aes-256-cbc / encrypt integer / shorten integer in php

aes-256-cbc _ encrypt integer _ shorten integer.php

<?php
$enc=encrypt_int(3524, 'aaaa1111bbbb3333cccc5555dddd7777');
echo $enc.'<hr>';
$int=decrypt_int($enc, 'aaaa1111bbbb3333cccc5555dddd7777');
echo $int.'<hr>';
//输出: 5e91d2b65b2a<hr>3524<hr>
//输出: a08f854f3ddf<hr>3524<hr>
//...
//实际的$iv_short.$ac_short, $crypt_text 分别是:
//5e91d2b6, 5b2a
//a08f854f, 3ddf
//...
//$key需要32个字符
function encrypt_int($int, $key)
{
    $int=dechex($int);
    $int=strlen($int)%2===0?hex2bin($int):hex2bin('0'.$int);
    $hex=bin2hex(MoreUnsafeOpensslAES::encrypt($int, $key, 2, 3));
    $rtn=base_convert($hex, 16, 36);
    return $rtn;
}

function decrypt_int($enc, $key)
{
    $hex=base_convert($enc, 36, 16);
    $hex=strlen($hex)%2===0?hex2bin($hex):hex2bin('0'.$hex);
    return hexdec(bin2hex(MoreUnsafeOpensslAES::decrypt($hex, $key, 2, 3)));
}

//参考http://www.coldxiangyu.com/2017/06/27/AES%E5%8A%A0%E5%AF%86%E7%AE%97%E6%B3%95/
//只有cfb, ofb才能保持内容长度不变, 所以把aes-256-cbc降级aes-256-cfb,
//但iv还是很长, 只能对iv动手脚(减少iv len并padding), 就变得more unsafe更不安全,
//要验证机制(Authentication Code)的话还要加ac len, 至少要占3位才防刷(1600万), 剩下的iv len至少2位才能对单个数据提供6万的变动空间
//用来加密很短的自增id之类还是可以凑合一用的
class MoreUnsafeOpensslAES
{
    const METHOD = 'aes-256-cfb';
    
    public static function encrypt($message, $key, $iv_len, $ac_len)
    {
        if (mb_strlen($key, '8bit') !== 32) {
            throw new Exception("Needs a 256-bit key!");
        }
        $ivsize=openssl_cipher_iv_length(self::METHOD);
        $iv=openssl_random_pseudo_bytes($ivsize);
        $iv_short=substr($iv, 0, $iv_len);
        $ac_short=substr(hash_hmac('md5', $message.$iv_short, $key, 1), 0, $ac_len);
        $iv=str_pad($iv_short.$ac_short, $ivsize, "\0", STR_PAD_RIGHT);
        
        $ciphertext = openssl_encrypt(
            $message,
            self::METHOD,
            $key,
            OPENSSL_RAW_DATA,
            $iv
        );
        
        return $iv_short.$ac_short.$ciphertext;
    }

    public static function decrypt($message, $key, $iv_len, $ac_len)
    {
        if (mb_strlen($key, '8bit') !== 32) {
            throw new Exception("Needs a 256-bit key!");
        }
        $ivsize = openssl_cipher_iv_length(self::METHOD);
        $iv_short=mb_substr($message, 0, $iv_len, '8bit');
        $ac_short=mb_substr($message, $iv_len, $ac_len, '8bit');
        $iv=str_pad($iv_short.$ac_short, $ivsize, "\0", STR_PAD_RIGHT);

        $ciphertext = mb_substr($message, $iv_len+$ac_len, null, '8bit');
        $clear_text=openssl_decrypt(
            $ciphertext,
            self::METHOD,
            $key,
            OPENSSL_RAW_DATA,
            $iv
        );
        $tmp=substr(hash_hmac('md5', $clear_text.$iv_short, $key, 1), 0, $ac_len);

        if ($tmp!==$ac_short)
        {
            return '';
        }
        return $clear_text;
    }
}

//因为mcrypt的名字MCRYPT_RIJNDAEL_128里128是key length 128而不是block size 256, 容易搞混淆,
//以及需要自己写PKCS7 Padding等问题, 因而php里aes-256-cbc推荐的实现是用openssl写:
//参考:https://paragonie.com/blog/2015/05/if-you-re-typing-word-mcrypt-into-your-code-you-re-doing-it-wrong
class UnsafeOpensslAES
{
    const METHOD = 'aes-256-cbc';
    
    public static function encrypt($message, $key)
    {
        if (mb_strlen($key, '8bit') !== 32) {
            throw new Exception("Needs a 256-bit key!");
        }
        $ivsize = openssl_cipher_iv_length(self::METHOD);
        $iv = openssl_random_pseudo_bytes($ivsize); 
        
        $ciphertext = openssl_encrypt(
            $message,
            self::METHOD,
            $key,
            OPENSSL_RAW_DATA,
            $iv
        );
        
        return $iv . $ciphertext;
    }

    public static function decrypt($message, $key)
    {
        if (mb_strlen($key, '8bit') !== 32) {
            throw new Exception("Needs a 256-bit key!");
        }
        $ivsize = openssl_cipher_iv_length(self::METHOD);
        $iv = mb_substr($message, 0, $ivsize, '8bit');
        $ciphertext = mb_substr($message, $ivsize, null, '8bit');
        
        return openssl_decrypt(
            $ciphertext,
            self::METHOD,
            $key,
            OPENSSL_RAW_DATA,
            $iv
        );
    }
}

//整数的话用这两个函数更短小:
function shorten_int($id)
{
    $id=dechex($id);
    $id=strlen($id)%2===0?hex2bin($id):hex2bin('0'.$id);
    $id=base64_encode($id);
    $id=strtr($id, array('/'=>'_', '+'=>'-', '='=>''));
    return $id;
}

function unshorten_int($id)
{
    $id=strtr($id, array('-'=>'+', '_'=>'/'));
    $id=base64_decode($id);
    $id=bin2hex($id);
    return base_convert($id, 16, 10);
}
?>