ZenHAX

Free Game Research Forum | Official QuickBMS support | twitter @zenhax | SSL HTTPS://zenhax.com
It is currently Sun Nov 28, 2021 5:29 pm

All times are UTC




Post new topic  Reply to topic  [ 4 posts ] 
Author Message
 Post subject: CRCs
PostPosted: Tue Apr 13, 2021 11:43 pm 
User avatar

Joined: Wed Nov 18, 2020 5:54 pm
Posts: 18
What is a CRC, and what does it do?

_________________
-Garo


Top
   
 Post subject: Re: CRCs
PostPosted: Wed Apr 14, 2021 11:40 am 
Site Admin
User avatar

Joined: Wed Jul 30, 2014 9:32 pm
Posts: 12568
Sort of numeric representation of a sequence of bytes mainly used to quickly check the integrity of the original bytes.
There are many types of implementations.
32bit CRC and checksums were often used in the past.
ZIP archives and TCP/IP packets are two examples of formats that adopt 32bit CRC in them.

Nowadays there is more interest in using hashes rather than 32bit CRC, hashes are longer and more complex limiting the collisions.
MD5 and SHA are hashes.

Hashes are also often used in cryptography (HMAC) for granting security to integrity.

Anyway Google is better than me at explaining these things.


Top
   
 Post subject: Re: CRCs
PostPosted: Wed Apr 14, 2021 12:41 pm 
User avatar

Joined: Wed Nov 18, 2020 5:54 pm
Posts: 18
Google's no fun.

So they check if modified bytes function correctly?

_________________
-Garo


Top
   
 Post subject: Re: CRCs
PostPosted: Thu Apr 15, 2021 1:08 pm 
Site Admin
User avatar

Joined: Wed Jul 30, 2014 9:32 pm
Posts: 12568
Yeah, integrity indeed.
If you have a ZIP file and you edit the raw content of the archived file without changing the CRC, the software will tell you that there is an error in the archive.

But there are also cases where they are used to reference other content without writing that content again, for example there are situations where:
- crc/hash is used to idenfity the filename which is not stored anywhere in the archive, the content of the file will use the crc/hash only
- crc/hash is used to identify a particular string to use in a game and the multi-language content is associated to that crc/hash


Top
   
Display posts from previous:  Sort by  
Post new topic  Reply to topic  [ 4 posts ] 

All times are UTC


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Powered by phpBB® Forum Software © phpBB Limited