You can use Symmetric Keys to encrypt data for individual users; for example, when you have one table with two sets of user data for two different users. Since each user needs access only to their own set of data, each set of user data can be encrypted with a different Symmetric Key.
All the keys should be kept in a secure place. To put it simply, if you lose a key that was used to encrypt data, you risk losing that data.
Many methods are available for data encryption. You need only select the appropriate one.
I hope these articles have given you a sound understanding of SQL Server 2005 data encryption. Now practice what you learned and write your own scripts and code using these new functions. Then explore the possibilities of using SQL Server 2005 encryption in your projects to protect your valuable data.