a newbie question about CRC32
 

how can we patch a program protected with CRC32.. is there any tools out thier can remove this kind of protection .. please help..

CRC32 is not a protection itself but simply checksum algorithm.

If you have found that your soft uses CRC32 and don't know how to locate and eliminate the verification code then I suggest to use a loader instead of patching.

thankz for your reply dyn!o .. I used (Krypto ANALyzer) which list this thing

CRC32::00191B68::00593168
|-Referenced at 00481C8C
|-Referenced at 00481CAC
|-Referenced at 00481CC7
|-Referenced at 00481CE3
|-......................

if that what you ment by locating the code Now what the next step.. to eliminate the verification code..

best regards..

Read the article "CRC and how to Reverse it" by Anarchriz/DREAD
_http://www.xs4all.nl/~koekeroe/hacked/crc.htm
If you find where CRCvalue is stored in your program you could change it to required value after program patching.

Thankz a lot Sergey R. ..it is such along essay thoo :D

sorry.. but it seems hard to understand ....is there a tool to remove or recalculate or correct CRC32 for me.. I appreciated your help

use PEiD CRC32 Plugin

thankz alot for your reply MaRKuS-DJM .. could you please explain what you mean..

I used (Krypto ANALyzer) which list this information

CRC32::00191B68::00593168
|-Referenced at 00481C8C
|-Referenced at 00481CAC
|-Referenced at 00481CC7
|-Referenced at 00481CE3
|-......................

now what next..I realy appreciated your help..

abccc,

in my page, you can find a tool called crc48fix.zip, that allow you make any file match a given crc16, 32 and 48

vecna

It might help if you said "where" your page might be found.

Regards,

jmi,

its in my user profile in the board. i thought it show up in my post. anyway, its at http://infamy.host.sk

vecna/29a

qwerty3 and ancev:

ancev:

It is always good to acknowledge one's own errors and learn from them, if that is possibe. ancev I did look at your profile here, but forgot to look at the entire page and didn't see the "home page" which was clearly listed. So the best I can say for myself is "Well duh!" :D

Actually, I really wasn't looking for the file CRC48fix.zip itself, because, strangely enough, I had actually downloaded it from that Woodmann post back in 2002. I was trying to find a location for others who might have been interested, because I didn't remember "where" I had gotten it and I didn't want to add an attachment if the place to download could be easily found. As you may know, I am a Moderator there also and make a habit of downloading all the attachments that look even slightly interesting, and I also have copies of all of them in the backups of the Board.

However it is curious that your google search turned up that thread and my own, both before I posted and just again now, turns up nothing. I have noticed, in conversation with some members of the Woodmann Forum that those using "google" searches in other countries do obtain different result than what I receive here is the U.S. Don't know if that is the issue or if you said "google" and may actually have used some "other" seach engine. But it still isn't showing up here. Dont' know why it works for you and I get nothing at all. :confused:

Regards,

I found a nice tool PEiD CRC32 Plugin (thanks MaRKuS-DJM )

hxxp://www.secretashell.com/codomain/peid/plugins/crc32-gelios.zip

can anybody tell me where from to get new crc..

regards

CRC links:
http://www.gweep.net/~prefect/eng/reference/crc_v3.txt
http://www.repairfaq.org/filipg/LINK/F_crc_v3.html
http://www.ross.net/crc/links.html