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Verifying File Integrity using MD5 Checksum

What is MD5 Checksum ?

According to Wikipedia ,  MD5 Message-Digest Algorithm is a widely used cryptographic hash function with a 128-bit (16-byte) hash value. Specified in RFC 1321, MD5 has been employed in a wide variety of security applications, and is also commonly used to check data integrity.An MD5 hash is typically expressed as a 32-digithexadecimal number. MD5 is more commonly used these days and is used to ensure the file integrity of files that we download.

How to verify MD5 for files that we download ?

Even though there are many tools to verify MD5 , I prefer the Microsoft FCIV (File Checksum Integrity Verifier) Utility which can be download from here.Fciv is a command line utility that computes and verifies hashes of files.It computes a MD5 or SHA1 cryptographic hash of the content of the file.

The FCIV utility has the following features:

  • Supports MD5 or SHA1 hash algorithms (The default is MD5.)
  • Can output hash values to the console or store the hash value and file name in an XML file
  • Can recursively generate hash values for all files in a directory and in all subdirectories (for example, fciv.exe c:\ -r)
  • Supplies an exception list to specify files or directories to hash
  • Can store hash values for a file with or without the full path of the file
Let’s try FCIV Utility to verify MD5 & SHA1 SUM for a vSphere Hypervisor Download.
Setting up FCIV Utility :
  1. Download FCIV Utility “Windows-KB841290-x86-ENU.exe
  2. Double click Windows-KB841290-x86-ENU.exe and extract it to a folder
  3. Add the FCIV folder to the system path or else every time you execute FCIV, one has to browse to the folder where  FCIV Utility has been  extracted .
  4. Go to command prompt and type fciv.exe /?, and then press ENTER to see the various options.
Ensuring File Integrity would mean that MD5 or SHA1 SUM value displayed on the website should match with that of the downloaded file.
In our case , VMware ESXi 4.1  download page tells me the MD5 and SHA1 SUM value for the ESXi 4.1 Update1 ISO image.
Once the download is complete , Open a command prompt and calculate the MD5 or SHA1 SUM as shown below using the FCIV utility .
fciv -add  -md5
fciv -add  -sha1
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  1. Savy
    August 8, 2011 at 5:42 pm

    There is a simple application “Checksums calculator” a GUI tool to calculate md5, sha1, sha256, sha384, sha512 witch can run under Linux, Windows and MacOS x operating systems on both 32 and 64bit architectures. For more info take a look here: http://www.sinf.gr/en/hashcalc.html

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