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Cryptographic Hash Algorithms Sample

Visual Studio 2008

This sample demonstrates how to use hash functions to ensure data integrity.

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Security noteSecurity Note:

This sample code is intended to illustrate a concept, and it shows only the code that is relevant to that concept. It may not meet the security requirements for a specific environment, and it should not be used exactly as shown. We recommend that you add security and error-handling code to make your projects more secure and robust. Microsoft provides this sample code "AS IS" with no warranties.

To run this sample

  • Press F5.

The application compares two hash values: the hash value of text in a file to the hash value of text in a TextBox control. Hash values are unique and compact numeric representations of a piece of data. The text file is an XML version of the Products table of the Northwind database. When the application starts, the XML file, stored in My.Resources, is retrieved and loaded into the TextBox control. The hash value for the XML file is calculated. When you click the Compare! button, the hash value of the TextBox text is calculated. If you have not changed the text in the TextBox control, the hash values will match. Changing even one character in a source file changes the hash value.

The RadioButton controls determine the type of hash calculated: MD5, SHA1, or SHA384. A separate .NET Framework class, derived from the HashAlgorithm class, exists for each hash algorithm. These classes are used to calculate the hash values.