Kredi kartı bilgieri nasıl şifrelenmiş olarka veritabanına kaydedilir(MS SQL)

kaynak: http://www.cihanozhan.com/sql-server-ile-veri-sifreleme-data-encryption/

CREATE LOGIN BankingDBLogin WITH Password = '1976';
GO
CREATE USER BankingDBUser FOR LOGIN BankingDBLogin;
go
CREATE TABLE Accounts
(
    AccountID       INT,
    FName           NVARCHAR(25),
    LName           NVARCHAR(25),
    CreditCardType      VARBINARY(1000),
    CreditCardNumber    VARBINARY(1000),
    AccountNotes        VARBINARY(MAX)
);
GO


GRANT SELECT, INSERT ON Accounts TO BankingDBUser;

CREATE MASTER KEY ENCRYPTION BY PASSWORD = '1976';


CREATE ASYMMETRIC KEY BankingDBUserAsymmetricKey AUTHORIZATION BankingDBUser
WITH ALGORITHM = RSA_2048 ENCRYPTION BY PASSWORD = '1976';


CREATE SYMMETRIC KEY BankingDBUserSymmetricKey WITH ALGORITHM = AES_256
ENCRYPTION BY ASYMMETRIC KEY BankingDBUserAsymmetricKey;

CREATE SEQUENCE [dbo].[AccountSeq] AS INT
 START WITH 1
 INCREMENT BY 1
GO


OPEN SYMMETRIC KEY BankingDBUserSymmetricKey DECRYPTION BY ASYMMETRIC KEY BankingDBUserAsymmetricKey WITH PASSWORD = '1976'  --AsymmetricKey oluşturuyoruz şifre
INSERT INTO Accounts VALUES(NEXT VALUE FOR dbo.AccountSeq, 'Vedat','Pala',
            EncryptByKey(Key_GUID('BankingDBUserSymmetricKey'),'MasterCard'),
            EncryptByKey(Key_GUID('BankingDBUserSymmetricKey'),'8961-4152-6325-9852'),
            EncryptByKey(Key_GUID('BankingDBUserSymmetricKey'),'Bilgileri gizledik.'));
CLOSE SYMMETRIC KEY BankingDBUserSymmetricKey


SELECT * FROM Accounts;


OPEN SYMMETRIC KEY BankingDBUserSymmetricKey DECRYPTION BY ASYMMETRIC KEY BankingDBUserAsymmetricKey WITH PASSWORD = '1976'  --AsymmetricKey oluşturuyoruz şifre
SELECT
    AccountID, FName, LName,
    CONVERT(VARCHAR, DecryptByKey(CreditCardType)) AS CreditCardType,
    CONVERT(VARCHAR, DecryptByKey(CreditCardNumber)) AS CreditCardNumber,
    CONVERT(VARCHAR, DecryptByKey(AccountNotes)) AS AccountNotes
FROM Accounts
CLOSE SYMMETRIC KEY BankingDBUserSymmetricKey