Bug in CFX_HASH? 2 files, same hash.

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January 29th, 2005, 12:59 PM

WeBoat

Contributing User

Join Date: Jul 2004

Posts: 61

Time spent in forums: 10 h 5 m 43 sec
Reputation Power: 5

Bug in CFX_HASH? 2 files, same hash.

I've been playing with CFX_HASH today. Very strangely, two of the first files I've tried with it are returning the same hash.

1.jpg size: 62KB.
2.jpg size 14kb.

Here is what my test code is returning:

File 1: C:\\webs\\officex3\\hash\\1.jpg
File 2: C:\\webs\\officex3\\hash\\2.jpg
Hash Algorithm: SHA

Hash of File 1: 30567F6B52AF60449A6113D3C80FB9F850B7426A
Hash of File 2: 30567F6B52AF60449A6113D3C80FB9F850B7426A
These Files are Identical to one another

Here is the test code:





<CFSET #Path# = "C:\\webs\\officex3\\hash\\">

<CFSET #FileName1# = #Path# & "1.jpg">
<CFSET #FileName2# = #Path# & "2.jpg">

<CFPARAM Name="Cipher" Default="SHA">

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
<HTML>
<HEAD>
<TITLE>Using CFX_HASH in Document Verification Applications</TITLE>
</HEAD>

<BODY BGCOLOR=FFFFFF>

<CENTER>
<TABLE CELLPADDING=10 VALIGN="TOP">
<TR><TD COLSPAN=2>
This demonstration uses the CFX_HASH tag in conjunction with CFFILE to
calculate a digital "fingerprint" of a file. The technique used here makes use of the <CFFILE Action=READ Variable=MyVar> command in Cold Fusion. Here we read the contents of a file into a CF Variable, and
then process that variable in CFX_HASH. The resulting digest can then be compared to the message digests
generated against other copies of the file to verify that the files are identical.

Note that if you calculate the message digest of identical files, you should get the same results.
In this case, we are comparing the message digest of two identical files,
so the resulting digital fingerprints should be identical.


<CFOUTPUT>
<PRE>
File 1: <A HREF="#FileName1#">#FileName1#</A>
File 2: <A HREF="#FileName2#">#FileName2#</A>
Hash Algorithm: #Cipher#
</PRE>
</CFOUTPUT>


<CFFILE ACTION="READ"
FILE="#FileName1#"
VARIABLE="ContentsA">

<CFFILE ACTION="READ"
FILE="#FileName2#"
VARIABLE="ContentsB">


<CFX_HASH CIPHER=#Cipher# InputString=#ContentsA# VARIABLE="Hash1">
<CFX_HASH CIPHER=#Cipher# InputString=#ContentsB# VARIABLE="Hash2">


<CFIF #Hash1# eq #Hash2# >

<CFSET #MSG# = "These Files are Identical to one another" >
<CFELSE>
<CFSET #MSG# = "These Files are NOT Identical to one another" >
</CFIF>

<CFOUTPUT>
Hash of File 1: #Hash1#
 Hash of File 2: #Hash2#

#MSG#
</CFOUTPUT>


</TD>
</TR>
</TABLE>
</CENTER>

These two files return the same hash for SHA or MD5 hashes. Other files seem to work fine.

I am also going to attach the applicable files including a zip of CFX_HASH.DLL. Am I doing something wrong? I thought this was not possible.

Thanks

Tim

Attached Images

	1.jpg (61.8 KB, 139 views)
	2.jpg (13.2 KB, 197 views)

Attached Files

	validatefile.zip (1.2 KB, 255 views)
	CFX_HASH.zip (90.2 KB, 220 views)

January 29th, 2005, 01:06 PM

WeBoat

Contributing User

Join Date: Jul 2004

Posts: 61

Time spent in forums: 10 h 5 m 43 sec
Reputation Power: 5

I thought the following would fix it, but this just causes another problem:

It's in the CF_FILE statments.

Images have to be read in binary mode:


<CFFILE ACTION="READBINARY"
FILE="#FileName1#"
VARIABLE="ContentsA">

<CFFILE ACTION="READBINARY"
FILE="#FileName2#"
VARIABLE="ContentsB">

Now if I have two identical files, (I copied 1.jpg to 3.jpg and set that as my two files), it says they are NOT identical.

If a file is copied into different filenames, would it return a different hash?

This is very confusing.

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