How can I encrypt sensitive data in the WCF configuration file?

Answer:

To encrypt sensitive data in WCF configuration file, use aspnet_regiis.exe tool.

Example: If you want to encrypt Connection String section of WCF config file, use -pe that means provider encryption .

aspnet_regiis -pe "connectionStrings" -app "/MachineDPAPI" 

-prov "DataProtectionConfigurationProvider" 

-pe means provider encryption of configuration section.
-app means your application's virtual path.
-prov means provider name

For more info: http://msdn.microsoft.com/en-us/library/k6h9cz8h(VS.80).aspx