des加密是對稱加密中在網際網路應用的比較多的一種加密方式，php 通過mcrypt擴充套件庫來支援des加密，要在Php中使用des加密，需要先安裝mcrypt擴充套件庫

下面是加密解密的例項

$iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_ECB);
$iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);
$key = "This is a very secret key";//金鑰
$text = "Meet me at 11 o'clock behind the monument.";//需要加密的內容
echo ($text) . "\n";

$crypttext =base64_encode(mcrypt_encrypt(MCRYPT_RIJNDAEL_256, $key, $text, MCRYPT_MODE_ECB, $iv));
echo $crypttext . "\n";//加密後的內容

echo mcrypt_decrypt(MCRYPT_RIJNDAEL_256,$key,base64_decode($crypttext),MCRYPT_MODE_ECB,$iv);//解密後的內容
 

在AES加密演算法中通常會用到MCRYPT_RIJNDAEL_128、MCRYPT_RIJNDAEL_192、MCRYPT_RIJNDAEL_256三種，後面的128、192、256代表的是祕鑰（也就是加密的Key）是多少bit的，比如使用的是MCRYPT_RIJNDAEL_128，那麼用這個演算法加密時祕鑰長度就是128bit的，比如 $key = 'fjjda0&9^$$#+*%$fada'，是20個字元，那在實際加密的時候只用到前16個字元加密（16*8=128）,不足128bit的php中會用'\0'來補齊。

有的時候做專案對接的時候，可能你用的是Php加密的，而對方用的是java寫的，對接的過程中就發現機加密後的內容對方解密不了，這是因為Php跟java在實現這個演算法的時候有差別，要想正確加密解密需要兩邊都做下處理：

PHP:

<?php
class Security {
	public static function encrypt($input, $key) {
        $size = mcrypt_get_block_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_ECB);
        $input = Security::pkcs5_pad($input, $size);
        $td = mcrypt_module_open(MCRYPT_RIJNDAEL_128, '', MCRYPT_MODE_ECB, '');
        $iv = mcrypt_create_iv (mcrypt_enc_get_iv_size($td), MCRYPT_RAND);
        mcrypt_generic_init($td, $key, $iv);
        $data = mcrypt_generic($td, $input);
        mcrypt_generic_deinit($td);
        mcrypt_module_close($td);
        $data = base64_encode($data);
        return $data;
	}
 
	private static function pkcs5_pad ($text, $blocksize) {
		$pad = $blocksize - (strlen($text) % $blocksize);
		return $text . str_repeat(chr($pad), $pad);
	}
 
	public static function decrypt($sStr, $sKey) {
		$decrypted= mcrypt_decrypt(
		MCRYPT_RIJNDAEL_128,
		$sKey,
		base64_decode($sStr),
		MCRYPT_MODE_ECB
	);
 
		$dec_s = strlen($decrypted);
		$padding = ord($decrypted[$dec_s-1]);
		$decrypted = substr($decrypted, 0, -$padding);
		return $decrypted;
	}	
}
 
 
 
$key = "1234567891234567";
$data = "example";
 
$value = Security::encrypt($data , $key );
echo $value.'<br/>';
echo Security::decrypt($value, $key );
 

import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
 
import org.apache.commons.codec.binary.Base64;
 
public class Security {
	public static String encrypt(String input, String key){
        byte[] crypted = null;
        try{
            SecretKeySpec skey = new SecretKeySpec(key.getBytes(), "AES");
            Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
            cipher.init(Cipher.ENCRYPT_MODE, skey);
            crypted = cipher.doFinal(input.getBytes());
        }catch(Exception e){
        System.out.println(e.toString());
	}
	return new String(Base64.encodeBase64(crypted));
}
 
    public static String decrypt(String input, String key){
        byte[] output = null;
        try{
            SecretKeySpec skey = new SecretKeySpec(key.getBytes(), "AES");
            Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
            cipher.init(Cipher.DECRYPT_MODE, skey);
            output = cipher.doFinal(Base64.decodeBase64(input));
            }catch(Exception e){
            System.out.println(e.toString());
        }
        return new String(output);
    }
 
	public static void main(String[] args) {
		String key = "1234567891234567";
		String data = "example";
		
		System.out.println(Security.encrypt(data, key));
		
		System.out.println(Security.decrypt(Security.encrypt(data, key), key));
		
			
	}	
}