<?php
/**
 * Created by PhpStorm.
 * User: Administrator
 * Date: 2018/4/1
 * Time: 1:50
 */

//註意格式一定要有下面的標識符
$pub_key = "-----BEGIN PUBLIC KEY-----
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCjwmQtK4aYLSL/aOSH4g4fdTBT1JLzeRchbR6fMylOvTjGMh4IngxCwi7NAbTm8Edr02s7HXmo7oweLfqDRHvYPz7aH5Kt6gtjGzokfIVo6nN+3jDfoNBws+pPDaro5KbeIVO0kK16m+51yPS4R3lFF6bZcrGb+xq8A/QrPHxWNQIDAQAB
-----END PUBLIC KEY-----
 
";
$pri_key = "-----BEGIN RSA PRIVATE KEY-----
MIICXQIBAAKBgQCjwmQtK4aYLSL/aOSH4g4fdTBT1JLzeRchbR6fMylOvTjGMh4IngxCwi7NAbTm8Edr02s7HXmo7oweLfqDRHvYPz7aH5Kt6gtjGzokfIVo6nN+3jDfoNBws+pPDaro5KbeIVO0kK16m+51yPS4R3lFF6bZcrGb+xq8A/QrPHxWNQIDAQABAoGAemICn8dRlVTWPO7VK8ADMftQnLXXBOJQKQj1w6BmlJPRZD18OJB1NUcN1uQZoCWeGrUsBEfo7hko2j0eZQ+/RRCanxM34l0cHP4WQLVYzZ5jGcAyFl3f6Ra4MKELGD3daynfct8z5+XsnD7Fwg/kWNWZ8NJIKHICoqBrgF6wnJkCQQDZUBhAarJsMdebDPw/wj8ovTYZWJf0oqoL+FjDsJF4p8e0MDMIGmsBTPbv5wVaF+8/EFTQ7PDhD0oWRKBpeT6/AkEAwOmgUPXWmxi/TtwjFfX7290GXERjkCwGc5Yj8bVh4YdjPl2ijaFFrogvr3gCKFDd9AD/Oz5zKcrxSl4H5sZcCwJBAMiUuD3E/fkFrFduDeqf1YI52xRcBK4F8mToDq5ZbHxsiNUVZBUHpVrm+kqG9xaoXujbnx3UhaWGYkDZiSKxiasCQQCD7MEX3KcgdbIOqfjMgeX1G5fH7XTxGUpoLVrzZwlDBCVYdww9MvbGPpfttXI0Q+klfrEMwM5c3E5afyeEKE61AkA0m6sjb5ypwXMbXo5+uSEHkpL0Qqb87SCRVV/Bli7OJNuv9DrdwVO27AA192WxUoDfC23faeeETB1Su4M785U6
-----END RSA PRIVATE KEY-----
 
";


$str = "這個是要加密的字符串888";

//這個例子是演示RSA加密
//非對稱加密 分為 公鑰和私鑰
//通常 公鑰加密 私鑰解密，私鑰加密，公鑰解密

/*
 * 用到的加密函數
openssl_private_decrypt — Decrypts data with private key
openssl_private_encrypt — Encrypts data with private key
openssl_public_decrypt — Decrypts data with public key
openssl_public_encrypt — Encrypts data with public key
 *
 
 
*/

//echo $private_key;
$pi_key =  openssl_pkey_get_private($pri_key);//這個函數可用來判斷私鑰是否是可用的，可用返回資源id Resource id
$pu_key = openssl_pkey_get_public($pub_key);//這個函數可用來判斷公鑰是否是可用的
//print_r($pi_key);echo "\n";
//print_r($pu_key);echo "\n";


//公鑰加密過程
$enStr = ‘‘;
openssl_public_encrypt($str,$enStr,$pu_key);
//加密後的字符 有些無法顯示 需要 base64_encode ( string $data ) ,解密的時候不需要要 base64_decode ( string $data )
echo base64_encode ($enStr);
echo "<br/>";


//私鑰解密過程
$deStr = ‘‘;
//$enStr = base64_decode ( $enStr);
openssl_private_decrypt($enStr,$deStr,$pi_key);
echo $deStr;
echo "<br/>";


//下面是簽名驗證例子
$binary_signature = "";
// At least with PHP 5.2.2 / OpenSSL 0.9.8b (Fedora 7)
// there seems to be no need to call openssl_get_privatekey or similar.
// Just pass the key as defined above
openssl_sign($str, $binary_signature, $pi_key, OPENSSL_ALGO_SHA1);

// Check signature
$ok = openssl_verify($str, $binary_signature, $pu_key, OPENSSL_ALGO_SHA1);
echo "check #1: ";
if ($ok == 1) {
    echo "signature ok (as it should be)\n";
} elseif ($ok == 0) {
    echo "bad (there‘s something wrong)\n";
} else {
    echo "ugly, error checking signature\n";
}

淘寶開放平臺，安全簽名就是用的此算法， 我自己（商家開發者）生成有商家私鑰和商家公鑰，支付寶那邊有支付寶私鑰和支付寶公鑰。具體是商家把商家公鑰給支付寶（支付寶用作解密和簽名驗證），我們獲取支付寶公鑰（用來對支付寶發來的信息進行解密和簽名校驗）。

註意，私鑰一定是自己用的，公鑰給其他人用.

參考地址 ： http://php.net/manual/en/function.openssl-private-decrypt.php

https://docs.open.alipay.com/58/103242

php rsa加密解密實例 及簽名驗證-自己實踐