[Botan-devel] Calculating CRC32

jose jimenez j.jimenez25 at yahoo.com.mx
Wed Jan 13 17:34:32 EST 2010


Hi. thanks for the quick answer.
the source code of the application is the file "checksum.cpp" found under the 'doc/Examples' folder from botan 1.8.8. I didnt change anything. just compiled and run.
the md5 test I made where using the file '/doc/example/hash.cpp' again nothing changed. my concern is that I tested the the md5 hashes of a file using several diferent applications and again the result was inconsistent with botan.
my concern is that when i compiled the .lib there was something wrong with cpu endians.. don't know really just being paranoid.
so. if somebody will be so kind to get the md5 and crc32 of the following file. so i can check if it is the same result i get. i could move on knowing that my build is ok.
CRC32:FC97D8B8md5:C1216B4F2CBFD02392BBF12DBDB17345File: http://rapidshare.com/files/334878052/mt.dep.html



thanks in advance.


Message: 1
Date: Tue, 12 Jan 2010 16:26:45 -0800 (PST)
From: jose jimenez <j.jimenez25 at yahoo.com.mx>
To: botan-devel at randombit.net
Subject: [Botan-devel] Calculating crc32
Message-ID: <466748.11522.qm at web57401.mail.re1.yahoo.com>
Content-Type: text/plain; charset="iso-8859-1"

Hi folks. I just discovered botan and I just have to say that is awesome.
I recently download and built the latest stable release: 1.8.8 and compiled it with visual studio 2005 profesional. suing /MD and /MDd switches for debug version.
everything copiles,links and runs fine. but I noticed something weird.
I compiled the 'checksum' example. and run it without any problems. the thing is... that the CRC32 reported by the example is diferent than the one reported by Winrar/Winzip etc. this is also true for md5 hashes.
if you want to see what i'm talking about. please check the following linkhttp://rapidshare.com/files/331301241/ChecksumExample.rar.html
it has the compiled checksum.exe, and also my test file.?thanks in advance



Message: 2
Date: Tue, 12 Jan 2010 20:30:53 -0500
From: Jack Lloyd <lloyd at randombit.net>
To: botan-devel at randombit.net
Subject: Re: [Botan-devel] Calculating crc32
Message-ID: <20100113013053.GN24196 at randombit.net>
Content-Type: text/plain; charset=us-ascii

On Tue, Jan 12, 2010 at 04:26:45PM -0800, jose jimenez wrote:

> I compiled the 'checksum' example. and run it without any
> problems. the thing is... that the CRC32 reported by the example is
> diferent than the one reported by Winrar/Winzip etc. this is also
> true for md5 hashes.

There are many different 32-bit CRCs [1], and it is possible Zip uses
a different one; I took a look at various docs but could not find
anything about that one way or another. The CRC32 in botan is the IEEE
802.3 Ethernet CRC, which is probably the most common.

However if MD5 hashes are also off, it is likely the problem is that
the Zip/RAR formats only include a portion of the data (for instance
just the plain file data and not the metadata headers - I know next to
nothing about the Zip/RAR formats so that's just an example of one
reason why the checksums you are calculating aren't matching the
values in the file).

Unfortunately the .exe isn't of much use for me in terms of debugging,
both because I mostly run Linux or other Unices, and because without
source it's really hard to see what exactly is going on.

-Jack

[1] http://en.wikipedia.org/wiki/Cyclic_redundancy_check#Commonly_used_and_standardized_CRCs


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