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Checksum in Windows 7

The Sedona Conference Glossary on eDiscovery terms defines Checksum as, "A value calculated on a set of data as a means of verifying its authenticity to a copy of the same set of data, usually used to ensure data was not corrupted during storage or transmission. " So a checksum function can calculate a hash value in order to confirm that a file copied from one location is identical to the version of the file in the location from which it originated.

You can do this in Windows 7 by following these steps:

1. In the folder with the source file hold down the shift key and then right click and select 'Open command window here'. See Fig. 1

2. At the command prompt enter:

CertUtil -hashfile [filename] SHA1

. . . you can also pick MD5 or SHA256. Note that SHA1 is more collision resistant than MD5, and SHA256 is more secure than SHA1.

3. Windows will generate a hash value for the file - a unique ID number of sorts that will not be the same if the file is altered even to the smallest degree. See Fig. 2

4. Change to the directory of the copy of the file you want to check by entering cd.. to get back to the root of the drive. Then enter cd [filepath] to get to the location where you copied the file.

5. Run the CheckUtil command again, and if the copying process was successful the same hash value should be returned. See Fig. 3.

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