NewBase64 [200pts] - Cryptography Write-up#

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def char_gen():
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    char = [chr(i) for i in range(ord('ก'), ord('ก') + 47)]
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    char += [chr(i) for i in range(ord('๐'), ord('๐') + 10)]
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    char += [chr(i) for i in range(ord('0'), ord('0') + 10)]
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    char = char[:64]
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    return char
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def char_to_hex(msg):
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    hex_data = ''
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    for c in msg.encode():
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        hex_data += hex(c)[2:]
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    return hex_data
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def base64_encode(msg):
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    char = char_gen()
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    msg = char_to_hex(msg)
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    msg_num = eval('0x' + msg)
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    base64 = ''
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    while msg_num > 0:
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        base64 = char[msg_num % 64] + base64
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        msg_num = msg_num // 64
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    base64 += '=='
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    return base64
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msg = input('Message: ')
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base64 = base64_encode(msg)
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open('enc.txt', 'wb').write(base64.encode('utf-16'))

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ฒ๗4๐บฃขหผ๗ฉยฉจฒษปธญมปธญมพงยฦฉงบอนทฝมบว4๓ฉจฦ๐พณขวผงฆศฟ๗ฝ๑ญงฒภปฤขรธ๘ฒษญธฎภญธฎภพงม๔ธ๗๙๔พ๖4ฃฑจฎฦฎฤฒภฎฤฑ๑ญคก๗ฎคก๑ญจ๕มฉณฅยฉ๓ญฤ==

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def make_alphabet():
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    chars = [chr(i) for i in range(ord('ก'), ord('ก') + 47)]   # ก... (47 ตัว)
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    chars += [chr(i) for i in range(ord('๐'), ord('๐') + 10)]  # ๐-๙ (10 ตัว)
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    chars += [chr(i) for i in range(ord('0'), ord('0') + 10)]  # 0-9 (10 ตัว)
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    return chars[:64]
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ALPHABET = make_alphabet()
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ALPH2VAL = {c: i for i, c in enumerate(ALPHABET)}
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def custom64_to_int(s):
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    value = 0
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    for ch in s:
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        if ch not in ALPH2VAL:
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            raise ValueError(f"Alphabet NOT FOUND IN: {ch!r}")
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        value = value * 64 + ALPH2VAL[ch]
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    return value
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def decode_custom_base64(enc_text):
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    if enc_text.endswith("=="):
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        enc_text = enc_text[:-2]
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    n = custom64_to_int(enc_text)
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    hex_str = format(n, "x")
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    if len(hex_str) % 2 == 1:
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        hex_str = "0" + hex_str
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    data = bytes.fromhex(hex_str)
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    return data.decode("utf-8", errors="replace")
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if __name__ == "__main__":
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    import pathlib
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    enc_path = pathlib.Path("enc.txt")
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    enc_text = enc_path.read_text(encoding="utf-16").strip()
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    result = decode_custom_base64(enc_text)
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    print(result)