Mssql 2005 has provides a lot of encrption function: PassPhrase, synrommetric, asymmetric and encryption by certificate.
PassPhrase function is basicaly method for data encryption. It’s use e user defined decryption key.

Encrypting data by PassPhrase:

Declare @EncryptedData varbinary(MAX)
Select @EncryptedData = EncryptByPassPhrase('cenq', 'mypassword' )
Select @EncryptedData