PHP encryption extension library Mcrypt installation and examples_PHP tutorial

A brief introduction to mcrypt
When PHP programmers write code programs, in addition to ensuring the high performance of the code, there is another very important point, that is, the security of the program. In addition to several of its own encryption functions, PHP also has more comprehensive PHP encryption extension libraries Mcrypt and Mhash.
Among them, the Mcrypt extension library can realize encryption and decryption functions, that is, it can encrypt plain text and restore cipher text.
mcrypt is an important encryption support extension library in PHP. In Linux environment: this library is not enabled by default. In window environment: PHP>=5.3, mcrypt extension is enabled by default.
1. Installation of Mcrypt() library
mcypt is a very powerful encryption algorithm extension library. Mcrypt is not installed during the standard PHP installation process, but the libmcrypt.dll file is included in the PHP home directory, so we only need to remove the semicolon in front of extension=php_mcrypt.dll in this line in the PHP configuration file. , and then restart the server to use this extension library.
Supported algorithms and encryption modes
The Mcrypt library supports more than 20 encryption algorithms and 8 encryption modes, which can be displayed through the functions mcrypt_list_algorithms() and mcrypt_list_modes() [1] Encryption algorithms
Mcrypt supports The algorithms are:
cast-128
gost
rijndael-128
twofish
arcfour
cast-256
loki97
rijndael-192
saferplus
wake
blowfish-compat
des
rijndael-256
serpent
xtea
blowfish
enigma
rc2
tripledes
Encryption mode
Mcrypt The supported encryption modes are:
cbc
cfb
ctr
ecb
ncfb
nofb
ofb
stream
These algorithms and modes should be used in applications. Constants are represented by adding the prefixes MCRYPT_ and MCRYPT_ when writing, as shown in the Mcrypt application below

Example

DES algorithm is represented as MCRYPT_DES;
ECB mode is represented as MCRYPT_MODE_ECB;

Copy code The code is as follows:

$str = "What is my name? I won’t tell most people!"; //Encrypted content
$key = "key:111"; //Key
$cipher = MCRYPT_DES; //Cryptotype
$modes = MCRYPT_MODE_ECB; //Cipher mode
$iv = mcrypt_create_iv(mcrypt_get_iv_size($cipher,$modes),MCRYPT_RAND);//Initialization vector
echo "Encrypted plaintext: ".$str."

";
$str_encrypt = mcrypt_encrypt($cipher,$key,$str,$modes,$iv); //Encryption function
echo "Encrypted ciphertext:" .$str_encrypt."

";
$str_decrypt = mcrypt_decrypt($cipher,$key,$str_encrypt,$modes,$iv); //Decryption function
echo "Restore:".$str_decrypt ;
?>

Running result:
Encrypted plain text: What is my name? I don’t tell most people!
Encrypted ciphertext: 鍍??]??q???L Laugh??"? ?
Restore: My name is? I won’t tell ordinary people!
From the example It can be seen that before using the PHP encryption extension library Mcrypt to encrypt and decrypt data, an initialization vector is first created, referred to as iv. The initialization vector is created as $iv = mcrypt_create_iv(mcrypt_get_iv_size($cipher,$modes),MCRYPT_RAND); Two parameters are required: size specifies the size of iv; source is the source of iv, where the value MCRYPT_RAND is the system random number.
The function mcrypt_get_iv_size($cipher,$modes) returns the initialization vector size, and the parameters cipher and mode refers to the algorithm and encryption mode respectively.
Encryption function $str_encrypt = mcrypt_encrypt($cipher,$key,$str,$modes,$iv); The five parameters of this function are as follows: cipher—— Encryption algorithm, key - key, data (str) - data to be encrypted, mode - algorithm mode, iv - initialization vector
Decryption function mcrypt_decrypt($cipher,$key,$str_encrypt ,$modes,$iv); The parameters of this function are almost the same as those of the encryption function. The only difference is data, which means that data is the data that needs to be decrypted $str_encrypt, not the original data $str.
Note: encryption and. The parameters cipher, key and mode in the decryption function must correspond one to one, otherwise the data cannot be restored

Summary
mcrypt library constants
The Mcrypt library supports more than 20 encryption algorithms and 8 encryption modes. It can be viewed through the functions mcrypt_list_algorithms() and mcrypt_list_modes().

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