Siemens SIMATIC ET 200AL, System Manual

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Communications services
3.6 Secure Communication
Communication
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Function Manual, 05/2021, A5E03735815-AJ
Secure communication with STEP 7
STEP 7 as of V14 provides the required PKI for the configuration and operation of secure
communication.
Examples:
•
The Hypertext Transfer Protokoll (HTTP) turns into Hypertext Transfer Protokoll Secure
(HTTPS) with the help of the TLS (Transport Layer Security) protocol. Since HTTPS is a
combination of HTTP and TLS, it is called "HTTP over TLS" in the corresponding RFC. You
can see in the browser that HTTPS is being used; this is indicated by the URL "https://"
instead of "http://" in the address bar of the browser. Most browsers highlight such secure
connections.
• Open User Communication turns into secure Open User Communication. The underlying
protocol is also TLS.
• E-mail providers also offer access over the "Secure SMTP over TLS" protocol to increase the
security of e-mail communication.
The figure below shows the TLS protocol in the context of communication layers.
Figure 3-6 TLS protocol in the context of communication layers
Secure communication with OPC UA
An OPC UA server is implemented in S7-1500 CPUs as of firmware V2.0. OPC UA Security also
covers authentication, encryption and data integrity with digital X.509 certificates and also
uses a Public Key Infrastructure (PKI). Depending on the requirements placed by the
application, you can select different security levels for the end point security. The description
of the OPC UA server functionality is covered in a separate section.