51 lines
1.2 KiB
Python
51 lines
1.2 KiB
Python
import binascii
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import hashlib
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import time
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import re
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from Crypto.Cipher import ARC4
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from .misc import assert_true
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from .keys import EA_KEY
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def new_prng():
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state = 0x41c64e6d
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while True:
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x = (state * 0x838c9cda) + 0x6072
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# state = (state * 0x41c64e6d + 0x3039)
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# state = (state * 0x41c64e6d + 0x3039)
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state = (state * 0xc2a29a69 + 0xd3dc167e) & 0xffffffff
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yield (x & 0x7fff0000) | state >> 15 & 0xffff
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prng = new_prng()
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def validate_key(info):
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match = re.match(r"^(\d)-([0-9a-f]{8})-([0-9a-f]{4})$", info)
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assert_true(match is not None, "Invalid eamuse info key")
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assert match is not None
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version = match.group(1)
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assert_true(version == "1", f"Unsupported encryption version ({version})")
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seconds = binascii.unhexlify(match.group(2)) # 4 bytes
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rng = binascii.unhexlify(match.group(3)) # 2 bytes
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return seconds, rng
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def get_key(prng_=None):
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return f"1-{int(time.time()):08x}-{(next(prng_ or prng) & 0xffff):04x}"
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def ea_symmetric_crypt(data, info):
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seconds, rng = validate_key(info)
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key = hashlib.md5(seconds + rng + EA_KEY).digest()
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return ARC4.new(key).encrypt(data)
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__all__ = ("new_prng", "prng", "validate_key", "get_key", "ea_symmetric_crypt")
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