Victor Du
Jumping in late, but the idea that *TCP* (and not TLS protocol design)
adds round-trips to SSL warrants some evidence (it is very temping to
express this skepticism more bluntly).

With unextended SMTP for example, the minimum RTT count is:

        0. SYN  SYN-ACK
        1. ACK  220
        2. HELO 250
        3. MAIL 250
        4. RCPT 250
        ... n recipients
           RCPT 250
        4+n DATA 354
        5+n ... stream of message content segments<CRLF.CRLF>

so it takes at least 6 RTTs to perform a delivery (of a short
single-recipient message), but only 1 of the 6 RTTs is TCP
"overhead". This is improved with PIPELINING:

        0. SYN                          SYN-ACK
        1. ACK                          220
        2. EHLO                         250 ... PIPELINING ...
        3. MAIL RCPT(n times) DATA      250 250 (n times) 354
        4. ... stream of message content segments<CRLF.CRLF>
re: Dutch Transport Card Broken Dutch Transport Card Broken Fixing SSL (was Re: Dutch Transport Card Broken)

TCP requires minimum of seven message exchange for reliable transport
.... VMTP (rfc 1045) got that down to minimum of five messages, and XTP then
got it down to three messages minimum for reliable transport (disclaimer
we were on the XTP technical advisory board).

i've frequently pontificated that with reliable registration of public keys
in the dns system and then piggy-backing any registered public key in
standard DNS response .... then it would be possible to encode the
randomly generated secret key (with that public key) and the encrypted
message in the XTP packet for minimum 3 packet exchange.

http already went thru its period of problems of implicit assumptions
with tcp. tcp sessions were assumed to be long lived and session shutdown
was assumed to be relatively infrequently. non-session activity like http
was always assumed to use udp for efficiency. the http ignored all of
that and used tcp for non-session activity. as a result, webserver systems
went thru a period where the processors was spending 95+ percent of
processor in the session shutdown processing. systems then were retrofited
with new kind of tcp session shutdown implementation to handle the
misuse by http.

the original ssl deployment was to 1) encrypt data in transit and
2) authenticate the server. the implicit assumption was that the
user understood the binding between the business and the url.
the browser then provided the second part, verifying the binding
between the url and the server contacted (was the server that
the user thot they were talking to, the server they were actually
talking to).

The dependency for valid ssl operation was violated almost
immediately when merchants found that ssl overhead reduced thru
thruput by 5-10 times. the regression was instead of initial contact
of the webserver (presumably url supplied by user) being ssl,
ssl was moved to checkout/pay phase where the user clicked
on a button (and url) provided by the webserver (not a url
provided by the user). It was no longer possible to provide
any assurances as to the authentity of the webserver contacted
(ssl purely being reduced to encrypting data in transmission).

we had been called in to consult with the small client/server
company on using this technology (they created) called SSL
for payment transactions

and had to go thru detailed walk thrus of the technology as
it applied to actual business processes (and the associated
implicit dependencies) ... as well as detailed walk thrus of the
new business operations that were calling themselves
certification authorities.

the other issue that we came up in applying this SSL technology
was communication between webservers and something called
the payment gateway. for  this communication we mandated mutual
authentication ... this was before mutual authentication had
been implemented in SSL. It turns out that by the time
we had it all implemented and deployed ... it also became
very apparent that the things called digital certificates
were redundant and superfluous.

the basic design point for digital certificates is first time
communication between total strangers. the payment gateway
business processes required that all the merchants had
to be pre-registered with the payment gateway and the payment
gateway pre-registered with all the merchants .... violating the
basic justification for having digital certificates.

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