Example analysis of the classic encryption method of discuz content in PHP encryption

This article mainly introduces the classic encryption method of discuz content in PHP encryption, and analyzes the usage techniques of discuz encryption in detail with specific examples. It has certain reference value. Friends in need can refer to this article

The example describes the classic encryption method of discuz content in PHP encryption. Share it with everyone for your reference, the details are as follows:

Introduction: Sometimes, we want to encrypt certain sensitive fields in the table. We have thought about it for a long time but there is no better solution. The background is online I checked it out and found that this solution from the discuz forum can solve this situation well. I specially copied it and shared it with you. The code is as follows:

header ( "Content-type:text/html;charset=UTF-8" );
echo $string='花园路888号';
echo &#39;<hr/>加密有效期10秒,密文内容:&#39;;
// $string=&#39;1111&#39;;
$sss=authcode($string,&#39;&#39;,&#39;&#39;,10);
echo $sss;
echo &#39;<hr/>加密后立即解密:...&#39;;
echo authcode($sss);
sleep(6);
echo &#39;<hr/>6秒后解密...&#39;;
$aaaa=authcode($sss);
var_dump($aaaa);
sleep(5);
echo &#39;<hr/>再次5秒后解密...&#39;;
$aaaa=authcode($sss);
var_dump($aaaa);
/**
 *
 * @param string $string    明文或密文字符串
 * @param string $operation    DECODE表示解密,其它表示加密
 * @param string $key    密钥
 * @param int $expiry    密文有效期,0代码永不过期
 * @return string
 */
function authcode($string, $operation = &#39;DECODE&#39;, $key = &#39;&#39;, $expiry = 0) {
    // 动态密匙长度，相同的明文会生成不同密文就是依靠动态密匙
    $ckey_length = 4;
    // 密匙
    $key = md5 ( $key ? $key : $GLOBALS [&#39;discuz_auth_key&#39;] );
    // 密匙a会参与加解密
    $keya = md5 ( substr ( $key, 0, 16 ) );
    // 密匙b会用来做数据完整性验证
    $keyb = md5 ( substr ( $key, 16, 16 ) );
    // 密匙c用于变化生成的密文
    $keyc = $ckey_length ? ($operation == &#39;DECODE&#39; ? substr ( $string, 0, $ckey_length ) : substr ( md5 ( microtime () ), - $ckey_length )) : &#39;&#39;;
    // 参与运算的密匙
    $cryptkey = $keya . md5 ( $keya . $keyc );
    $key_length = strlen ( $cryptkey );
    // 明文，前10位用来保存时间戳，解密时验证数据有效性，10到26位用来保存$keyb(密匙b)，解密时会通过这个密匙验证数据完整性
    // 如果是解码的话，会从第$ckey_length位开始，因为密文前$ckey_length位保存 动态密匙，以保证解密正确
    $string = $operation == &#39;DECODE&#39; ? base64_decode ( substr ( $string, $ckey_length ) ) : sprintf ( &#39;0d&#39;, $expiry ? $expiry + time () : 0 ) . substr ( md5 ( $string . $keyb ), 0, 16 ) . $string;
    $string_length = strlen ( $string );
    $result = &#39;&#39;;
    $box = range ( 0, 255 );
    $rndkey = array ();
    // 产生密匙簿
    for($i = 0; $i <= 255; $i ++) {
        $rndkey [$i] = ord ( $cryptkey [$i % $key_length] );
    }
    // 用固定的算法，打乱密匙簿，增加随机性，好像很复杂，实际上对并不会增加密文的强度
    for($j = $i = 0; $i < 256; $i ++) {
        $j = ($j + $box [$i] + $rndkey [$i]) % 256;
        $tmp = $box [$i];
        $box [$i] = $box [$j];
        $box [$j] = $tmp;
    }
    // 核心加解密部分
    for($a = $j = $i = 0; $i < $string_length; $i ++) {
        $a = ($a + 1) % 256;
        $j = ($j + $box [$a]) % 256;
        $tmp = $box [$a];
        $box [$a] = $box [$j];
        $box [$j] = $tmp;
        // 从密匙簿得出密匙进行异或，再转成字符
        $result .= chr ( ord ( $string [$i] ) ^ ($box [($box [$a] + $box [$j]) % 256]) );
    }
    if ($operation == &#39;DECODE&#39;) {
        // substr($result, 0, 10) == 0 验证数据有效性
        // substr($result, 0, 10) - time() > 0 验证数据有效性
        // substr($result, 10, 16) == substr(md5(substr($result, 26).$keyb), 0,
        // 16) 验证数据完整性
        // 验证数据有效性，请看未加密明文的格式
        if ((substr ( $result, 0, 10 ) == 0 || substr ( $result, 0, 10 ) - time () > 0) && substr ( $result, 10, 16 ) == substr ( md5 ( substr ( $result, 26 ) . $keyb ), 0, 16 )) {
            return substr ( $result, 26 );
        } else {
            return &#39;&#39;;
        }
    } else {
        // 把动态密匙保存在密文里，这也是为什么同样的明文，生产不同密文后能解密的原因
        // 因为加密后的密文可能是一些特殊字符，复制过程可能会丢失，所以用base64编码
        return $keyc . str_replace ( &#39;=&#39;, &#39;&#39;, base64_encode ( $result ) );
    }
}

The result of running the above code:

花园路888号
加密有效期10秒,密文内容:ce9eelLd6jpd7hZJTRg+/fgg8cD9VG+1NsHvkavEKhdvhk7jcfDoQTYSAAw
加密后立即解密:...花园路888号
6秒后解密...
string'花园路888号' (length=15)
再次5秒后解密...
string'' (length=0)

The above is the entire content of this article, I hope it will be helpful to everyone's study.

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