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I was wondering, does encryption used over the Internet in a web browser noticeably slow down the speed of data transfer? I keep reading about stuff like HTTPS, but I always wonder if there's a speed disadvantage in securing your data over HTTPS, encrypted instant messages, or even an encrypted LAN VNC connection.

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up vote 2 down vote accepted

Generally any encryption or decryption process takes longer than clear messages;but if that encryption approach is supported by source and destination over network we can say it takes less time to proceed.

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Thanks for the info, but I am specifically curious about just how much of a difference it makes. I don't need to know the technical aspects of it, I just want to know how much slower it would be for simple encrypted web browsing. For example, if I use standard HTTPS with Gmail, would requests be several times as slow? A fraction as slow? 50% slower? Barely slower at all? – Nicolas McCurdy Aug 8 '10 at 23:13
    
of course it s not 50% but lets say 10-15% i m saying by experience,but at least you could be sure your data is less under sniffing or revealing. – user44509 Aug 8 '10 at 23:23
    
Thanks, this is helpful. :) – Nicolas McCurdy Aug 8 '10 at 23:35

It is a question of rates. If your CPU can encrypt data at 30MB/s, but you can only transfer data at 10MB/s, then encrypted communication will only be slow relative to unencrypted communication if there is something else hogging the CPU and bringing the encryption rate below 10MB/s.

If there is something else restricting the transfer rate (say the time it takes to read from disk the data being encrypted and then transferred), then that also could be a limiting factor, but would not be due to encryption.

Other than that, there is only latency to worry about, and I think most implementations are reasonably well tuned to reduce the impact of encryption on latency.

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With todays fast PCs I don't think encryption itself will slow the speed of transfer.

However, general web browsing over a secure (HTTPS) connection can be slower because the browser is less likely to cache secure pages, and so there are more requests to the server.

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