Sometimes clients want that the information they collected from the user should be encrypted and stored in database. Data encryption and decryption is a common technique for secured data. In this article I’ll show how could you use mysql’s built in function to encrypt and decrypt data.
Suppose you’ve a table where you want to encrypt user’s name & address. So look below the structure of the table. In this table we will store name and address as encrypted.
CREATE TABLE `user` ( `id` BIGINT UNSIGNED NOT NULL AUTO_INCREMENT , `first_name` VARBINARY(100) NULL , `address` VARBINARY(200) NOT NULL , PRIMARY KEY (`id`) ENGINE = InnoDB DEFAULT CHARACTER SET = utf8 COLLATE = utf8_general_ci
You may be expected the table structure should be:
CREATE TABLE `user` ( `id` BIGINT UNSIGNED NOT NULL AUTO_INCREMENT , `first_name` VARCHAR(50) NULL , `address` VARCHAR(100) NOT NULL , PRIMARY KEY (`id`) ENGINE = InnoDB DEFAULT CHARACTER SET = utf8 COLLATE = utf8_general_ci
To encrypt & decrypt mysql data we will use AES_ENCRYPT() and AES_DECRYPT() functions. These functions used the official AES (Advanced Encryption Standard) algorithm & encode data with a 128-bit key length. 128 bits is much faster and secure enough for most purposes.
Why we used VARBINARY data type instead of VARCHAR:
AES is a block-level algorithm. So when data encrypted it is padded. So you can calculate the length of the result string using this formula:
16 × (trunc(string_length / 16) + 1)
So if your address field structure is = VARCHAR(100) ; //100 length of varchar
Then before your encryption it should be converted
= 16 * (trunc(100/ 16) + 1)
= 16 * (6.25 + 1)
= 16 * 7.25
So VARCHAR(100) should be converted to VARBINARY(116) minimum. I suggest use little more like VARBINARY(150) in this case.
Because if AES_DECRYPT() detects invalid data or incorrect padding, it will return NULL. But it is also possible for AES_DECRYPT() to return a non-NULL value (possibly garbage) if the input data or the key is invalid.
AES_ENCRYPT(str, key_str); AES_DECRYPT(crypt_str,key_str);
Please remember, the encryption and decryption will occur based on a key. So you’ve to keep that key in a secret place and using variable you could pass the key to mysql to encrypt and decrypt data.
Now look how I insert data using AES_ENCRYPT, where I used key ‘usa2010′ :
INSERT into user (first_name, address) VALUES (AES_ENCRYPT('Obama', 'usa2010'),AES_ENCRYPT('Obama', 'usa2010'));
Now look how I decrypt data using AES_DECRYPT:
SELECT AES_DECRYPT(first_name, 'usa2010'), AES_DECRYPT(address, 'usa2010') from user;
AES_ENCRYPT() and AES_DECRYPT() can be considered the most cryptographically secure encryption functions currently available in MySQL.