Don't design security protocols (Was: Gemini privacy

Stephane Bortzmeyer stephane at
Wed Mar 10 08:39:56 GMT 2021

On Tue, Mar 09, 2021 at 07:36:37PM +0100,
 nothien at <nothien at> wrote 
 a message of 41 lines which said:

> I've been collecting ideas for a new transport security protocol.  I
> know ~spc's stance on crypto ("get it approved by the crypto
> community, make an implementation, then we'll talk"), and I'm not
> saying we should switch to a magic protocol that doesn't exist; but
> that we should at least consider making a wishlist of sorts of all
> the things that we would want out of a "good" transport security
> protocol (if you have any such ideas, please share them with me).

There are two kinds of people who design security protocols: geniuses
(who don't need my advice) and people who overstimate their abilities.

Seriously, designing a secure transport protocol is *hard*. I repeat,
HARD. There are are many traps. One of the most important is that
failures are not obvious. If you create a program to display images,
anyone, even not an expert, can see if the program works or not. If
you create a security protocol, even experts may not be able to tell
immediately that there is a vulnerability.

And I don't even mention implementation, which adds its own risks.

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