php实现MD5withRSA签名算法

<?php

class Md5RSA{

    /**
     * 利用约定数据和私钥生成数字签名
     * @param $data 待签数据
     * @return String 返回签名
     */
    public function sign($data="")
    {
        if (empty($data))
        {
            return False;
        }

        $private_key = file_get_contents(dirname(__FILE__)."/rsa_private_key.pem");
        if (empty($private_key))
        {
            echo "Private Key error!";
            return False;
        }

        $pkeyid = openssl_get_privatekey($private_key);
        if (empty($pkeyid))
        {
            echo "private key resource identifier False!";
            return False;
        }

        $verify = openssl_sign($data, $signature, $pkeyid, OPENSSL_ALGO_MD5);
        openssl_free_key($pkeyid);
        return $signature;
    }

    /**
     * 利用公钥和数字签名以及约定数据验证合法性
     * @param $data 待验证数据
     * @param $signature 数字签名
     * @return -1:error验证错误 1:correct验证成功 0:incorrect验证失败
     */
    public function isValid($data="", $signature="")
    {
        if (empty($data) || empty($signature))
        {
            return False;
        }

        $public_key = file_get_contents(dirname(__FILE__)."/rsa_public_key.pem");
        if (empty($public_key))
        {
            echo "Public Key error!";
            return False;
        }

        $pkeyid = openssl_get_publickey($public_key);
        if (empty($pkeyid))
        {
            echo "public key resource identifier False!";
            return False;
        }

        $ret = openssl_verify($data, $signature, $pkeyid, OPENSSL_ALGO_MD5);
        switch ($ret)
        {
            case -1:
                echo "error";
                break;
            default:
                echo $ret==1 ? "correct" : "incorrect";//0:incorrect
                break;
        }
        return $ret;
    }

}

不知道怎么获得RSA公钥和私钥的先看这篇 http://www.cnblogs.com/kennyhr/p/3746048.html

不清楚RSA算法的推荐看阮老师的http://www.ruanyifeng.com/blog/2013/06/rsa_algorithm_part_one.html