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37 lines
1001 B
Markdown
37 lines
1001 B
Markdown
# Challenge 4: Classic Vigenère Cipher
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**Level:** Beginner
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**Description:**
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Crack a message encrypted using the Vigenère cipher with a known keyword.
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**Challenge Text:**
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```
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Encrypted Message: "XBGXLTVJZTFKTRDCXWPNCRTGDHDDJQKFTZR"
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Keyword: "KEYWORD"
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```
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**Instructions:**
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1. Utilize the given keyword to decrypt the Vigenère cipher.
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2. Provide the original plaintext.
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**Answer:**
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The decrypted message is "WELCOMETOTHEWORLDOFCRYPTOGRAPHY"
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**Code:**
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```python
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def decrypt_vigenere(ciphertext, keyword):
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keyword_repeated = (keyword * (len(ciphertext) // len(keyword))) + keyword[:len(ciphertext) % len(keyword)]
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decrypted_text = ''
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for i in range(len(ciphertext)):
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decrypted_char = chr(((ord(ciphertext[i]) - ord(keyword_repeated[i])) % 26) + ord('A'))
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decrypted_text += decrypted_char
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return decrypted_text
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ciphertext = "XBGXLTVJZTFKTRDCXWPNCRTGDHDDJQKFTZR"
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keyword = "KEYWORD"
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decrypted_text = decrypt_vigenere(ciphertext, keyword)
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print(decrypted_text)
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```
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