Hashing web.config credentials/connection strings

I want to apply some better security measures to an existing web application. Currently, my connection string contains the user name and password in plain text. I'm also using a custom membership provider, which stores user names and passwords in the web.config file as plain text (http://www.codeproject.com/KB/aspnet/WSSecurityProvider.aspx).
I would like to secure this information using an algorithm such as SHA1.
Could someone walk me through the best way to accomplish this? 
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