依赖于OpenSSL扩展

/*加密解密*/
function authcode($string, $operation = 'E') {
  $ssl_public = file_get_contents(DATA_PATH."/conf/cert_public.key");
  $ssl_private = file_get_contents(DATA_PATH."/conf/cert_private.pem");
  $pi_key = openssl_pkey_get_private($ssl_private);//这个函数可用来判断私钥是否是可用的，可用返回资源id Resource id
  $pu_key = openssl_pkey_get_public($ssl_public);//这个函数可用来判断公钥是否是可用的
  if(false == ($pi_key || $pu_key)) return '证书错误';
  $data = "";
  if($operation=='D'){
    openssl_private_decrypt(base64_decode($string),$data,$pi_key);//私钥解密
  }else{
    openssl_public_encrypt($string,$data,$pu_key);//公钥加密
    $data = base64_encode($data);
  }
  return $data;
}
/*生成证书*/
function exportOpenSSLFile(){
  $config = array(
    "digest_alg"    => "sha512",
    "private_key_bits" => 4096,           //字节数  512 1024 2048  4096 等
    "private_key_type" => OPENSSL_KEYTYPE_RSA,   //加密类型
  );
  $res = openssl_pkey_new($config);
  if($res == false) return false;
  openssl_pkey_export($res, $private_key);
  $public_key = openssl_pkey_get_details($res);
  $public_key = $public_key["key"];
  file_put_contents(DATA_PATH."/conf/cert_public.key",$public_key);
  file_put_contents(DATA_PATH."/conf/cert_private.pem",$private_key);
  openssl_free_key($res);
}

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