Data encryption techniques in PHP

PHP, as a server-side scripting language, is often used to process sensitive data. Data encryption is very important when transmitting or storing sensitive data. This article will introduce techniques for data encryption in PHP.

1. Encryption using a hash function

A hash function is a function that compresses a message of any length into a fixed-length digest. PHP has built-in common hash functions, such as md5(), sha1(), etc.

The following is an example of hashing the password using SHA256:

$password = 'password123'; 
$hashedPassword = hash('sha256', $password); //加密后的密码

The advantage of using the hash function for encryption is that after the password is encrypted, it cannot be decrypted back to plain text. Can be verified.

2. Symmetric encryption

Symmetric encryption refers to an encryption method that uses the same key for encryption and decryption. Implementing symmetric encryption in PHP can use the openssl extension. Symmetric encryption functions include openssl_encrypt() and openssl_decrypt().

The following is a sample code:

$data = "这是一段敏感内容";

$method = 'AES-256-CBC';
$key = md5('my_secret_key');
$iv = md5('my_iv');

//加密
$encrypted_data = openssl_encrypt($data, $method, $key, 0, $iv);

//解密
$decrypted_data = openssl_decrypt($encrypted_data, $method, $key, 0, $iv);

In this sample code, the AES-256-CBC algorithm is used for encryption. Among them, the key uses the md5 hash algorithm to process "my_secret_key", and the IV uses the md5 hash algorithm to process "my_iv".

It should be noted that when using symmetric encryption, the security of the key needs to be ensured, otherwise the key may be obtained by hackers and cracked.

3. Asymmetric encryption

In asymmetric encryption, different keys are used for encryption and decryption. Asymmetric encryption can be implemented in PHP using the openssl extension. The main functions of asymmetric encryption are openssl_public_encrypt(), openssl_private_decrypt(), openssl_private_encrypt() and openssl_public_decrypt().

The following is a sample code:

$data = "这是一段敏感内容";

//生成密钥对
$config = array(
    "digest_alg" => "sha512",
    "private_key_bits" => 2048,
    "private_key_type" => OPENSSL_KEYTYPE_RSA,
);
$res = openssl_pkey_new($config);
openssl_pkey_export($res, $private_key);
$public_key = openssl_pkey_get_details($res);
$public_key = $public_key["key"];

//加密
openssl_public_encrypt($data, $encrypted, $public_key);

//解密
openssl_private_decrypt($encrypted, $decrypted, $private_key);

In this sample code, a pair of RSA public and private keys is first generated, then the public key is used for encryption, and the private key is used for decryption.

It should be noted that in asymmetric encryption, the private key needs to be kept properly, otherwise there is a risk of being leaked.

To sum up, the data encryption techniques in PHP include hash function encryption, symmetric encryption and asymmetric encryption. In practical applications, we need to choose the appropriate encryption method according to the specific situation and ensure the security of the key.

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