Enterprise Library Test Guide - Willy .Net

Using the Test Cases 249
Solution
The solution was to zero out the unencrypted algorithm key before returning the
data. The application block code was modified by adding the CryptographyUtility.
ZeroOutBytes method. The following is the modified code.
public byte[] Decrypt(byte[] encryptedText)
{
byte[] output = null;
byte[] data = ExtractIV(encryptedText);
this.algorithm.Key = Key;
using (ICryptoTransform transform = this.algorithm.CreateDecryptor())
{
output = Transform(transform, data);
}
CryptographyUtility.ZeroOutBytes(this.algorithm.Key);
return output;
}
Verification
The CryptographyUtility.ZeroOutBytes method was examined to verify that it
cleared the algorithm key, which is contained in a byte array. The method incorporates
the .NET Framework Array.Clear method, which clears byte arrays.
public static void ZeroOutBytes(byte[] bytes)
{
if (bytes == null)
{
return;
}
Array.Clear(bytes, 0, bytes.Length);
}
Functional Testing
The objective of the functional tests is to verify that the application block meets all
of its functional requirements. This section discussions functional issues that were
found in the Cryptography Application Block, the Data Access Application Block,
the Exception Handling Application Block, the Logging Application Block, and the
Security Application Block.
Testing the Cryptography Application Block
This test case determined whether the Cryptography Application Block would encrypt
data when the data protection scope was set to LocalMachine and there was no
entropy.