Hello! I am pretty good on making web applications and I know how to transfer data to and from client/server, etc. I need some help though learning how to make the data exchanges more secure. That is the reason why I feel kind of scared to publish any web app I make. I wanted to know what are some good guides to help you understand and learn how to secure data transfer with your web application? Things like better authentication for example and making better logins.

You can post any suggestion, but just for your information, I mainly code my web apps with Javascript and PHP. Also, I transfer my data using JSON or XML.

Thanks a lot