The following functions support encryption, decryption, digital signing, and the validation of digital signatures.

 Symmetric Encryption and Decryption

EncryptByKey	DecryptByKey
EncryptByPassPhrase	DecryptByPassPhrase
Key_ID	Key_GUID

 Asymmetric Encryption and Decryption

EncryptByAsmKey	DecryptByAsmKey
EncryptByCert	DecryptByCert
Cert_ID	AsymKey_ID
CertProperty

 Signing and Signature Verification

SignByAsymKey	VerifySignedByAsmKey
SignByCert	VerifySignedByCert

 Symmetric Decryption with Automatic Key Handling

DecryptByKeyAutoCert

 See Also

Reference

Functions (Transact-SQL)
CREATE CERTIFICATE (Transact-SQL)
CREATE SYMMETRIC KEY (Transact-SQL)
CREATE ASYMMETRIC KEY (Transact-SQL)
Security Catalog Views (Transact-SQL)

Other Resources

Encryption Hierarchy
Permissions Hierarchy (Database Engine)

Help and Information

Getting SQL Server 2008 Assistance