Use discuz's encryption function authcode to prevent ticket fraud_PHP tutorial

I recently conducted a poll and needed to take measures to prevent vote fraud. But it is difficult to prevent ticket fraud, after all, there are many ways to do it. In order to prevent ticket fraud to the greatest extent, this method was used.

First define a string 'www.bkjia.com' on the front page, and then use discuz's authcode function to generate a string of ciphertext. This string of ciphertext is different every time, for example,

will be generated

• 10884NwIMCg5nDZ24rarNv+nBpsWut6ReT1grxHH4oKSdvgPmXJ0z2jEuePCe
• a8b4XU3yBHEec48KirVf0N3VAXKIQHm1qvwvpCYUu6ywwQJLR0ErlI1zwfG7tQ

But after decoding in the background, the plaintext of the reply will eventually change back to 'www.bkjia.com'. Using this, we can judge on the server side. If the returned ciphertext is not that string after decoding, voting will not be possible. .

discuz’s authcode function can be said to have made a significant contribution to the PHP community in China. Including Kangsheng's own products, as well as most Chinese companies using PHP, use this function for encryption. Authcode uses XOR operations for encryption and decryption.

The principle is as follows, if:

Encryption

• Plain text: 1010 1001
• Key: 1110 0011
• Cryptotext: 0100 1010

The ciphertext is 0100 1010. To decrypt it, just XOR it with the key

Decryption

• Cryptotext: 0100 1010
• Key: 1110 0011
• Clear text: 1010 1001

There is no sophisticated algorithm, the key is very important, so the key lies in how to generate the key. Then let’s take a look at how Kangsheng’s authcode is done:

<?php
// 参数解释
// $string： 明文 或 密文
// $operation：DECODE表示解密,其它表示加密
// $key： 密匙
// $expiry：密文有效期
function authcode($string, $operation = 'DECODE', $key = '', $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
    // 加入随机密钥，可以令密文无任何规律，即便是原文和密钥完全相同，加密结果也会每次不同，增大破解难度。
    // 取值越大，密文变动规律越大，密文变化 = 16 的 $ckey_length 次方
    // 当此值为 0 时，则不产生随机密钥
    $ckey_length = 4;
 
    // 密匙
    $key = md5($key ? $key : $GLOBALS['discuz_auth_key']);
 
    // 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 == 'DECODE' ? substr($string, 0, $ckey_length): substr(md5(microtime()), -$ckey_length)) : '';
    // 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 = $operation == 'DECODE' ? base64_decode(substr($string, $ckey_length)) : sprintf('0d', $expiry ? $expiry + time() : 0).substr(md5($string.$keyb), 0, 16).$string;
    $string_length = strlen($string);
    $result = '';
    $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($operation == 'DECODE') {
        // substr($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 '';
        }
    } 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 $keyc.str_replace('=', '', base64_encode($result));
    }
}

// 加密
echo authcode("www.bkjia.com", 'ENCODE');
// 解密
echo authcode(authcode("www.bkjia.com", 'ENCODE'));
//echo authcode("55e5OxJ5zjgFuqTjFRPdt9ag+fC+GKP9Efq6yWeAAvdQFq+D");
?>

http://www.bkjia.com/PHPjc/752395.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/752395.htmlTechArticleA poll was recently conducted, and measures to prevent vote fraud need to be taken. But it is difficult to prevent ticket fraud, after all, there are many ways to do it. In order to prevent ticket fraud to the greatest extent, this method was used. First...