calculated from a set of input data using a special algorithm. A checksum is most often used to verify the integrity of files. That is, in a rough approximation checksum is the key, which allows you to clearly distinguish two different data sets (two different files). For example, you downloaded a file from the Internet (games, installation), can you be sure that during the downloading process the file was not damaged and was completely downloaded? But using such a “faulty” file often leads to errors when installing a game or OS or anything. Moreover, you may not know that the error arose precisely because of a file damaged during the download process, blaming your computer for all the problems.
So, to avoid such problems, checksums are used. Often, many resources, along with a link to a file, also leave a checksum of this file. And after downloading this file, you will be able to compare the checksum of the downloaded file with the one that was left on the resource and definitely make sure that the file was downloaded without errors.
To calculate and compare checksums, use special programs. The most common of them is HashTab. This program is free. You can download it from here:
To install, unpack the archive and run the program installation file.
After installation, the program shortcut does not appear, this program is not in the menu quick launch Start. To use the program, click right click on any file and select Properties(we will do this operation with the downloaded archive). Please note that in the file properties window there appears new inset File hashes.
In order to compare the checksums of files, copy the hash sum from the program website and paste it into the field Hash comparison properties windows.
Hash is individual unique code, which corresponds to a specific unit of information, a mathematically calculated image of a specific file. When a file undergoes any modification, the hash sum of this file changes accordingly.
After downloading files from the Internet, especially ISO disk images of various products, it is a good idea to compare the hash sum of these files with the one published by the manufacturer of these products, in order to determine whether the files have been modified in any way (by introducing third party programs, viruses, etc.).
In most cases, information about the hash sums of a file is provided by the developer to the user on the website after describing its characteristics or system requirements.
By checking the hash code, the file is protected from modification. Its verification is especially relevant when downloading operating system disk images not from the manufacturer’s website, but from so-called file exchangers and torrent trackers.
If a checksum mismatch is detected, it is better to think 100 times before using the disk in this way. You may ask, how can you find out the checksum of a file in the Windows operating system?
HASH SUM
I’ll answer, there is such a small and at the same time free program called HashTab, which is integrated into Windows Explorer and will help you easily determine the hash sum (checksum) of the file you downloaded in order to verify its authenticity and integrity. The program can be downloaded from the official website at:
Http://implbits.com/products/hashtab/HashTab_v6.0.0.34_Setup.exe
where after going to the site you need to click on the “Download Now!” button.
In the field that appears, enter your address Email, to which you will receive a letter with a link to download the program, and click the “Send Download Link” button.
We check the mail and see a letter that provides the URL where we can download the program, the size of the program and its checksum.
Download the program, specifying the folder.
Extract the program installer from the archive and launch it by double-clicking the left mouse button. In the installer window that opens, click on the “Next” button.
In the next window, we agree to the license by clicking on the “I Agree” button.
Select the folder to install the program (it’s better to leave it as default) and click the “Install” button.
We complete the installation by clicking the “Finish” button.
CHECK SUM
Upon completion of installation, the program is integrated into context menu Conductor operating system. To display the checksum of a file, we need to right-click on it and click on “Properties”.
In the window that opens, click on the “File hash sums” tab.
For large files Sometimes you need to wait a few seconds for the hash calculation to progress.
Upon completion of the calculation, in the “Hash Value” window we will see the checksum for the file.
In the “Settings” of the program, you can add additional hash sums to be displayed and configure it in more detail (I leave it at default).
In order to compare the checksum of a disk image (in my case), I go to the official website and look for where the hash sum of the image is indicated (on the site I find the posted file “MD5SUMS”).
I open this file and look for the checksum for my disk image (this is ubuntu-12.10-desktop-i386.iso).
I copy it from the site.
I paste it into the “Hash Comparison” field in the “File Hash Sum” tab of my disk image and see a green checkmark indicating that the checksum of the file completely matches the checksum of the disk image on the official website.
You can check the hash sum of 2 files in another way by clicking on the “Compare file” button, selecting the file we need in Explorer and clicking on the “Open” button, and look at the result.
In this way we try to protect ourselves from using modified versions of files.
So, you've worked long and hard to download a Windows image, and now you want to make sure that not a byte is lost along the way. Or the distribution package was brought to you by the good fairy, and you want to check if it is connected with pirates. To determine the integrity of the distribution, you will need two things - a checksum and a program to check it.
Windows image checksums
Upd. 2017. Microsoft has moved downloads from MSDN to a new site, https://my.visualstudio.com/downloads, where a subscription is required to access the images. Therefore, without subscribing using the method below, it is no longer possible to find out the checksum.
Microsoft publishes their product checksums on MSDN, specifying SHA1 as the hash type. Search for the language version and edition of your Windows and click Intelligence to see the checksum below.
That's half the battle.
Checksum verification using the built-in certutil utility
If you do not specify the parameter -sha1, the utility will calculate the MD5 hash.
As you can see, everything is very simple! You can use this method to verify the MD5 or SHA1 checksums of any files.
Checksum verification using HashTab program
If command line scares you, you can check the checksum in a simpler way.
- Download and install the HashTab program.
- Right-click on the image file and select Properties.
- Go to the "File Hashes" tab.
Each file has its own unique value that can be used to validate the file. This value is called a hash or checksum. It is often used by developers software when accessing files. The file is verified using the checksum to determine its integrity and matches the specified identifier.
There are several algorithms for calculating the checksum of a file, among which the most famous and common are MD5, SHA256, SHA1, SHA384. Calculate file hash, that is, its checksum, can be done using both standard Windows tools and third-party services. In this article we will look at how to do this.
Table of contents:How to find out the hash of a file via the command line
The Windows command line allows you to run various actions, both with the system itself and with individual files. Through it, you can determine the checksum of files using the built-in CertUtil utility.
To find out the hash of a file via the command line, just enter the following query into the command line:
Certutil -hashfile *path to file* *algorithm*
Instead of *path to file* you need to enter the full path to the file. For example: d:\8.jpg
Instead of *algorithm* you need to enter the name of the algorithm by which you want to calculate the checksum. The CertUtil utility can calculate a checksum using the following algorithms: MD2, MD4, MD5, SHA1, SHA256, SHA384, SHA512.
By executing the specified command, you will be able to see the file hash calculated using the CertUtil utility.
How to find out the hash of a file using the PowerShell utility
Another one built into Windows utility, which is capable of determining the checksum of a file is PowerShell. It differs from CertUtil by supporting a larger number of algorithms for calculating the checksum: SHA256, MD5, SHA384, SHA1, SHA512, MACTripleDES, RIPEMD160.
To check the hash through the PowerShell utility, use the following command:
Get-FileHash *path to file* | Format-List
Instead of *path to file* you must specify the full path to the file whose checksum is being checked.
It is important to note that by default the PowerShell utility calculates the checksum using the SHA256 algorithm.
If you want to use a different algorithm, you must specify this in the command when executing the request. For example, to determine a hash using the MD5 algorithm, you will need to run the command:
Get-FileHash *path to file* -Algorithm MD5 | Format-List
Instead of MD5, you can specify other algorithms supported by the utility.
How to find out the hash of a file using the HashTab utility
Besides Windows tools to determine the checksum of a file you can use third party applications. For example, one of convenient programs capable of determining the hash of a file is HashTab. This is an extremely simple application that can be downloaded for free from the Internet.
After downloading HashTab programs and installation, a new tab is created in the file properties, which is called “File hash sums”. In this tab you can see the checksum calculation for a file in various algorithms.
So, you've spent a lot of time downloading the Windows 7 image, and now you want to make sure that not a byte is lost along the way. Or the distribution package was brought to you by the good fairy, and you want to check if it is connected with pirates. To determine the integrity of the distribution, you will need two things - a checksum and a program to check it.
Windows 7 image checksums
Microsoft publishes their product checksums on MSDN or TechNet, specifying SHA1 as the hash type. Find the language version and edition of your Windows 7 and click Intelligence to see the checksum.
That's half the battle.
Checksum verification using the File Checksum Integrity Verifier utility
Microsoft, of course, has its own command line utility for calculating and verifying file checksums - File Checksum Integrity Verifier(fciv.exe). It can be downloaded from KB841290 (where the syntax is also described in detail), or via a direct link (41 kb). Next, I assume that you know where the utility is unpacked and where it is saved Windows ISO image 7.
It is enough to execute one command in the command line (Start - Search - cmd):
<путь к утилите>\fciv.exe -sha1<путь к ISO>\filename.iso
For example, if the utility is on the desktop and the ISO image is in the root of drive D, the command will look like this:
%userprofile%\desktop\fciv.exe -sha1 D:\en_windows_7_ultimate_x86_dvd_x15-65921.iso
And the result is the checksum of the file:
If you do not specify the parameter -sha1, the utility will calculate the MD5 hash.
As you can see, everything is very simple! You can use this method to verify the MD5 or SHA1 checksums of any files.
Checksum verification using HashTab program
If the command line scares you, there is an easier way to check the checksum.
- Download and install the program.
- Right-click on the image file and select Properties.
- Go to the "File Hashes" tab.
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