InformationPer the Microsoft Best Practices, only the SQL Server AES algorithm options, AES_128, AES_192, and AES_256, should be used for a symmetric key encryption algorithm.
The following algorithms (as referred to by SQL Server) are considered weak or deprecated and should no longer be used in SQL Server: DES, DESX, RC2, RC4, RC4_128.
Many organizations may accept the Triple DES algorithms (TDEA) which use keying options 1 (3 key aka 3TDEA) or keying option 2 (2 key aka 2TDEA). In SQL Server, these are referred to as TRIPLE_DES_3KEY and TRIPLE_DES respectively. Additionally, the SQL Server algorithm named DESX is actually the same implementation as the TRIPLE_DES_3KEY option. However, using the DESX identifier as the algorithm type has been deprecated and its usage is now discouraged.
SolutionRefer to Microsoft SQL Server Books Online ALTER SYMMETRIC KEY entry: http://msdn.microsoft.com/en-US/library/ms189440.aspx
Eliminates use of weak and deprecated algorithms which may put a system at higher risk of an attacker breaking the key.
Encrypted data cannot be compressed, but compressed data can be encrypted. If you use compression, you should compress data before encrypting it.