This article will explain the TLS protocol through the actual communication data packets, as a section in my column "Computer Network Protocol Quick Start Tutorial".
Since the TLS protocol is not detailed in the old version of the classic data TCP/IP Volume 1, many students are not so familiar with the protocol. However, as one of the most important protocols on the Internet today, basically all mainstream websites have already used TLS encryption, so it is necessary to have a deep understanding of the protocol. The most authoritative reference for TLS must be standard documents such as rfc5246 , but that is for protocol developers. Most people don't look at the daunting RFC when they learn the protocol. This article will help you quickly understand the protocol through the actual communication data packets.
History of TLS
TLS was originally named SSL, SSL1.0 was not released, and the protocol was released as SSL2.0 at the beginning, but this version of the protocol has serious vulnerability risks and is rarely used. The subsequent version evolutions are SSL3.0, TLS1.0, TLS1.1, TLS1.2, TLS1.3. Currently, TLS1.2 is the most widely used. Although SSL3.0 has also been exposed to have some vulnerability risks, it is still possible to use this protocol in old systems that lack maintenance. TLS1.3 is the latest generation of encryption protocol, and currently there is no large-scale application. Figure 1 is a schematic diagram of the position of the TLS protocol in the entire TCP/IP protocol stack, quoted from Microsoft's official description, here :