Column Encryption - SQL Server to Aurora PostgreSQL Migration Playbook
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Column Encryption

Feature compatibility Amazon SCT / Amazon DMS automation level Amazon SCT action code index Key differences


                              Three star feature compatibility

N/A

N/A

Syntax and option differences, similar functionality.

SQL Server Usage

SQL Server provides encryption and decryption functions to secure the content of individual columns. The following list identifies common encryption functions:

  • EncryptByKey and DecryptByKey.

  • EncryptByCert and DecryptByCert.

  • EncryptByPassPhrase and DecryptByPassPhrase.

  • EncryptByAsymKey and DecryptByAsymKey.

You can use these functions anywhere in your code; they aren’t limited to encrypting table columns. A common use case is to increase run time security by encrypting of application user security tokens passed as parameters.

These functions follow the general SQL Server encryption hierarchy, which in turn use the Windows Server Data Protection API.

Symmetric encryption and decryption consume minimal resources. You can use them for large data sets.

Note

This section doesn’t cover Transparent Data Encryption (TDE) or Always Encrypted end-to-end encryption.

Syntax

General syntax for EncryptByKey and DecryptByKey:

EncryptByKey ( <key GUID> , { 'text to be encrypted' }, { <use authenticator flag>}, { <authenticator> } );
DecryptByKey ( 'Encrypted Text' , <use authenticator flag>, { <authenticator> )

Examples

The following examples demonstrate how to encrypt an employee Social Security Number.

Create a database master key.

USE MyDatabase;
CREATE MASTER KEY
ENCRYPTION BY PASSWORD = '<MyPassword>';

Create a certificate and a key.

CREATE CERTIFICATE Cert01
WITH SUBJECT = 'SSN';
CREATE SYMMETRIC KEY SSN_Key
WITH ALGORITHM = AES_256
ENCRYPTION BY CERTIFICATE Cert01;

Create an Employees table.

CREATE TABLE Employees
(
  EmployeeID INT PRIMARY KEY,
  SSN_encrypted VARBINARY(128) NOT NULL
);

Open the symmetric key for encryption.

OPEN SYMMETRIC KEY SSN_Key
DECRYPTION BY CERTIFICATE Cert01;

Insert the encrypted data.

INSERT INTO Employees (EmployeeID, SSN_encrypted)
VALUES
(1, EncryptByKey(Key_GUID('SSN_Key') , '1112223333', 1, HashBytes('SHA1', CONVERT(VARBINARY, 1)));
SELECT EmployeeID,
CONVERT(CHAR(10), DecryptByKey(SSN, 1 , HashBytes('SHA1', CONVERT(VARBINARY, EmployeeID)))) AS SSN
FROM Employees;

EmployeeID  SSN_Encrypted              SSN
1           0x00F983FF436E32418132...  1112223333

For more information, see Encrypt a Column of Data and Encryption Hierarchy in the SQL Server documentation.

PostgreSQL Usage

Amazon Aurora PostgreSQL-Compatible Edition (Aurora PostgreSQL) provides encryption and decryption functions similar to SQL Server using the pgcrypto extension. To use this feature, you must first install the pgcrypto extension.

CREATE EXTENSION pgcrypto;

Aurora PostgreSQL supports many encryption algorithms:

  • MD5

  • SHA1

  • SHA224/256/384/512

  • Blowfish

  • AES

  • Raw encryption

  • PGP Symmetric encryption

  • PGP Public-Key encryption

This section describes the use of PGP_SYM_ENCRYPT and PGP_SYM_DECRYPT, but there are many more options available. For more information, see the link and the end of this section.

Syntax

Encrypt columns using PGP_SYM_ENCRYPT.

pgp_sym_encrypt(data text, psw text [, options text ]) returns bytea
pgp_sym_decrypt(msg bytea, psw text [, options text ]) returns text

Examples

The following examples demonstrate how to encrypt an employee’s Social Security Number.

Create the users table.

CREATE TABLE users (id SERIAL, name VARCHAR(60), pass TEXT);

Insert the encrypted data.

INSERT INTO users (name, pass) VALUES ('John',PGP_SYM_ENCRYPT('123456', 'AES_KEY'));

Verify the data is encrypted.

SELECT * FROM users;

id  name  pass
2   John  \xc30d04070302c30d07ff8b3b12f26ad233015a72bab4d3bb73f5a80d5187b1b043149dd961da58e76440ca9eb4a5f7483cc8ce957b47e39b143cf4b1192bb39

Query using the encryption key.

SELECT name, PGP_SYM_DECRYPT(pass::bytea, 'AES_KEY') as pass
FROM users WHERE (name LIKE '%John%');

name  pass
John  123456

Update the data.

UPDATE users SET (name, pass) = ('John',PGP_SYM_ENCRYPT('0000', 'AES_KEY')) WHERE id='2';

SELECT name, PGP_SYM_DECRYPT(pass::bytea, 'AES_KEY') as pass
  FROM users WHERE (name LIKE '%John%');

name  pass
John  0000

For more information, see pgcrypto in the PostgreSQL documentation.