DrPepUr's DrPepUr #4
| Download DrPepUr_#4_KeyGenMe.zip, 6 kb (password: crackmes.de) Browse contents of DrPepUr_#4_KeyGenMe.zip Rules
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Solutions
Solution by ORacLE_nJ, published 25. apr, 2010; download (77 kb), password: crackmes.de or browse.
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Discussion and comments
| kcynice 24. Mar 2008 | I tried for a whole day,but I am failed to get the first 4 characters of the serial string. At 00401AF2: call 00401910. It seems like xor encryption. I had enumerate all the possible characters from '0' to 'z'(of course for every character),its strange that i failed too. There are a sequence of call for 00401910,the complexity upgrades! Any advice? Thanks. |
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| DrPepUr Author 24. Mar 2008 | The first 4 bytes are used to make a CRC32 checksum, the easiest way to find them out is by coding a CRC32 brute forcer. |
| kcynice 24. Mar 2008 | I don't know how to write the reverse function and get the original 4 bytes,but i have got it by enumeration,its "DRP-". Your program is very good to practise. I have done all the work. the same issue is my keygen is only can work in debugger. I guess the magic exists at [0040320F],perhaps you use a newer anti-debug tech than last one(#3). I am missed myself this time.btw,i don't to how to code a CRC32 brute forcer. |
| kcynice 24. Mar 2008 | i enumerated all the printable characters no longer than only at '0' to 'z' range.So fortunately! |
| kcynice 25. Mar 2008 | the last issue is its anti-debug stratage,i have not resolved it by now. ....... |
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