TLS
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... initiating and terminating machines perform a "tuning reset," not
unlike the way starting a TLS negotiation discards cached session
state ...
... BEEP framing. The two endpoint machines may
therefore negotiate TLS between them, passing certificates
appropriate to the endpoints ...
... closes the other.
[4] This greeting may include the TLS profile, allowing initial and
final to communicate without proxy1 understanding or interfering
...
... If a transport security layer (such as TLS) has been negotiated over
the session, the semantics ...
... 538 Encryption already enabled
(E.g., TLS already negotiated, or a SASL that
provides encryption ...
... has been established will prevent intermediate proxies from observing
or modifying the cleartext information exchanged, but only if TLS
certificates are properly configured during the negotiation ...