 <p>You can create multiple encryption keys (millions) and use separate keys for separate columns. Adding multiple keys is critical for any scenario that requires periodic key rotation. To encrypt data you use <a href="http://msdn.microsoft.com/en-us/library/ms174361.aspx" rel="nofollow"><code>ENCRYPTBYKEY</code></a> and pass in the key name of the desired encryption key, see <a href="http://msdn.microsoft.com/en-us/library/ms179331.aspx" rel="nofollow">How to: Encrypt a Column of Data</a>. You decrypt data using <a href="http://msdn.microsoft.com/en-us/library/ms181860.aspx" rel="nofollow"><code>DECRYPTBYKEY</code></a>. Note that you do not specify what decryption key to use, the engine knows. But you have to properly open the decryption key first, see <a href="http://msdn.microsoft.com/en-us/library/ms190499.aspx" rel="nofollow"><code>OPEN SYMMETRIC KEY</code></a>.</p>