[program-l] Re: Text file checksum code
- From: "George Bell" <george@xxxxxxxxxxxxxxxxxxx>
- To: <program-l@xxxxxxxxxxxxx>
- Date: Wed, 25 Mar 2009 12:57:25 -0000
It's your age, Mark! :-)
George.
-----Original Message-----
From: program-l-bounce@xxxxxxxxxxxxx
[mailto:program-l-bounce@xxxxxxxxxxxxx] On Behalf Of Mark Long
Sent: 25 March 2009 11:55
To: program-l@xxxxxxxxxxxxx
Subject: [program-l] Re: Text file checksum code
I agree. I would use 2 hashes, MD5 and sha1. You can force a collision
with
MD5 but with MD5 and sha1 at the same time? Practically impossible.
Hang on... Did I just agree with Tyler? <grin>
--------------------------------------------------
From: "Tyler Littlefield" <tyler@xxxxxxxxxxxxx>
Sent: Wednesday, March 25, 2009 11:33 AM
To: <program-l@xxxxxxxxxxxxx>
Subject: [program-l] Re: Text file checksum code
> hello,
> while that works, I recommend not using md5. Could use something a
bit
> higher in strength, but that's really up to you. Might be a good
idea to
> check the strengths and weaknesses of hashes; I had a page, I'll
have to
> see if I can find again that explained the strengths for certain
hashes
> and etc.
>
> Thanks,
> Tyler Littlefield
> Web: tysdomain.com
> email: tyler@xxxxxxxxxxxxx
> My programs don't have bugs, they're called randomly added features.
>
> ----- Original Message -----
> From: "Mark Long" <markalong64@xxxxxxxxxxx>
> To: "Program-l" <program-l@xxxxxxxxxxxxx>
> Sent: Wednesday, March 25, 2009 2:43 AM
> Subject: [program-l] Re: Text file checksum code
>
>
>> If the file is of arbitrary length then it can be padded to have
the same
>> checksum. This is called a forced collision.
>>
>> If you hashed it using two algorithms then it would be very much
harder
>> to do. I suggest that a sha1 and an MD5 would defeat most
attackers.
>>
>> Sample code:
>>
>>
http://dotnetpulse.blogspot.com/2007/12/sha1-hash-calculation-in-c.htm
l
>> http://blog.brezovsky.net/en-text-2.html
>>
>> Hope that helps
>>
>> Mark
>>
>> --------------------------------------------------
>> From: "Jacob Kruger" <jacobk@xxxxxxxxxxxx>
>> Sent: Wednesday, March 25, 2009 7:53 AM
>> To: "Program-l" <program-l@xxxxxxxxxxxxx>
>> Subject: [program-l] Text file checksum code
>>
>>> Hi there
>>>
>>> Currently looking into implementing a form of custom licensing
system
>>> for some apps for work, and the one thing we might need to do is
to use
>>> some form of checksum to make sure that the text/XML file to be
used for
>>> storing licensing information hasn't been modified as such, so am
>>> currently looking for some sample code/examples related to doing
this
>>> with text files since it doesn't as such seem to be naturally
supported
>>> within the CLR framework/C#/VB.Net.
>>>
>>> Any ideas?
>>>
>>> Apart from that, here's a link to MS's own updated C# code samples
file
>>> download page:
>>>
http://code.msdn.microsoft.com/Release/ProjectReleases.aspx?ProjectNam
e=csharpsamples&ReleaseId=8
>>>
>>> Stay well
>>>
>>> Jacob Kruger
>>> Blind Biker
>>> Skype: BlindZA
>>> '...fate had broken his body, but not his spirit...'
>>>
>>> ** To leave the list, click on the immediately-following link:-
>>> ** [mailto:program-l-request@xxxxxxxxxxxxx?subject=unsubscribe]
>>> ** If this link doesn't work then send a message to:
>>> ** program-l-request@xxxxxxxxxxxxx
>>> ** and in the Subject line type
>>> ** unsubscribe
>>> ** For other list commands such as vacation mode, click on the
>>> ** immediately-following link:-
>>> ** [mailto:program-l-request@xxxxxxxxxxxxx?subject=faq]
>>> ** or send a message, to
>>> ** program-l-request@xxxxxxxxxxxxx with the Subject:- faq
>>>
>> ** To leave the list, click on the immediately-following link:-
>> ** [mailto:program-l-request@xxxxxxxxxxxxx?subject=unsubscribe]
>> ** If this link doesn't work then send a message to:
>> ** program-l-request@xxxxxxxxxxxxx
>> ** and in the Subject line type
>> ** unsubscribe
>> ** For other list commands such as vacation mode, click on the
>> ** immediately-following link:-
>> ** [mailto:program-l-request@xxxxxxxxxxxxx?subject=faq]
>> ** or send a message, to
>> ** program-l-request@xxxxxxxxxxxxx with the Subject:- faq
>
> ** To leave the list, click on the immediately-following link:-
> ** [mailto:program-l-request@xxxxxxxxxxxxx?subject=unsubscribe]
> ** If this link doesn't work then send a message to:
> ** program-l-request@xxxxxxxxxxxxx
> ** and in the Subject line type
> ** unsubscribe
> ** For other list commands such as vacation mode, click on the
> ** immediately-following link:-
> ** [mailto:program-l-request@xxxxxxxxxxxxx?subject=faq]
> ** or send a message, to
> ** program-l-request@xxxxxxxxxxxxx with the Subject:- faq
>
** To leave the list, click on the immediately-following link:-
** [mailto:program-l-request@xxxxxxxxxxxxx?subject=unsubscribe]
** If this link doesn't work then send a message to:
** program-l-request@xxxxxxxxxxxxx
** and in the Subject line type
** unsubscribe
** For other list commands such as vacation mode, click on the
** immediately-following link:-
** [mailto:program-l-request@xxxxxxxxxxxxx?subject=faq]
** or send a message, to
** program-l-request@xxxxxxxxxxxxx with the Subject:- faq
** To leave the list, click on the immediately-following link:-
** [mailto:program-l-request@xxxxxxxxxxxxx?subject=unsubscribe]
** If this link doesn't work then send a message to:
** program-l-request@xxxxxxxxxxxxx
** and in the Subject line type
** unsubscribe
** For other list commands such as vacation mode, click on the
** immediately-following link:-
** [mailto:program-l-request@xxxxxxxxxxxxx?subject=faq]
** or send a message, to
** program-l-request@xxxxxxxxxxxxx with the Subject:- faq
Other related posts:
