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rrinc
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Joined: 24 Feb 2006
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Location: Arkansas, USA
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 Posted: Thu Apr 24, 2008 4:41 am Post subject: Does SSL affect bandwidth? How much? |
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I'm running my site with a 1024bit RSA key (I assume the key length would matter in this case). Obviously everyone wants to have a fast website. I don't handle transactions or terribly sensitive data or anything so I wouldn't mind going to say a 512bit key to add some speed. How much does SSL affect the transfer size? I would assume SSL would add overhead. I'm guessing its insignificant, but I'm still curious.
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aprelium
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Joined: 22 Mar 2002
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| Posted: Thu Apr 24, 2008 1:38 pm Post subject: Re: Does SSL affect bandwidth? How much? |
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| rrinc wrote: | | I'm running my site with a 1024bit RSA key (I assume the key length would matter in this case). Obviously everyone wants to have a fast website. I don't handle transactions or terribly sensitive data or anything so I wouldn't mind going to say a 512bit key to add some speed. How much does SSL affect the transfer size? I would assume SSL would add overhead. I'm guessing its insignificant, but I'm still curious. |
The certificate/key exchange/negiciation occurs only when the connection is established. After that, there is almost overhead since data is encrypted using a 1 to 1 scheme and is sent inside packets with ~ 80 bytes of extra information.
The initial exchange is not even mandatory if the client and the server have already communicated. Servers usually maintain a cache of the result of negociations with clients and will reuse that information for subsequent connections with them. This speeds up the process a lot.
For the gory details, we recommend reading http://en.wikipedia.org/wiki/Transport_Layer_Security#How_it_works .
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jscjso
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Joined: 27 May 2008
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| Posted: Wed May 28, 2008 12:01 am Post subject: |
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| Are we saying https and http have no speed difference after the initial client/server negotiation? |
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rrinc
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Joined: 24 Feb 2006
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| Posted: Wed May 28, 2008 3:46 am Post subject: |
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Yes, except for a very small performance hit to HTTPS which is extremely negligible.
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jscjso
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Joined: 27 May 2008
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| Posted: Wed May 28, 2008 3:51 am Post subject: |
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Rrinc,
Thanks.
My next question will then be why not everyone use https and abandon http?
If speed is not an issue, What is the penalty to use https? Do some browsers having more difficulty to view https?
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olly86
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Joined: 25 Apr 2003
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Location: Wiltshire, UK
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| Posted: Wed May 28, 2008 11:18 am Post subject: |
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Many browsers are configured not to cache any content set across a https connection. Also, if a certificate is not signed by a recognised certification authority many users will not proceed after the warning.
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