CERTENCODED (Transact-SQL)

مقالة
05/16/2013

Returns the public portion of a certificate in binary format. This function takes a certificate ID and returns the encoded certificate. The binary result can be passed to CREATE CERTIFICATE … WITH BINARY to create a new certificate.

Syntax

CERTENCODED ( cert_id )

Arguments

cert_id
Is the certificate_id of the certificate. This is available from sys.certificates or by using the CERT_ID (Transact-SQL) function. cert_id is type int

Return Types

varbinary

Remarks

CERTENCODED and CERTPRIVATEKEY are used together to return different portions of a certificate in binary form.

Permissions

CERTENCODED is available to public.

Examples

Simple Example

The following example creates a certificate named Shipping04 and then uses the CERTENCODED function to return the binary encoding of the certificate.

CREATE DATABASE TEST1;
GO
USE TEST1
CREATE CERTIFICATE Shipping04 
ENCRYPTION BY PASSWORD = 'pGFD4bb925DGvbd2439587y'
WITH SUBJECT = 'Sammamish Shipping Records', 
EXPIRY_DATE = '20161031';
GO
SELECT CERTENCODED(CERT_ID('Shipping04'));

B. Copying a Certificate to Another Database

The following more complicated example, creates two databases, SOURCE_DB and TARGET_DB. The goal is to create a certificate in the SOURCE_DB, and then copy the certificate to the TARGET_DB, and then demonstrate that data encrypted in SOURCE_DB can be decrypted in TARGET_DB using the copy of the certificate.

To create the example environment, create the SOURCE_DB and TARGET_DB databases, and a master key in each. Then create a certificate in SOURCE_DB.

USE master;
GO
CREATE DATABASE SOURCE_DB;
GO
USE SOURCE_DB;
GO
CREATE MASTER KEY ENCRYPTION BY PASSWORD = 'S0URCE_DB KEY Pa$$W0rd';
GO
CREATE DATABASE TARGET_DB;
GO
USE TARGET_DB
GO
CREATE MASTER KEY ENCRYPTION BY PASSWORD = 'Pa$$W0rd in TARGET_DB';
GO

-- Create a certificate in SOURCE_DB
USE SOURCE_DB;
GO
CREATE CERTIFICATE SOURCE_CERT WITH SUBJECT = 'SOURCE_CERTIFICATE';
GO

Now extract the binary description of the certificate.

DECLARE @CERTENC VARBINARY(MAX);
DECLARE @CERTPVK VARBINARY(MAX);
SELECT @CERTENC = CERTENCODED(CERT_ID('SOURCE_CERT'));
SELECT @CERTPVK = CERTPRIVATEKEY(CERT_ID('SOURCE_CERT'),
       'CertEncryptionPa$$word');
SELECT @CERTENC AS BinaryCertificate;
SELECT @CERTPVK AS EncryptedBinaryCertificate;
GO

Create the duplicate certificate in the TARGET_DB database. You must modify the following code, inserting the two binary values returned in the previous step.

-- Create the duplicate certificate in the TARGET_DB database
USE TARGET_DB
GO
CREATE CERTIFICATE TARGET_CERT
FROM BINARY = <insert the binary value of the @CERTENC variable>
WITH PRIVATE KEY (
BINARY = <insert the binary value of the @CERTPVK variable>
, DECRYPTION BY PASSWORD = 'CertEncryptionPa$$word');
-- Compare the certificates in the two databases
-- The two certificates should be the same 
-- except for name and (possibly) the certificate_id
SELECT * FROM SOURCE_DB.sys.certificates
UNION
SELECT * FROM TARGET_DB.sys.certificates;

The following code executed as a single batch demonstrates that data encrypted in SOURCE_DB can be decrypted in TARGET_DB.

USE SOURCE_DB;

DECLARE @CLEARTEXT nvarchar(100);
DECLARE @CIPHERTEXT varbinary(8000);
DECLARE @UNCIPHEREDTEXT_Source nvarchar(100);
SET @CLEARTEXT = N'Hello World';
SET @CIPHERTEXT = ENCRYPTBYCERT(CERT_ID('SOURCE_CERT'), @CLEARTEXT);
SET @UNCIPHEREDTEXT_Source = 
    DECRYPTBYCERT(CERT_ID('SOURCE_CERT'), @CIPHERTEXT)
-- Encryption and decryption result in SOURCE_DB
SELECT @CLEARTEXT AS SourceClearText, @CIPHERTEXT AS SourceCipherText, 
       @UNCIPHEREDTEXT_Source AS SourceDecryptedText;

-- SWITCH DATABASE
USE TARGET_DB;

DECLARE @UNCIPHEREDTEXT_Target nvarchar(100);
SET @UNCIPHEREDTEXT_Target = DECRYPTBYCERT(CERT_ID('TARGET_CERT'), @CIPHERTEXT);
-- Encryption and decryption result in TARGET_DB
SELECT @CLEARTEXT AS ClearTextInTarget, @CIPHERTEXT AS CipherTextInTarget, @UNCIPHEREDTEXT_Target AS DecriptedTextInTarget; 
GO

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