跨服务器的通信必须确保安全。

The communication across the servers has to be secured.

youdao

至于跨域的限制，跨文档进行消息传输的API非常有趣的允许跨源(cross - origin)通信，但是开发者需要非常小心的使用它，在任何时候确保安全性。

About cross-domain limitation, the cross Document Messaging API is interesting to allow cross-origin communication but the developer as to be very careful using it and ensure security at all time.

youdao

GnuPG是GNU用于确保安全通信和数据存储的工具。

GnuPG is GNU's tool for secure communication and data storage.

youdao