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Implement modified vigenere cipher for all printable ASCII #13452
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98b78ed
Implement modified vigenere cipher for all printable ASCII
Abheelash-Mishra baecafe
Improve docstrings
Abheelash-Mishra e371c10
Add more doctests
Abheelash-Mishra 1c84740
Merge branch 'master' into add_printable_ascii_vigenere_cipher
cclauss f30bbab
updating DIRECTORY.md
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,103 @@ | ||
| """ | ||
| This program encrypts or decrypts messages using a modified Vigenere cipher | ||
| that operates on all printable ASCII characters (from 32-126) instead of just letters. | ||
| Each character in the message is shifted by a value derived from the corresponding | ||
| character in the key. When the end of the key is reached, it repeats cyclically. | ||
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| Algorithm summary: | ||
| - For each printable character: | ||
| * Convert both the message and key characters to their ASCII codes. | ||
| * During encryption: add the key's ASCII value to the message character. | ||
| * During decryption: subtract the key's ASCII value from the message character. | ||
| * Wrap the result within the printable ASCII range using modulo arithmetic. | ||
| - Non-printable characters are left unchanged. | ||
| - The key repeats automatically to match the message length. | ||
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| Reference: https://stackoverflow.com/questions/28182091/ascii-vigenere-cipher-implementation-in-java | ||
| """ | ||
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| PRINTABLE_START = 32 | ||
| PRINTABLE_END = 126 | ||
| PRINTABLE_RANGE = PRINTABLE_END - PRINTABLE_START + 1 | ||
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| def encrypt_message(key: str, message: str) -> str: | ||
| """ | ||
| Encrypts a message using printable ASCII Vigenere cipher. | ||
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||
| >>> encrypt_message('key', 'Hello!') | ||
| "Tk'xu;" | ||
| >>> encrypt_message('SUpeR$eCR3t_KEY', 'This is a message to encrypt.') | ||
| 'H^zyr.ycTS#e_Y[[[1zbDkRVF/p`s' | ||
| """ | ||
| return translate_message(key, message, "encrypt") | ||
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| def decrypt_message(key: str, message: str) -> str: | ||
| """ | ||
| Decrypts a message using printable ASCII Vigenere cipher. | ||
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||
| >>> decrypt_message('key', "Tk'xu;") | ||
| 'Hello!' | ||
| >>> decrypt_message('SUpeR$eCR3t_KEY', 'H^zyr.ycTS#e_Y[[[1zbDkRVF/p`s') | ||
| 'This is a message to encrypt.' | ||
| """ | ||
| return translate_message(key, message, "decrypt") | ||
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| def translate_message(key: str, message: str, mode: str) -> str: | ||
| """ | ||
| Translates (encrypts or decrypts) a message using the given key. | ||
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| >>> translate_message('key', 'Hello!', 'encrypt') | ||
| "Tk'xu;" | ||
| >>> translate_message('key', "Tk'xu;", 'decrypt') | ||
| 'Hello!' | ||
| """ | ||
| translated = [] | ||
| key_index = 0 | ||
| key_bytes = [ord(ch) for ch in key] | ||
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||
| for symbol in message: | ||
| sym_val = ord(symbol) | ||
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| if PRINTABLE_START <= sym_val <= PRINTABLE_END: | ||
| key_val = key_bytes[key_index] | ||
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| if mode == "encrypt": | ||
| new_val = ( | ||
| sym_val - PRINTABLE_START + key_val | ||
| ) % PRINTABLE_RANGE + PRINTABLE_START | ||
| elif mode == "decrypt": | ||
| new_val = ( | ||
| sym_val - PRINTABLE_START - key_val | ||
| ) % PRINTABLE_RANGE + PRINTABLE_START | ||
| else: | ||
| raise ValueError("Mode must be 'encrypt' or 'decrypt'") | ||
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| translated.append(chr(new_val)) | ||
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| key_index = (key_index + 1) % len(key_bytes) | ||
| else: | ||
| translated.append(symbol) | ||
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| return "".join(translated) | ||
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| if __name__ == "__main__": | ||
| message = input("Enter message: ") | ||
| key = input("Enter secret key: ") | ||
| mode = input("Encrypt/Decrypt [e/d]: ") | ||
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| if mode.lower().startswith("e"): | ||
| mode = "encrypt" | ||
| translated = encrypt_message(key, message) | ||
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| print(f"Encrypted message: {translated}") | ||
| elif mode.lower().startswith("d"): | ||
| mode = "decrypt" | ||
| translated = decrypt_message(key, message) | ||
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| print(f"Decrypted message: {translated}") | ||
| else: | ||
| print("Invalid mode. Use 'e' or 'd'.") | ||
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