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Re: [libmicrohttpd] HTTPS delay

From: Christian Grothoff
Subject: Re: [libmicrohttpd] HTTPS delay
Date: Sun, 30 Oct 2011 18:53:11 +0100
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv: Gecko/20111004 Icedove/3.0.11

On 10/30/2011 06:12 PM, Avner Flesch wrote:
Thanks for the fast reply.
I am using Linux on powerpc 875 (50 MHz).

Then 6s could totally be encryption. This article might be a good start for cipher choices:

Also make sure that you compiled libgcrypt with optimizations (-O3).

Best regards,


-----Original Message-----
From: Christian Grothoff<address@hidden>
Reply-to: libmicrohttpd development and user mailinglist
To: address@hidden
Subject: Re: [libmicrohttpd] HTTPS delay
Date: Sun, 30 Oct 2011 17:56:01 +0100

On 10/30/2011 05:16 PM, Avner Flesch wrote:

I am developing simple secured HTTP (HTTPS) server for embedded system.
It seems that the delay is rather long - for example ~230 KB file delay
is almost 6 seconds.
Is there a way to speed it up?

On an embedded system, I suspect the main contributor to latency is CPU
time for the cryptographic operations (you didn't say what kind of
embedded system, so it's hard for me to say if 6s is good or bad).

You could configure MHD to use different (faster) ciphers, which may
give you significant performance improvements (if CPU speed is the
problem). Google's choices for HTTPS might be a good starting point.

Changing the default cipher suite in MHD is done using
MHD_OPTION_HTTPS_PRIORITIES followed by a string specifying the ciphers
(see 'gnutls_priority_init' documentation for the format of that string).

Other than that, there is little you can do: HTTPS is slow, and I'm
generally pretty sure that MHD and GNUtls are about as fast as they can
be (so switching to a different HTTP(S) server would also most likely
not help you --- unless that server uses a different cipher suite by
default, and in that case you could just use the option I gave above).

Happy hacking!


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