Browse the MS Enterprise Library: Cryptography Application Block : Page 2

Hash Provider Configuration

You need a hash provider in order to calculate the hash value of some given data. This approach is often used for safely storing passwords in a data store: the application calculates the hash value of the provided password and stores this hash value in the database. When the user enters his password again, the system calculates the hash value of the current password and compares it to the stored hash value. When both hash values match, the user entered the correct password. Otherwise, he entered a wrong password.

The only disadvantage of this solution is that you can't recreate the password from the hash value stored in the database. So, for example, you can't email the password to the user when he forgets it. Table 2 lists the two hash providers available in the Cryptography Application Block.

Algorithm Provider	Description
Custom Hash Provider	This provider enables you to implement your own hash provider with your own underlying algorithm.
HashAlgorithmProvider	This provider uses a hash provider provided by the Cryptography Application Block.

Table 2. Hash Providers Available in Cryptography Application Block

When you use the HashAlgorithmProvider you can use the following hash algorithms:

• HMACSHA1 – Hash-based Message Authentication Code (HMAC) using the SHA1 hash algorithm
• MACTripleDES – Message Authentication Code (MAC) using the Triple DES hash algorithm
• MD5CryptoServiceProvider – The MD5 hash algorithm CSP
• SHA1CryptoServiceProvider – The SHA1 hash algorithm CSP
• SHA1Managed – The SHA1 hash algorithm CSP for input data using the managed library
• SHA256Managed – The SHA246 hash algorithm CSP for input data using the managed library
• SHA384Managed – The SHA384 hash algorithm CSP for input data using the managed library
• SHA512Managed – The SHA512 hash algorithm CSP for input data using the managed library

You must also give the hash providers a unique name, as you do with the symmetric providers described previously.

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