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Leaving passwords unencrypted in a configuration file is generally considered a bad idea. Although some level of access is required to get to the file, encrypting the passwords—especially database passwords—adds a layer of security. However, implementing this type of encryption has been a bit difficult until ASP.NET 2.0. Microsoft provided the Data Protection API prior to 2.0, but did not provide a .NET interface to these methods.
With ASP.NET 2.0, you now have the ability to encrypt portions of your configuration file by using the aspnet_regiis.exe utility, located in the \Windows\Framework\v2.0.50727 folder (assuming your Windows root is \Windows). Unfortunately, the Microsoft documentation makes using this command much harder than it really needs to be. By using this simple command, you can pick a section (such as connectionStrings, appSettings, and so forth) in your Web.config file to encrypt:
aspnet_regiis -pef appSettings C:\Inetpub\wwwroot\mysite
This encrypts the section of your configuration file. The -pdf option decrypts it:
aspnet_regiis -pdf appSettings C:\Inetpub\wwwroot\mysite
This will work with any of the built-in sections under the configuration node. You need to do the encryption and decryption on the same machine, unless you take some extra steps to create a shared key that can be used in a server farm, for instance. The Microsoft documentation provides more examples on the more complicated methods of using this code.
Although this is handy for built-in sections, my own testing showed that it does not work properly with custom configuration sections that you may have defined on your own. I'll continue to search for an answer and provide it in a future tip if I find it.
About the Author
Eric Smith is the owner of Northstar Computer Systems, a Web-hosting company based in Indianapolis, Indiana. He is also a MCT and MCSD who has been developing with .NET since 2001. In addition, he has written or contributed to 12 books covering .NET, ASP, and Visual Basic. Send him your questions and feedback via e-mail at firstname.lastname@example.org.