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Author Topic: [JAVA] How to calculate the cheksum?  (Read 4661 times)

Reipers

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[JAVA] How to calculate the cheksum?
« on: February 16, 2013, 06:39:18 pm »
Hello people! My name is Reinaldo, translate mobile games some years ago here in Brazil. I am currently translating a game called Heroes Lore Zero. It has a folder that contains all items in the game so far could not figure out how to translate these items. I'm with the game in 3 versions: English, Russian and Chinese. Comparing the files, it was found that there is protection through CHECKSUM. In each version there is a checksum that is different in each of the versions. My question is: How to calculate the checksum? The low, see one of the files I'm trying to translate.

Spoiler:

Look in each version the check digit.
English: 8B
Russian: 2A
Chinese: 8C
If anyone knows how to calculate the checksum, please help me. Only that I lack to complete the translation of Heroes Lore Zero to portuguese.

--Moderator edit--
Fixed formatting errors.
« Last Edit: February 16, 2013, 08:45:02 pm by Lenophis »

Bisqwit

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Re: [JAVA] How to calculate the cheksum?
« Reply #1 on: March 12, 2013, 02:48:52 pm »
Your best bet is probably try to trace the ROM code and see how it verifies the sum. Just put a breakpoint at reading the memory address of the checksum, and trace backwards and forwards a bit to see how the variables that the checksum is compared to are calculated.

henke37

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Re: [JAVA] How to calculate the cheksum?
« Reply #2 on: March 12, 2013, 03:19:50 pm »
Looks like it is small enough to brute force. Anyway, it is likely a literal sum if it is just 8 bits.

Bisqwit

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Re: [JAVA] How to calculate the cheksum?
« Reply #3 on: March 12, 2013, 03:29:09 pm »
Likely is not good enough. I already tried that, and it does not match.

FinS

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Re: [JAVA] How to calculate the cheksum?
« Reply #4 on: March 12, 2013, 04:20:42 pm »
Looks like it's just the checksum 8 of the first byte before the item up to the checksum. This also applies to the other items so that is confirmative.


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Re: [JAVA] How to calculate the cheksum?
« Reply #5 on: March 14, 2013, 09:13:10 am »
Looks like it's just the checksum 8 of the first byte before the item up to the checksum. This also applies to the other items so that is confirmative.

Ah, nice. I only tried the parts that the original posted had highlighted. Good catch.

Ridculle

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Re: [JAVA] How to calculate the cheksum?
« Reply #6 on: March 14, 2013, 09:20:51 am »
Looks like it's just the checksum 8 of the first byte before the item up to the checksum. This also applies to the other items so that is confirmative.



By the way, what is your hex editor?
Through dreams I influence mankind

FinS

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Re: [JAVA] How to calculate the cheksum?
« Reply #7 on: March 14, 2013, 08:17:50 pm »
By the way, what is your hex editor?

HxD