/**
 * RSA私鑰加密
 * @param string $private_key 私鑰
 * @param string $data 要加密的字符串
 * @return string $encrypted 返回加密后的字符串
 * @author mosishu
 */
function privateEncrypt($private_key,$data){
 $encrypted = '';
 $pi_key = openssl_pkey_get_private($private_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
 //最大允許加密長度為117，得分段加密
 $plainData = str_split($data, 100);//生成密鑰位數 1024 bit key
 foreach($plainData as $chunk){
  $partialEncrypted = '';
  $encryptionOk = openssl_private_encrypt($chunk,$partialEncrypted,$pi_key);//私鑰加密
  if($encryptionOk === false){
   return false;
  }
  $encrypted .= $partialEncrypted;
 }
 
 $encrypted = base64_encode($encrypted);//加密后的內容通常含有特殊字符，需要編碼轉換下，在網絡間通過url傳輸時要注意base64編碼是否是url安全的
 return $encrypted;
}

/**
 * RSA公鑰解密(私鑰加密的內容通過公鑰可以解密出來)
 * @param string $public_key 公鑰
 * @param string $data 私鑰加密后的字符串
 * @return string $decrypted 返回解密后的字符串
 * @author mosishu
 */
function publicDecrypt($public_key,$data){
 $decrypted = '';
 $pu_key = openssl_pkey_get_public($public_key);//這個函數可用來判斷公鑰是否是可用的
 $plainData = str_split(base64_decode($data), 128);//生成密鑰位數 1024 bit key
 foreach($plainData as $chunk){
  $str = '';
  $decryptionOk = openssl_public_decrypt($chunk,$str,$pu_key);//公鑰解密
  if($decryptionOk === false){
   return false;
  }
  $decrypted .= $str;
 }
 return $decrypted;
}

//RSA公鑰加密
function publicEncrypt($public_key,$data){
 $encrypted = '';
 $pu_key = openssl_pkey_get_public($public_key);
 $plainData = str_split($data, 100);
 foreach($plainData as $chunk){
  $partialEncrypted = '';
  $encryptionOk = openssl_public_encrypt($chunk,$partialEncrypted,$pu_key);//公鑰加密
  if($encryptionOk === false){
   return false;
  }
  $encrypted .= $partialEncrypted;
 }
 $encrypted = base64_encode($encrypted);
 return $encrypted;
}

//RSA私鑰解密
function privateDecrypt($private_key,$data){
 $decrypted = '';
 $pi_key = openssl_pkey_get_private($private_key);
 $plainData = str_split(base64_decode($data), 128); 
 foreach($plainData as $chunk){
  $str = '';
  $decryptionOk = openssl_private_decrypt($chunk,$str,$pi_key);//私鑰解密
  if($decryptionOk === false){
   return false;
  }
  $decrypted .= $str;
 }
 return $decrypted;
}