Encrypts data with an asymmetric key.

Topic link iconTransact-SQL Syntax Conventions


EncryptByAsymKey (Asym_Key_ID, { 'plaintext' | @plaintext } )


  • Asym_Key_ID
    Is the ID of an asymmetric key in the database. int.

  • cleartext
    Is a string of data that will be encrypted with the asymmetric key.

  • **@plaintext**
    Is a variable of type nvarchar, char, varchar, binary, varbinary, or nchar that contains data to be encrypted with the asymmetric key.

Return Types

varbinary with a maximum size of 8,000 bytes.


Encryption and decryption with an asymmetric key is very costly compared with encryption and decryption with a symmetric key. We recommend that you not encrypt large datasets, such as user data in tables, using an asymmetric key. Instead, you should encrypt the data using a strong symmetric key and encrypt the symmetric key using an asymmetric key.


The following example encrypts the text stored in @cleartext with the asymmetric key JanainaAsymKey02. The encrypted data is inserted into the ProtectedData04 table.

INSERT INTO [AdventureWorks].[Sales].[ProtectedData04] 
    values( N'data encrypted by asymmetric key ''JanainaAsymKey02''',
    EncryptByAsymKey(AsymKey_ID('JanainaAsymKey02'), @cleartext) )