the key
+    for i in range(len(message)):
+        ciphertext[i % key] += message[i]
+
+    return "".join(ciphertext)
+
+
+def decrypt_scytale_cipher(ciphertext: str, key: int) -> str:
+    """
+    Decrypts a message encrypted with the Scytale Cipher.
+
+    :param ciphertext: Encrypted text.
+    :param key: Number of rows (key).
+    :return: Decrypted message.
+    """
+    num_cols = -(-len(ciphertext) // key)  # Calculate number of columns (round up)
+    num_rows = key
+    num_shaded_boxes = (num_cols * num_rows) - len(ciphertext)  # Extra unused boxes
+
+    plaintext = [""] * num_cols
+    col = 0
+    row = 0
+
+    # Rebuild the plaintext row by row
+    for char in ciphertext:
+        plaintext[col] += char
+        col += 1
+        # Reset column and move to next row if end of column is reached
+        if (col == num_cols) or (
+            col == num_cols - 1 and row >= num_rows - num_shaded_boxes
+        ):
+            col = 0
+            row += 1
+
+    return "".join(plaintext)
+
+
+# Example usage
+message = "HELLO WORLD FROM SCYTALE"
+key = 5
+
+# Encrypt the message
+ciphered = encrypt_scytale_cipher(message, key)
+print("Encrypted:", ciphered)
+
+# Decrypt the message
+deciphered = decrypt_scytale_cipher(ciphered, key)
+print("Decrypted:", deciphered)