Add support for SRTP (#1977)

The goal is to have Zoom flows classified as "Encrypted" and not as
"Cleartext".

Start documenting the list of protocols supported by nDPI;
format, verbosity and content are still a work-in-progress.

1 files changed, 19 insertions, 0 deletions

diff --git a/doc/protocols.rst b/doc/protocols.rst
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+nDPI Protocols List
+####################
+
+This page provides the list of the protocols/applications supported by nDPI. For each protocol there is a brief description, some links to further, more detailed information and, optionally, some notes that might be useful when handling such a protocol (from the application/integrator point of view)
+
+Work in progress!
+
+.. _Proto 338:
+
+`NDPI_PROTOCOL_SRTP`: SRTP (Secure Real-time Transport Protocol)
+==============================================================
+The Secure Real-time Transport Protocol (SRTP) is a profile for Real-time Transport Protocol (RTP) intended to provide encryption, message authentication, integrity, and replay attack protection to the RTP data.
+
+References: `RFC3711 <https://datatracker.ietf.org/doc/html/rfc3711>`_.
+
+Notes:
+
+- You can think of SRTP simply as the "encrypted" version of RTP, something like HTTPS vs HTTP;
+- It is not usually possible to tell RTP from SRTP. nDPI generally uses the former and it uses the latter only when it is really sure that the media stream has been encrypted.