ENCRYPTBYPASSPHRASE (Transact-SQL)

Encrypt data with a passphrase.

Topic link iconTransact-SQL Syntax Conventions

Syntax

EncryptByPassPhrase ( { 'passphrase' | @passphrase } 
    , { 'cleartext' | @cleartext }
  [ , { add_authenticator | @add_authenticator }
    , { authenticator | @authenticator } ] )

Arguments

  • passphrase
    A passphrase from which to generate a symmetric key.

  • **@passphrase**
    A variable of type nvarchar, char, varchar, binary, varbinary, or nchar containing a passphrase from which to generate a symmetric key.

  • cleartext
    The cleartext to be encrypted.

  • **@cleartext**
    A variable of type nvarchar, char, varchar, binary, varbinary, or nchar containing the cleartext. Maximum size is 8,000 bytes.

  • add_authenticator
    Indicates whether an authenticator will be encrypted together with the cleartext. 1 if an authenticator will be added. int.

  • **@add\_authenticator**
    Indicates whether a hash will be encrypted together with the cleartext.

  • authenticator
    Data from which to derive an authenticator. sysname.

  • **@authenticator**
    A variable containing data from which to derive an authenticator.

Return Types

varbinary with maximum size of 8,000 bytes.

Remarks

A passphrase is a password that includes spaces. The advantage of using a passphrase is that it is easier to remember a meaningful phrase or sentence than to remember a comparably long string of characters.

This function does not check password complexity.

Examples

The following example updates a record in the SalesCreditCard table and encrypts the value of the credit card number stored in column CardNumber_EncryptedbyPassphrase, using the primary key as an authenticator.

USE AdventureWorks;
GO
-- Create a column in which to store the encrypted data.
ALTER TABLE Sales.CreditCard 
    ADD CardNumber_EncryptedbyPassphrase varbinary(256); 
GO
-- First get the passphrase from the user.
DECLARE @PassphraseEnteredByUser nvarchar(128);
SET @PassphraseEnteredByUser 
    = 'A little learning is a dangerous thing!';

-- Update the record for the user's credit card.
-- In this case, the record is number 3681.
UPDATE Sales.CreditCard
SET CardNumber_EncryptedbyPassphrase = EncryptByPassPhrase(@PassphraseEnteredByUser
    , CardNumber, 1, CONVERT( varbinary, CreditCardID))
WHERE CreditCardID = '3681';
GO