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Cps2 emulator youtube4/2/2024 ![]() This means that only 4 (E,D) pairs are needed to isolate the key.Īlso, I made several important optimisations that I missed the first time around, like caching intermediate results and speeding up the s-boxes calculations by using precalculated tables (this last optimisation also made into MAME so the decryption when loading a game is now faster). I therefore rewrote the program to take that into account. However, now we know that the key actually has only 64 significant bits, some of which are repeated. One can find hundreds, even thousands of of (E,D) pairs, but if they are not at compatible addresses they are of no use to find the key using this attack. For the Super Puzzle Fighter 2 games, the range is just 0x40000 bytes, giving just 2 pairs per address. This is a serious limitation, because the code of several games only covers a range of 0x80000 bytes, which would give a maximum of 4 pairs at any address. Remember that they must be at compatible addresses, that is addresses whose bottom 17 bits are the same. ![]() When I originally wrote the key searching program, that was on the assumption that the key for the second Feistel network was 96 bits long.Įach (E,D) pair reduces the key space by a factor of about 2 16, so to isolate the correct key with good confidence one would need at least 96/16 = 6 (E,D) pairs.
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