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Md5 Checksum

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Категория: Windows: другое

Описание

MD5 Checksum Verifier v5

RSLOAD.NET - скачай все бесплатно

Захотелось опубликовать простенькую программу, цель которая проверять контрольную сумму любого выбранного файла, базируется она на алгоритме MD5, я думаю из названия это понятно всем. Если рассматривать интерфейс, то он конечно не очень красочен, невзрачен, слишком простоват, но суть конечно не в этом, а в том насколько хорошо программа справляется с поставленной целью, а делает она это довольно неплохо, хотя конечно на нашем проекте есть бесплатные аналоги, которые могут гораздо больше, но это дело вкуса, в любом случае вы всегда можете скачать MD5 с нашего сайта по ссылке в полной новости.

После запуска и регистрации утилиты, вы сможете выполнять всего две операции, генерировать контрольную сумму с целью потом разместить ее на каком-то сайте чтобы пользователи имели ввиду и могли потом сравнивать ее с полученной, либо вы можете просто проверять контрольную сумму MD5, думаю разобраться в интерфейсе что куда нажимать вы сможете без особых проблем.

Цитата: sure

Вот зациклились вы на одной папке…, попробую объяснить на пальцах :), если по-другому ни как.

Не стоило. У меня достаточно собственного воображения, чтобы представить, что значит кнопка "Сравнить файл. " на скрине tigrr. "Зациклились" - грубо, и не обоснованно.

Нафига мне поиск нужен.

Не разобравшись. - это не ТОТ поиск, который ищет файлы. Это к вашему примеру вообще не при делах. И я его просто упомянул к слову, нужды в таком поиске у меня ещё не возникало.

Обычно я новое сравниваю со старым в ТС, оптом, - целиком две папки с подпапками (синхронизация). Видно и что новое, и что то же самое, и в вычислениях хешей нет необходимости - и так всё очевидно. Сразу можно и содержимое сравнить в изменившихся файлах (если это интересно или нужно). И все .ini заодно можно перенести.

(Плюс и сами .md5 TC и создаёт и проверяет не хуже HashCheck - всего выбранного, и файлов и папок.)

"Свойства > Хеш-суммы файлов > Сравнить файл > Указываем путь ." - "доли секунды"??(!) - пускай:)

Но *указать путь* - это будет ровно столько же. сколько открыть этот путь во второй панели ТС. Хотя для одного единственного файла (в вашем примере) может действительно проще (немного) воспользоваться Hash Tab. Так же как это и немного проще, чем запомнив пару цифр, этот же путь пройти не в окне выбора файла для сравнения, а в Проводнике - и глянуть хеш второго файла там.

И вполне естественно, что ради этого "немного" я не буду устанавливать ещё и Hash Tab.

sure. обсуждение это было не ради ВАС персонально. Я знаю точно. что одному человеку эта *мини-рекламная-компания* помогла.

И никто никому ничего не навязывает, и никого не переубеждает - написал же :

ДЕЛО ПРИВЫЧКИ. и субъективных немотивированных пристрастий

троллям: Мёртвого льва может лягнуть даже осёл.

Другие статьи, обзоры программ, новости

MD5 & SHA Checksum Utility Download

Generate and verify a MD5, SHA-1 & SHA-256 hash from a file

MD5 & SHA Checksum Utility is a tool that allows you to verify the integrity of a file by finding out its MD5, SHA-1, SHA-256 and SHA-512 signatures, as the name implies. Its features can be seamlessly handled by inexperienced users.

This is a portable application, so installing MD5 & SHA Checksum Utility is not necessary. It means that you can store the app on a USB flash drive or similar storage unit, in order to run it on any computer.

Otherwise, you can simply drop the executable file anywhere on the hard drive and run it. What's worth mentioning is that no leftover items can be found in the Windows Registry or on the hard drive after deleting the tool. Also, you can carry MD5 & SHA Checksum Utility in your pocket wherever you go.

The interface of the program is quite simple to figure out, as all the options are visible in the main window. So, you can open a file by using either the file browser or "drag and drop" method; the MD5, SHA-1, SHA-256 and SHA-512 checksums are automatically displayed and you can copy either of them or all text to the Clipboard. In addition, you can insert another hash, in order to compare it to the file's.

The lightweight program is not a concern to the computer's overall performance, as it requires a very small amount of CPU and system memory. It has a good response time and instantly calculates the hashes. We have not encountered any issues during our testing; the tool did not freeze, crash or pop up error dialogs. Thanks to its intuitive layout and overall simplicity, novices can seamlessly work with MD5 & SHA Checksum Utility.

CURRENT VERSION: 2.1 FILE SIZE: 82 KB DEVELOPER: Raymond Lin RUNS ON: Windows XP / Vista / 7 / 7 64 bit / 8 / 8 64 bit CATEGORY: C: \ Security \ Security Related

MD5 - SHA Checksum Utility - Free download and software reviews - CNET

Quick Specs Editors' Review

Cryptographic hash functions are commonly used to guard against malicious changes to protected data in a wide variety of software, Internet, and security applications, including digital signatures and other forms of authentication. Two of the most common cryptographic hash functions are the Secure Hash Algorithm (SHA) and Message Digest Algorithm-5 (MD5). Checksum utilities are used to verify the integrity of generated hashes. There are two basic types, those that calculate checksum values and those that also validate them by checking them against a list of values for the protected data, which is the only way it can be done. Raymond Lin's MD5 & SHA-1 Checksum Utility is a standalone freeware tool that generates and verifies cryptographic hashes in MD5 and SHA-1.

The program has a basic, utterly functional interface that should pose no trouble for anyone with the knowledge and skill to actually need it. To generate or verify a hash, you simply browse to the file of choice, select either MD5 or SHA-1, and click either Copy to generate the hash or Verify to check its integrity. A Paste function automatically enters the generated hash for verification at the click of a button.

MD5 & SHA-1 Checksum Utility is free to download and use, though Ray accepts donations from satisfied users. At a mere 57k, his checksum tool is about as small as a useful, functioning utility can be in this age of bloatware, and even more so considering that it's certified to work in Windows Vista and 7.

HowToMD5SUM - Community Help Wiki

Introduction

When one has downloaded an ISO file for installing or trying Ubuntu, it is recommended to test that the file is correct and safe to use. The MD5 calculation gives a checksum (called a hash value), which must equal the MD5 value of a correct ISO.

The program md5sum is designed to verify data integrity using the MD5 (Message-Digest algorithm 5) 128-bit cryptographic hash. MD5 hashes used properly can confirm both file integrity and authenticity.

In terms of integrity, an MD5 hash comparison detects changes in files that would cause errors. The possibility of changes (errors) is proportional to the size of the file; the possibility of errors increase as the file becomes larger. It is a very good idea to run an MD5 hash comparison check when you have a file like an operating system install CD that has to be 100% correct.

In terms of security, cryptographic hashes such as MD5 allow for authentication of data obtained from insecure mirrors. The MD5 hash must be signed or come from a secure source (an HTTPS page) of an organization you trust. See the MD5SUMS file for the release you're using under http://releases.ubuntu.com (and optionally the PGP signatures in the MD5SUMS.gpg file), or refer to the secure UbuntuHashes page for the official list of Ubuntu MD5 hashes.

While security flaws in the MD5 algorithm have been uncovered, MD5 hashes are still useful when you trust the organization that produces them. Moving to more secure hashes like SHA-256 and Whirlpool is under discussion.

The official page containing MD5 hashes for Ubuntu, Kubuntu, Edubuntu Xubuntu and Lubuntu is UbuntuHashes. More recent hashes may be available at http://releases.ubuntu.com/. choose the relevant distribution and click on the MD5SUMS file.

MD5SUM on Linux

Most Linux distributions come with the md5sum utility so installation is usually unnecessary.

Check the iso file Manual method First open a terminal and go to the correct directory to check a downloaded iso file:

Linux is case sensitive so "Downloads" is NOT "downloads" . Then run the following command from within the download directory.

md5sum should then print out a single line after calculating the hash:

Compare the hash (the alphanumeric string on left) that your machine calculated with the corresponding hash on the UbuntuHashes page.

An easy way to do this is to open the UbuntuHashes page in your browser, then copy the hash your machine calculated from the terminal into the "Find" box in your browser (in Firefox you can open the "Find" box by pressing <Ctrl> <F>).

When both hashes match exactly then the downloaded file is almost certainly intact. If the hashes do not match, then there was a problem with either the download or a problem with the server. You should download the file again from either the same mirror, or from a different mirror if you suspect a server error. If you continuously receive an erroneous file from a server, please be kind and notify the webmaster of that mirror so they can investigate the issue.

Semi-automatic method

Ubuntu distributes the MD5 hashes in a file called MD5SUMS near the bottom of the download page for your release http://releases.ubuntu.com.

First download the MD5SUMS file to the same directory as the iso. Then run the following in a terminal.
md5sum will generate a bunch of warnings. Don't worry: the OK message will be buried somewhere within it!
In this case the message we want is on the seventh line.

Once you have verified the md5 hash, go ahead and burn the CD. You may want to refer to the BurningIsoHowto page.

Check the CD

So far so good, you have downloaded an iso and verified its integrity. When you boot from the CD you will be given the option to test its integrity. Great, but if the CD is corrupt then you have already wasted time rebooting. You can check the integrity of the CD without rebooting as follows.

Checking the CD directly

You would think you could simply use a command like this to get the MD5 hash of a burned image:

However this will almost NEVER be the same hash as the iso image that was burned to the disk, because this command includes the empty space at the end of the disk, which changes the hash. So you must check only the part of the disk that was on the iso.

Manual method

First we need to know the size of the iso image. You could open up your favorite graphical file manager such as Nautilus or Dolphin, but since you need to use the command line anyways, you might as well use ls.

Now that we know the size of our iso image is 732766208, we can use dd to pipe only 732766208 bytes from our cdrom device into md5sum. Use a block size of 1 and set count to the size of the iso image. Note that this will probably take several minutes, so grab a snack and come back in a while.

You could probably speed this up by using a larger block size (bs) and dividing count by the new block size. Since all iso images are multiples of 2048, that is an appropriate block size.

Check the calculated hash (in this case 24ea1163ea6c9f5dae77de8c49ee7c03) against UbuntuHashes as shown for the iso file above. Depending on your system, you may need to change cdrom to cdrom0 (or even cdrom1 if you have two CD drives).

Automated Script

Here is a shell script that will check the md5 hash of a burned disk and compare it to the hash of an iso image. Copy and paste it into your favorite text editor and save it as eg. hashcdrom.sh.

Now open a terminal and type

Note that if your cdrom device is /dev/cdrom, you can omit that parameter.

It should print out something like

If you verified that the iso image is okay (above), than you need not check the hash against UbuntuHashes.

This script has some nifty features. For example, if md5deep is installed (sudo aptitude install md5deep ), it will use it to print out some progress information, such as how many bytes copied. You can also make it use different hashing algorithms such as sha256 and whirlpool by setting the CHECKSUM environment variable to the command you want to use to create the hash:

This shell script depends on certain features found only in GNU grep, so it probably will not work on systems that do not ship the GNU utilities.

A method using wodim instead of dd

where 352113 is result of dividing size of iso file in bytes by 2048.

Check the files on the CD The MD5 hashes for every file on the CD are listed in a file called md5sum.txt . You can use this file to check the integrity of all the files on the CD.

This will automatically check every file against the MD5 hashes stored in the file and outputs any failures. (Again, you may need to change cdrom . depending on your system). Beware, it can take a long time so don't worry if your terminal seems to have hung; provided the CD drive is still accessing, it is probably still working. It should not output anything if it there were no errors, and an error message if a file failed the check. The grep command option -v "OK$" filters out all of the files that pass the check, because there are usually a lot of them.

Congratulations, you now have a verified Ubuntu CD. Go ahead and use it (or play frisbee with it if you want).

MD5SUM on Mac OS X

There are three methods of using md5sum on an OS X machine.

Method 1 - The easiest (if MD5 is available) is using the Disk Utility program (Applications > Utilities, or by choosing "Utilities" from the Finder's "Go" menu). Open Disk Utility and wait for it to gather information about your disks. Go to the directory where you downloaded the Ubuntu disk image, and drag it to Disk Utility's dock icon (displays on the left-hand side of Disk Utility, underneath your physical drives). Select the iso file. Go to the "Images" menu and select Checksum > MD5. Be sure to choose "MD5" and NOT "MD5 image checksum" or "CRC-32 image checksum", as they are not the same and will give you different results.

Method 2 - If MD5 is not available in the Images > Checksum menu, open a terminal window (Applications > Utilities > Terminal.app). Type "md5", type a space, drag the iso file into the terminal window (appends command with iso file path), and press Enter. The command line returns the hash number.

Method 3 - You can use the Terminal.app and follow the instructions for MD5SUM on Linux. except use the command "openssl md5" instead of "md5sum".

Each method returns a hash number. Compare the hash number with the corresponding hash on the UbuntuHashes page. When both hashes match exactly, then the downloaded file is almost certainly intact.

If the hashes do not match, then there was a problem with either the download or a problem with the server. You should download the file again from either the same mirror, or from a different mirror if you suspect a server error. If you continuously receive an erroneous file from a server, please notify the webmaster of that mirror so they can investigate the issue.

digest(1) on Solaris Use the Solaris digest(1) command, specifying the md5 algorithm with the -a flag. For instance:
MD5SUM on Windows

Windows does not come with md5sum . You must download one from another location, preferably one that you trust. There are command line utilities (md5sum.exe ) that work similarly to the Unix utility; one public domain version with source is available from Fourmilab. but the version available from Cygwin is probably easier to install and update, and Cygwin is also recommended and trusted as the source for many more Unixy utilities. Once installed, Cygwin's md5sum behaves exactly as described in MD5SUM on Linux above.

There are also graphical tools such as the one used in the walk-through provided below.
Download and install winMD5Sum. a free and open source hash verification program.
  • Right-click the ISO file.
  • Click Send To, then winMD5Sum .
  • Wait for winMD5Sum to load and finish the checksum (this may take a significant amount of time depending on your computer's performance).
  • Copy the corresponding hash from UbuntuHashes into the bottom text box.
  • Click "Compare"
  • A message box will say "MD5 Check Sums are the same" if the hashes are equal.
  • MD5SUM with "Checksums calculator" "Checksums calculator” is a free file checksum calculation utility, it can support the most commonly used file checksum algorithm, such as md5, crc32, and sha1, can batch process multiple files. This verification software has some useful features, but it is easy to understand and very easy to use. You can download the application here.

    The program while is running under Windows 7 64bit.

    MD5SUM on CD

    To see if your Ubuntu CD was corrupted when burned to the disk, see the CDIntegrityCheck page, or follow the instructions below.

    First mount the CD, if not already mounted:
    Then use the supplied md5sum file on the CD:

    Be patient, it takes some time. If the command outputs any errors, you'll know that either the burn was bad or the .iso is corrupt. Please note that this method does not verify authenticity unless the hash of the iso file is compared to the hash at the secure UbuntuHashes page.

    Finally, you can unmount the CD after leaving the folder:

    GT Explains: What is MD5 Checksum and How to Verify it

    GT Explains: What is MD5 Checksum and How to Verify it

    Ads by Google

    I still cry over the day I bricked my brand new Samsung Galaxy S while installing a custom ROM on it. I had to wait couple of weeks to get it fixed. It wasn’t a noob installing a custom ROM. I knew all about it (am a writer for GT you know). But I was careless and that’s what caused the problem.

    Talking about my carelessness, I downloaded the update file from a file hosting service as a free user using the default browser. I was so excited about flashing the new ROM that I didn’t realize that the download was interrupted in between which caused a failed installation resulting into a bricked ROM.

    For the rest of the time, while my phone was in the service center, I kept cursing myself for not checking MD5 checksum of the file before installing.

    If you are wondering what’s MD5 checksum and how it could have helped me, read on.

    Explaining MD5 Checksum

    MD5 checksum, the short for Message-Digest is an algorithm used in data security and cryptography fields. Don’t worry, instead of talking about all those cryptic tops we’ll straightaway jump to the point.

    If I were to explain you in simple words, you can think of MD5 as an alphanumeric string which is associated with every single file. Just like no two human beings can have identical fingerprints, in the same way, no two different files (local or on the network or on the World Wide Web) can have the same MD5 checksum.

    Now, just like by matching the fingerprint we can confirm the identity of an individual, we can confirm the authenticity of an individual file by matching the MD5 checksum. The best part is that you don’t need a forensic degree to do so.

    So let’s see how we can find the MD5 checksum for a given file.

    Checking the MD5 Checksum

    When you download critical files from the Internet – say an operating system or a new firmware for your smartphone – most of the websites supply the MD5 checksum in the download details to help you cross-check the file’s identity before proceeding to the installation.

    We will use a simple freeware called the MD5 Check (Softpedia Link) to check the file. The tool is portable so you can extract and run the executable file after your download. The tool’s interface is self-explanatory. There’s a browse button to browse for the file you want to know the MD5 for. A calculate button to calculate the checksum of the particular file, and finally two text boxes, in one of which the generated checksum will be produced and in the other you can paste the checksum of the same file from a legit source and check.

    That’s all, if both the checksums match, you are good to go.

    My Verdict

    Prevention is always better than cure and in the case of MD5 checksum verification, it hardly takes seconds. So don’t regret later like I did after a corrupt file caused all kinds of problems for me. Check the MD5 Checksum to verify the downloads (whenever you can locate the original MD5 Checksum that is).

    Image Credits: Jack Spades

    Free MD5 Checksum or Hashing Utilities (Free MD5sum Software) ()

    Free MD5 Checksum or Hashing Software

    The free MD5 software listed on this page will display a 128-bit hash of a file using the MD5 algorithm. It is primarily used to verify the integrity of files. For example, some download sites list the MD5 checksum of a file so that after you download the file, you can run one of the tools listed below on the file and find the checksum of the file you received. If the checksum does not match that published on the website, you can be sure that your download had been corrupted somewhere in transit.

    Note that MD5 is an insecure hash function - you should not use it as a security measure. Use it only as a rough gauge to check things like unintentional file corruption either from downloading, or a failing disk media or something like that. The reason it should not be used as a security measure is that it is possible for two different files to have the same MD5 checksum. But since it is unlikely that a file that is accidentally corrupted share the same MD5 checksum as the original, it is a useful tool for a casual check of file integrity.

    For the curious, MD5 is short for Message-Digest Algorithm 5.

    Related Pages Free MD5sum Message Digest Hash Tools

    WinMD5Sum is a small Windows utility that you can use from the Windows Explorer SendTo menu to check the integrity of a file using the MD5 checksum. Simply right click the file you wish to check, click the "Send To" menu, and select the WinMD5Sum program. The program will automatically launch and display the MD5 checksum. It has an added convenience facility where you can simply cut and paste the MD5 sum published elsewhere into one of its fields, and it will compare it with the MD5 checksum it generated. You do not need to manually check (character by character) to see if the MD5 matches with the actual published version.

    This is a Windows program to compute the MD5 hash value for a file. It supports drag and drop to its window, and also has an interface whereby you can paste the MD5 hash from somewhere else (eg your web browser) and have it compare with the MD5 it generates from a file.

    MD5Deep (Windows, Linux, FreeBSD, OpenBSD, NetBSD, Mac OS X, OpenSolaris, HP/UX)

    MD5Deep is a cross-platform set of programs that computes the MD5, SHA-1, SHA-256, Tiger or Whirlpool message digests (hash values) of one or more files. It can recursively check all the files in a directory (and its descendants), check files against a list of known hashes, etc. This is a command line program. Although the source code can be compiled for Windows, Linux. FreeBSD, OpenBSD, NetBSD. Mac OS X, OpenSolaris and HP/UX, only the Windows executables are available. The program is a work of the US government, and is thus not copy protected.

    FileCheckMD5 is primarily designed for you to quickly verify the integrity of your files that you keep as a backup. For example, if you save your files on a CD, and a year or so down the road want to check to make sure that the deterioration of the CD has not corrupted your files, this is the tool for you. The program scans all the files in a folder, saves the MD5 checksums of each file. At a future time, you can use the program again to scan the files and compare the checksums against what it had saved earlier.

    MD5Summer is a Windows MD5 sum generator. Source code is available.

    MD5sums is a command line program for Windows that runs in the Windows console. It generates MD5 message digests for one or more files. You can add it to the Windows SendTo menu so that it works from Explorer if you wish.

    DigestIT allows you to right click a file name and have the program calculate its MD5 or SHA-1 hash. You can also have it verify a file against an existing message digest string (hash value) automatically.

    FSUM is a command line file integrity checker that allows you to check the integrity of a file using one of 13 hash algorithms. Supported message digest checksums include MD2, MD4, MD5, SHA-1, SHA-2( 256, 384, 512), RIPEMD-160, PANAMA, TIGER, ADLER32, CRC32 and the custom hash algorithm used in eDonkey and eMule applications. It can act recursively in a directory. It supports the .MD5 and .SFV file formats for obtaining checksums. This is a Windows program.

    FCIV is a command prompt utility that computes and verifies the cryptographic hash values of files using the MD5 or SHA-1 algorithms. The above link goes to its documentation and has a link to the download page.

    GnuWin32 is a source of GNU utilities compiled for Windows. The Core Utilities contain numerous command line tools, including the GNU version of md5sum. If you use a different operating system. see the GNU Core Utilities entry on this page instead.

    The GNU core utilities also contain an md5sum checksum utility. You will have to download the source code and compile them yourself. Note that if you're running a system like Linux. you probably already have it installed. Like all GNU software, it is probably portable to POSIX-based systems like Linux and the BSDs. If you run Windows, see the GnuWin32 entry on this page instead.

    This is a command line MD5 checksum tool for Windows and Unix systems. A pre-compiled binary is available for Windows.

    HashTab adds another tab to a file's property sheet (invoked when you right-click a file in Explorer and select "Properties") that displays the MD5, SHA1, CRC-32, SHA-512, Tiger, Whirlpool, RIPEMD-128 hashes of the file. The hashes are not created until you click the "File Hash" tab. You can also customize which hashes it actually calculates, to save time. The program works under both the 32 bit and 64 bit versions of Windows. The program is only free for personal use, and you have to furnish an email address to them to get the download link.

    File Verification using MD5 Checksums on

    (or File Verification using MD5 Checksums)

    Anytime you move a data file (image or otherwise) there is a chance it can be corrupted, with the result that you might not end up with the same file with which you started. This can happen due to a variety of reasons including failing or faulty storage media, download or upload transmission errors, write errors during local copying or moving, as well as bugs in computer software.

    There are a couple of file transfer utilities, or synchronization applications that may use some form of checksum or other operation to verify file transfers. Utilities such as Chronosync or Synchronize! Pro X (Mac); as well as SyncBack Pro, or Acronis (Windows) can be used to verify file transfers, or to synchronize the files and folders between two different computers. However these are only good for verification so long as the files and folders for both sets stay in the same location. If you move a set of files or folders from a working drive to an "Archive" server because you want to get the files off the working drive, then all a verified transfer can do is let you know that the files matched at that point in time. That is certainly useful, but once you remove the files from the working drive, there is no way to tell if the files on the archive have developed a problem or have been changed without opening them each to test.

    Or can you?

    The Checksum results (or hashes) created using the tools mentioned below can be stored with the file for future reference; or used for other purposes such as discovering exact duplicates within an image collection. This flexibility is part of their utilitarian beauty; but the best thing is peace of mind. If that sounds intriguing, then read on to learn how you can create MD5 Checksums using free utilities on the Mac OSX or Windows platforms to verify file transfers and much more.

    Tribbles and Transporters

    Let's start with an analogy as this may help understand what we are trying to do. Pretend that each digital file you want to transfer is a tribble --you know, those cute furry animals from Star Trek that all look alike -- and the "checksum" (such as an MD5 checksum) is a DNA test to identify each tribble at the genetic level.

    A Maya rendering of a tribble, created by Clh288

    Lets say you want to use the Star Trek teleporter to move a bunch of tribbles from point A to point B (not necessarily a Klingon ship, but that is always an option). To your eyes, and mine, all tribbles look alike and you can't easily put a collar on them. So before you scatter their molecules across space, you first run a DNA test for each. Then after they arrive at point B, you round each of them up, and run the same test again. From comparing the results of the first test with the second you can verify that each of the tribbles is the same as the one you started with. However, as this "verification," is quite simple, all you learn is if the current test results match the previous, or if they failed.

    Of course you might also find that you have ten test results from the first test, and only nine tribbles when you get to point b. If so, you know that you are missing one (and even which one). If that is the case, then that probably means it's time to check the storage compartments or the engine room.

    Checksums are like DNA tests for your Files

    Think of creating a checksum like running a DNA test for your digital files. It gives you a way to easily check the integrity of each file, or even a folder full of files. Plus, at any time in the future that you suspect something has happened to a file, folder or drive, you can repeat the test by comparing the current test with the one that was originally done. If they match. Great. If they don't, then you know that you need to dig deeper. If you find that files are missing, then you can start searching for where they might have been accidentally moved (or deleted).

    Your alternative is to inspect each file periodically and make sure your software can open them. This serves as a check that they have not been corrupted, or that the media is not failing. It's also possible to keep a spreadsheet of the files in a given folder, or create an image catalog for each set of images in order to make sure everything is intact. By periodically checking you could find if a file was missing, but both of these methods will take more of your time, and/or require some level of visual inspection, meaning you are less likely to perform them on a regular basis.

    If you are maintaining files in two locations that you want to keep synchronized, then you might want to take a look at some of the applications and utilities mentioned earlier; or check out something called Rsync.

    Checksum Overview

    A checksum comparison is based on the simple premise that it is unlikely that an accidentally damaged file will produce the same checksum as the original file. Going back to the Star Trek Tribble analogy, if one of the furry creatures was damaged by the transporter, then it's unlikely that it's DNA signature would be the same after a problematic transport. If we do a "DNA" check before and after each transfer, then we can spot any problems right away, before they become bigger problems.

    A "cryptographic" hash uses a special procedure that takes an arbitrary block of data and returns a fixed-size bit string. You may not understand that bit of geekspeak, however, it's not any more important to know how this works than knowing about how gel electrophoresis works to understand DNA markers. What you do need to know, is that in this instance, an MD5 checksum (which is a form of cyptographic hash) created for each image can be stored as a 32 character "string" and the value is unlikely to repeat (it is not, however, impossible). For an in-depth explanation of how an MD5 hash is computed, Makeuseof has a nice one. If you want to see another way in which this works, play around with this online MD5 Hash Generator.

    Due to the way in which they are created, any change (accidental or intentional) to an image file will—in nearly all instances—change the hash value that is created. For example, change the metadata for an image, or retouch a blemish in the pixels, and when you resave the file and create a new hash/checksum; it should not match the hash for the original file. It is possible, in some instances that an image may have the same hash value generated, even though changes have occurred, but this would be rare.

    Likewise, if there was a hard drive error, or a problem when a file was restored, these changes to the file should change it enough that the hash value will be different, and thus will be noted as failures in your report. You should see these flagged as "bad" (instead of OK) or some other type of "fail" notices in your report or some type of feedback in the utility. [note, I've received a few emails from others noting that there are some methods that can be used to modify a document (typically text files) and then resave it in such a way that the hash will match the earlier version. This could be used by those wishing make changes which will escape detection on a storage system. However, in this example—where you are creating the hash for a file or folder, then moving the file or folder, and then comparing the hash values—it's unlikely that this type of tampering would come into play].

    An ideal "checksum" process should meet the following three tests.

    It should be easy to compute for any given data file (of which image files are one)

    Each check/sum hash should be unique (they are unlikely to match other hashes for similar images)

    It is not possible to modify a data file without changing its hash

    Getting Started

    While I know and can use"command line" interfaces, I don't find them that easy to use, unless it's something I'm doing every single day. The specific instructions are quite picky and easy to bungle. Whenever possible, I prefer a GUI (Graphical User Interface) as I'm a visual person, and I find it easier to remember steps in a process when I can see what is going on (check a box, select from a pull-down, etc.).

    There are two programs I like that I'll use as illustrations. I've looked at many more than these two. The others, which I've chosen not to use, were either exceedingly difficult to install, are not intuitive in how they work, or they have to many limitations.

    Note, while I explain the process below while referring to a folder of files, you can create checksums for individual files, as well as folders, or folders of folders, up to and including entire hard drives. The only difference will be in how long it takes to create the list of checksum values, and how long it takes to verify a set of files described in that list. You may find it easier to run some tests with smaller "bite-sized" sets of files until you userstand the process and get a feel for what can be done.

    Checksum+ for OSX

    With this utility, all you have to do is drag and drop a file, multiple files or a folder on the icon in the dock. When the dialog pops up, make sure that the checkbox next to the MD5 label is ticked, and an MD5 checksum file will be created (CheckSum+ offers several options for the hashes -- there are check boxes for MD5 CSV, and SFV, but all you really need is MD5). Since the Windows program I use also does MD5, the resulting files are cross platform compatible.

    After you click the OK button, CheckSum+ goes to work. There is a progress bar, but it only will show blue in the progress bar right before it completes for some reason. If you choose a large folder, or a drive with a number of folders it may seem like the program has hung (without the infamous "spinning pizza wheel of death" showing), so resist the urge to force quit. If you are doing more than a couple hundred files, I would advise finding something else to do, as it is likely to take a while.

    If you dragged a folder onto the Checksum+ icon, then a checksum text file (ending in .md5) will be created at the folder level above the folder you chose, and will have the same name as the folder. Before you transfer the file, drag this text file (it will have the same name as the folder, but with an MD5 extension), into the folder. If you are checksumming an entire drive, then store the checksum file at the root of the hard drive.

    If you are interested, you can open this text file in a text editor, or import it into a spreadsheet. If you do, what you will see are two values, separated by some blank spaces. The first item is a 32 character string of numbers and letters (the "hash" or "checksum" value); followed by some blank spaces, and then the filename (or the path and filename) to which that hash is associated.

    Here is an example showing a RAW file and its companion XMP sidecar.

    dd33ffa352a74dd98471a4635a896e22 drp2112_030d.nef

    f0190acf1e70e22057e5d8bde3939011 drp2112_030d.xmp

    You can then transfer the folder containing the images and the newly created "Checksum" text file using whichever method you prefer. This could be to your external drive, file server, web server (you can even zip compress, then later download to a different machine and unzip).

    When you are ready to verify, simply open the folder, locate the checksum file, and drag that file with the .md5 extension to the CheckSum+ icon in the dock. In addition to MD5 files created by Checksum+ you can also drop onto checkSum+'s icon any valid md5, sfv or cvs file (other types of checksums, or verification files), and it will check for any files listed in that text file.

    The utility will then create a new checksum for each file in the folder and will then compare these to the values in the text file (the values from the original checksum process). If they all match, then you will simply see a dialogue pop up stating "All OK."

    If even one of the files in the folder doesn't match, then it will display a list of the names of all the files in the folder, and indicate which are bad, or include a full list of those that failed and those that were OK.

    As a test, after first creating a checksum for a folder, try modifying the metadata or color setting information in one of the files. After saving that file drop the MD5 file from that folder onto the icon in the dock. The results will vary depending on the application you use to make the changes. If you make changes in the Raw file using Bridge or Adobe Camera Raw, then the comparison should catch the change in the XMP sidecar, but the Raw file should show as being untouched.

    Issues with Hidden Files on Mac OS X

    One thing that does seem to happen is that CheckSum+ seems to pick up the ".DS_Store" files that are hidden in the folder if you select the folder, and/or go into the folder and "select all." So long as you recognize that this is not one of your images and are not concerned when it fails, that's not a big deal.

    MD5Summer does Windows

    For those on Windows, I would suggest taking a look at MD5Summer (http://www.md5summer.org/ ) As you might expect from it's name, this utility only creates and reads MD5 checksums. This GUI based utility is not as "drag and drop" friendly, but just about as easy to use. Instead of dragging and dropping a folder on to the program icon, you launch MD5summer and navigate to the folder you want to verify.

    Once you have selected the folder, click on Create Sums. Another dialogue will appear, where you can select the specific files to be included. As MD5summer sees "everything" you may see some files that are hidden by the OS, such as "thumbs.db" files which are created by the Microsoft "Explorer" file/folder viewer. You can use the "Select All" button and then deselect those unwanted files by holding down the Ctrl key while clicking on that file with the mouse. If you have sub-folders you will need to click the "Add Recursively" button. Note that if you do, that any "thumbs.db" files inside of those sub folders are selected automatically. There is no option to remove those, so it's easier to simply learn to just click "Select All" click "OK" and learn to ignore those files when you run the verify.

    Once you have your selection made, click on the "OK" button and MD5summer goes to work.

    After it has computed the checksum values, it will stop with a "Save As" dialogue and prompt you for what to name the file and where to save the ".md5" text file. By default it will automatically fill in the name of the folder and will save the file inside the folder you originally chose. As that is what I want, I just click on "Save" and I'm done.

    You can then transfer your files using your normal method. To verify a folder just locate the ".md5" file and right click and choose Verify with MD5summer from the contact sensitive menu.

    If even one of the images doesn't pass the verification test, you'll see a red dot appear next to the file. Any of those that pass are green. If a file doesn't verify, you'll see an error message such as, "There was 1 error while processing. Do you wish to list errors."

    If you respond by clicking "Yes" then MD5summer simply moves all the failed files to the top of the list. If you chose "No" then all of the files stay in alpha order, including the name of the folder if there are subfolders. Personally I find it easier to understand what's going on if they remain in alpha order, so I usually choose "No" at this stage.

    Other Windows Options

    Here are a couple of other Windows only options that are worth investigating.

    Checksum. "a point-and-click sha1 and md5 hashing application for windows" from Corz design (http://corz.org/windows/software/checksum/ ) has a very small footprint and interface. Unlike MD5Summer, this program does provide the option to simply right-click of a folder and choose the option to Create Checksum and a file with the hashes will appear within the chosen folder. To verify a checksum, just right-click on the MD5 or other checksum (.hash) file and choose Verify this checksum file. from the contact-sensitive menu.

    In the extreme upper right-hand corner of your screen, you will see a very thin bar noting the progress of the verification process.

    At the conclusion, you will see a small dialogue noting your success.

    If there are missing files, or files that do not match the previously created hash, the first indication of trouble is that the bar in the upper-right corner will turn red.

    And then you'll see a dialogue noting that an error log has been created and the folder will open where that log was created.

    The MD5 & SHA1 Checksum Utility1.1 was developed by Raymond Lin (http://raylin.wordpress.com/downloads/md5-sha-1-checksum-utility/ ) and can be used to manually check the hash of programs downloaded from the Internet, as well as generating and verifying checksums for folders of files. The amazing thing is that the whole program is only 52k, and doesn't require any installation. So just put a copy of the executable on a USB Jump drive, and you can use it anywhere a Windows computer is available.

    Issues with Hidden Files on Windows

    On the Windows side, your "thumbs.db" files will typically get recorded as well. As these will change as soon as you access that folder using Explorer, they will not pass verification.

    As I primarily use MD5 checksums as a means of verifying the file transfer of a single folder, I have one MD5 checksum text file that I create for each folder. There are fewer things to check if you are using the MD5summer application one folder at a time, especially if there are no subfolders.

    Notes on Cross Platform Compatibility

    If you use this method for transferring a folder of processed files to your "archive" then the MD5 checksum file can be used for several purposes. As mentioned previously you can checksum an entire drive, or a series of folders that contain subfolders as well. While it is possible to do that for an entire drive, whether this is useful or not depends on your goals and how often you modify files on that archive drive. Keep in mind that for any given session, you will only create a single checksum file, though it is possible to copy and paste parts of the text file if you are inclined to tinker.

    As the resulting checksum values are stored in a simple text file, these can be used on either the Mac or Windows platform. There are no problems using the MD5 generated by MD5summer (Windows) to check a folder that had been transferred to a Mac and verified in CheckSum+. However, if you use the MD5 Checksum file generated by Checksum+ (Mac) to check a folder that you have transferred to a Windows machine and verify with MD5Summer you will probably encounter the following error message: "The checksum file you have selected contains one or more ASCII generated sums

    (for more info, visit http://www.md5summer.org/ascii/ ). Ignore and continue?"

    If you click on the OK button the validation will run and everything works fine. This issue only concerns how the end of line return is being interpreted by the local system. So the first time you see it you might be concerned; however, as it doesn't affect the final result, you shouldn't worry.

    Other Checksum Uses

    In addition to just verifying that the files you moved from one drive to another are the same as the originals, you can use these same (or newly created) MD5 checksum files for other purposes as well.

    Check Removable Media "Health"

    If you create back-ups of your image files to CDR or DVDR, you can re-use the same MD5 file within each folder, or package all of the folders and files and create a new checksum file that can be stored at the top level of the media. With the MD5 checksum text file right there on the disc, you can accurately verify the integrity of your data right after the burn, or at any time in the future.If you suspect that your media may be failing, just pop the disc into a drive, and run a verify on the MD5 file. If you see one or more files fail, then it's time to move the rest of the files to a safer location. Once you have transferred the files (and the checksum file) to a new location, you can verify again to be sure the rest of the files are intact.

    Initially posted: July, 2010