MDHashTool Help Page
Introduction
Copying and License Information
Checking Download File Integrity
Generating Digests for Files and Text
Preferences
Uninstalling MDHashTool
Introduction
Message Digest Hash Tool is a Firefox extension which can be used to
compute
Message
Digests for
files and/or text strings using various algorithms (currently MD5 and
SHA-1). These
digests, sometimes referred to as "digital fingerprints", are commonly
used to verify that
files have not been corrupted or tampered with. MDHashTool makes it
easier for Firefox
users to check the integrity of their downloads and generate digests
for files they want
to share.
Hash generation is based on the md5sum/sha1sum backend modules
ported from the
GNU Core Utilities
package with as little modification as possible. MD Hash Tool replaces
the command line
interface of those GNU utilities with a graphical user interface that
can be opened from
the browser Tools menu or the downloads window context menu.
Other features:
- Supports drag and drop for files and text selections
- Simplifies the process of comparing computed and reference
checksums - type or copy&paste (e.g. from download site) reference
checksum to perform comparison
Feel free to offer ideas and suggestions - your feedback is welcome.
Contact me directly at melodious@mindspring.com
or visit the MDHashTool homepage listed below. You may report
bugs via the MozDev Bugzilla system or by emailing me.
MDHashTool homepage:
http://mdhashtool.mozdev.org
Copying and License Information
MDHashTool - Message Digest (MD5, SHA-1, etc.) tool
Copyright (c) 2005 Charles Melhorn
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA
Or see the GNU web site at: http://www.gnu.org
Checking Download File Integrity
You will often find an MD5 or SHA1 digest value (typically represented
as a string of 32 hexadecimal values) supplied along with files you
download off of the internet. These digests, sometimes referred to as
"digital fingerprints", are commonly used to check files for corruption
or tampering. By comparing the reference digest value provided by the
file originator to the actual value computed for your copy of the file
and verifying that they match, you can be reasonably certain that the
file has not been altered. MDHashTool simplifies this process of
comparing computed and reference checksums for downloads by adding a
new item to the download manager context menu.
To check files downloaded using Firefox, open the download manager (Tools
-> Downloads
). Select the file of interest, right-click on
it, and choose "Check Digest" from the context menu:
This will compute a digest for the file and open the Check File Digest
dialog:
By default, MDHashTool will compute an MD5 digest when the window is
first opened (see Preferences to change
this behavior). You can copy the computed digest for your file to the
clipboard by right-clicking on the digest value and selecting "copy"
from the context menu. If you need to check the SHA1 digest for your
file, select "SHA1" from the Algorithm drop down box to compute and
display the proper digest.
To verify the file's integrity, you'll need to compare the computed
digest with the reference digest. Copy the reference digest value from
the website distributing the file, and paste (or type) it into the
Reference Digest textbox. If the values are equal, the match indicator
will turn green and display "match":
If the digest values are not equal, the match indicator will turn
red
and display the words "no match". Before you
conclude that the downloaded file is corrupt, be sure that you copied
the reference value correctly and are comparing the same type of digest
(MD5, SHA1, etc.). In addition, verify that the reference digest
supplied by the file originator is up to date.
Note that file digests provide no
assurance about the file author's identity (unlike files signed with a
public certificate) or intentions. They merely indicate with a
high degree of certainty that a file has not been altered from the
point when the reference digest was generated to the point when you
received it.
To check downloaded files that are not accessible from the download
manager (because they've been moved, renamed, removed from the
downloads list, or were downloaded with other programs), see the
following section Generating Digests for
Files and Text.
Generating
Digests for Files and Text
MDHashTool can be used to compute Message Digests for files
and/or text strings using various algorithms (currently MD5 and SHA-1).
These digests, sometimes referred to as "digital fingerprints", are
commonly used to verify that files have not been corrupted or tampered
with. To generate digests for files you wish to distribute or verify,
open the MDHashTool main window from the browser Tools menu (Tools
-> MD Hash Tool
).
The input type will be set to "file" by default. Select the desired
digest algorithm from the dropdown box, and click the "browse..."
button to open the file selection dialog. You'll need to specify the
file via this dialog - you cannot type directly in the filename
textbox. Once the file is selected, click the "compute digest" button.
The resulting digest value will be displayed in the Message Digest
field at the top of the window. To change the algorithm, select a new
type from the dropdown box and click "compute digest" again.
If you prefer, you can drag a file from your file manager or desktop
(on systems that support drag and drop) to the MDHashTool window. When
a file is dropped on the window, the input type will automatically be
set to file and the digest will be computed using the currently
selected algorithm.
You can copy the computed digest for your file to the clipboard by
right-clicking on the digest value and selecting "copy" from the
context menu. To generate digests for text strings, follow the
procedure described above, but set the input type to "text" and enter a
string in the textbox. You can also drag text selections from other
applications to the MDHashTool window. When the text is dropped, the
input type will automatically be set to "text" and the digest will be
computed using the currently selected algorithm.
To compare the computed digest against a reference value, open the
Compare Message Digests dialog by selecting "compare..." from the
digest value context menu.
Copy the reference digest value from the website distributing the file,
and paste (or type) it into the Reference Digest textbox. If the values
are equal, the match indicator will turn green and display "match":
If the digest values are not equal, the match indicator will turn
red
and display the words "no match". Before you conclude that the file is
corrupt, be sure that you copied the reference value
correctly and are comparing the same type of digest (MD5, SHA1, etc.).
In addition, verify that the reference digest supplied by the file
originator is up to date.
Preferences
You can bring up the preferences dialog by clicking the Options button
at
the bottom of the main MDHashTool window. Modify the settings as
desired, then
press the 'OK'
button to save the changes. If you don't wish to save your changes, use
the 'cancel'
button to close the preferences dialog.
The following preference options are available:
Preference
|
Default Value
|
Description
|
default hash algorithm
|
MD5
|
Determines the default value for
the hash algorithm drop down box in the main MDHashTool window and in
the download Check Digest dialog. The type of digest that is computed
when the download Check Digest dialog first opens is also controlled by
this value. |
MDHashTool preferences use the preference node
"extensions.mdht." and are stored in the "prefs.js" file (along with
the
other Firefox preferences) in the user's profile directory. On Windows
systems, this directory is usually Documents and
Settings\<user_name>\Application
Data\Mozilla\Profiles\<profile
name>\<random string>
or something similar. On Linux,
it
would be ~/.mozilla
.
Uninstalling
Use the FireFox extension manager to uninstall MD Hash Tool. Open the
extension
manager by choosing "Extensions" from the browser 'Tools' menu, select
the MDHashTool
listing, and click the uninstall button at the bottom of the window.
Restart the browser
to complete the removal.
Revised:
02/16/05
This document created and maintained with Mozilla Composer