Microsoft SQL Server Encryption Encryption by certificate
Example
CREATE CERTIFICATE My_New_Cert
FROM FILE = 'D:\Temp\CertTest\certificateDER.cer'
GO
Create the certificate
SELECT EncryptByCert(Cert_ID('My_New_Cert'),
'This text will get encrypted') encryption_test
Usually, you would encrypt with a symmetric key, that key would get encrypted by the asymmetric key (public key) from your certificate.
Also, note that encryption is limited to certain lengths depending on key length and returns NULL otherwise. Microsoft writes: "The limits are: a 512 bit RSA key can encrypt up to 53 bytes, a 1024 bit key can encrypt up to 117 bytes, and a 2048 bit key can encrypt up to 245 bytes."
EncryptByAsymKey has the same limits. For UNICODE this would be divided by 2 (16 bits per character), so 58 characters for a 1024 bit key.
