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Why is HTTP still commonly used, instead what I would believe much more secure HTTPS?

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6 Answers

up vote 40 down vote accepted

SSL/TLS has a slight overhead. When Google switch Gmail to HTTPS (from an optional feature to the default setting), they found out that CPU overhead was about +1%, and network overhead +2%; see this text for details. However, this is for Gmail, which consists of private, dynamic, non-shared data, and hosted on Google's systems, which are accessible from everywhere with very low latency. The main effects of HTTPS, as compared to HTTP, are:

  • Connection initiation requires some extra network roundtrips. Since such connections are "kept alive" and reused whenever possible, this extra latency is negligible when a given site is used with repeated interactions (as is typical with Gmail); systems which serve mostly static contents may find the network overhead to be non-negligible.

  • Proxy servers cannot cache pages served with HTTPS (since they do not even see those pages). There again, there is nothing static to cache with Gmail, but this is a very specific context. ISPs are extremely fond of caching since network bandwidth is their lifeforce.

  • HTTPS is HTTP within SSL/TLS. During the TLS handshake, the server shows its certificate, which must designate the intended server name -- and this occurs before the HTTP request itself is sent to the server. This prevents virtual hosting, unless a TLS extension known as Server Name Indication is used; this requires support from the client. In particular, Internet Explorer does not support Server Name Indication on Windows XP (IE 7.0 and later support it, but only on Vista and Win7). Given the current market share of desktop systems using WinXP, one cannot assume that "everybody" supports Server Name Indication. Instead, HTTPS servers must use one IP per server name; the current status of IPv6 deployment and IPv4 address shortage make this a problem.

  • HTTPS is "more secure" than HTTP in the following sense: the data is authenticated as coming from a named server, and the transfer is confidential with regards to whoever may eavesdrop on the line. This is a security model which does not make sense in many situations: for instance, when you look at a video from Youtube, you do not really care about whether the video really comes from youtube.com or from some hacker who (courteously) sends you the video you wish to see; and that video is public data anyway, so confidentiality is of low relevance here. Also, authentication is only done relatively to the server's certificate, which comes from a Certification Authority that the client browser knows of. Certificates are not free, since the point of certificates is that they involve physical identification of the certificate owner by the CA (I am not telling that commercial CA price their certificates fairly; but even the fairest of CA, operated by the Buddha himself, would still have to charge a fee for a certificate). Commercial CA would just love HTTPS to be "the default". Moreover, it is not clear whether the PKI model embodied by the X.509 certificates is really what is needed "by default" for the Internet at large (in particular when it comes to relationships between certificates and the DNS -- some argue that a server certificate should be issued by the registrar when the domain is created).

  • In many enterprise networks, HTTPS means that the data cannot be seen by eavesdroppers, and that category includes all kinds of content filters and antivirus software. Making HTTPS the default would make many system administrators very unhappy.

All of these are reasons why HTTPS is not necessarily a good idea as default protocol for the Web. However, they are not the reason why HTTPS is not, currently, the default protocol for the Web; HTTPS is not the default simply because HTTP was there first.

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+1 for static content takes a hit. Consider a site with multiple <img> tags. Since each image will have a separate connection, the computational overhead of say a 2048-bit or 4096-bit encrypted connection can become fairly significant on mobile platforms where increasesd CPU usage quickly drains a battery, users might avoid your site because for one reason or another they think it drains their battery. This is of course one merit to hosting non-confidential static content on a separate server (without SSL). –  Puddingfox Jun 6 '11 at 1:17
    
+1 @puddingfox: Interesting point regarding the CPU overhead to mobile devices. –  blunders Jun 6 '11 at 2:02
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@puddingfox: I used to work as a PM for mobile development, and as I see it, if security is required then the current favorite is to use a platform-specific native app, which uses a encrypted compressed data-only REST/SOAP API to talk to the web service. The SSL setup use fx 2048-bit (remember, after setup you will switch to fx 128 bit AES), but CPU load for encryption is not a real problem. The real problems with in-browser apps/SSL are network latency, and buggy Javascript support on mobile browsers. That's why native apps are preferred. –  Jesper Mortensen Jun 6 '11 at 7:19
    
"slight" overhead? I think not. Latency is the killer for web based applications. This is made worse by the history of problems on MSIE's ssl implementation (now mostly resolved). There are also additional costs related to SSL (buying a cert is just the start). –  symcbean Jun 6 '11 at 9:28
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@puddingfox: a browser will open only a few SSL connections to a given site (e.g. 3 or 4), using HTTP keep-alive to send several successive HTTP requests within each. Moreover, only the very first one needs asymmetric key exchange (the one where a 2048-bits-or-so key is involved); the other connections will use the SSL/TLS "resume session" feature (faster handshake, less messages, symmetric crypto only). Finally, most SSL/TLS server use a RSA key and the client part of RSA is cheap (the server incurs most of the cost in RSA). –  Thomas Pornin Jun 6 '11 at 10:58
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While there are great answers already given, I believe that one aspect is overlooked so far.

Here it is: Plain HTTP is the default protocol for the web because the majority of information on the web doesn't need security.

I don't mean to belittle the question, or the security concerns of some web sites/applications. But we can at times forget how much web traffic:

  • contains only completely public information
  • or has little or no value
  • or where having more visitors is seen as increasing the value of the site (news media, network effect sites)

A few quick examples, I'm sure you can quickly make more in your mind:

  • Almost all company websites, sometimes called "brochure-ware sites", listing public information about a company.
  • Almost all of the news media, blogs, TV stations, etc that have chosen advertisement support as their primary monetization strategy.
  • Services which may offer logins and additional personalization, but who also give away their content for free to anyone browsing anonymously (YouTube fx).
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I agree, there's no reason to leave anything overlooked. One thing I've wondered, and relates to your point on public information. Are URLs viewed during HTTPS transactions to one or more websites from a single IP distinguishable? For example, say the following are HTTPS URLs to two websites by one IP over 5 mins: "A.com/1", "A.com/2", "A.com/3", "B.com/1", "B.com/2"; would monitoring of packets reveal nothing, reveal only the IP had visited "A.com" and "B.com", reveal a complete list of all HTTPS URLs visited, only reveal IP's of "A.com" and "B.com", or something else? –  blunders Jun 6 '11 at 0:15
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@blunders: Comments aren't the best places to ask new questions. Have a look at the following link, or open a new question. security.stackexchange.com/questions/2914/… –  Jesper Mortensen Jun 6 '11 at 10:36
    
+1 @Jesper Mortensen: Thanks, agree. Reviewed the other question, and posted this question: Are URLs viewed during HTTPS transactions to one or more websites from a single IP distinguishable? –  blunders Jun 6 '11 at 12:23
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  • It puts significantly more CPU load on the server, especially for static content.
  • It's harder to debug with packet captures
  • It doesn't support name-based virtual servers
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If the packet captures are non-malicious why would the debugger not have access to the keys? If that's not the source of the issue, then what is? –  blunders Jun 5 '11 at 19:22
    
The implementation of SSL-enabled name-based virtual servers appears possible, is this wrong? –  blunders Jun 5 '11 at 19:24
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@blunders, no, the debugger doesn't have access to the keys, because decryption is done by the application, not by the OS. –  D.W. Jun 6 '11 at 18:15
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@blunders, regarding name-based virtual servers, no, the problem is that SNI is not supported on WinXP. See @Thomas's answer. –  D.W. Jun 6 '11 at 18:16
    
+2 @D.W.: Guess it makes sense that it'd be hard to have a universal method for sharing application specific implementations; meaning you couldn't just make a copy of the keys and the configs to render the decryption built into the debugger. And yes, I'd seen that listed in @Thomas answer, which was posted after @Mike Scott; left it as is, since I'd wondered if @Mike Scott had another reason. Cheers! –  blunders Jun 6 '11 at 18:47
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Http was always the default. Initially https was not needed for anything, it was pretty much an addition tacked on as it became obvious security was needed in some circumstances.

Even now, there are so many web sites which do not need https that it is still not a convincing argument to replace http entirely.

With ever more effective mechanisms for running TLS secured connections, the CPU overhead is becoming much less of an issue.

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No one has pointed out a clear problem that arises from using http as default, rather than https.

Hardly anyone bothers to write the full uri when requesting a resource that needs to be encrypted and/or signed for various purposes.

Take gmail as an example, when users are visiting gmail.com, they are in fact visiting the default protocol of http, rather than https. At this point security has failed in scenarios where the adversary is intercepting the traffic. Why? Because its possible to strip html from https request, and point them to http.

If https was in fact the default protocol, your sessions to websites would have been protected.

To the question why http is chosen over https, the various answers above applies. The world is just not ready for widespread use of encryption yet.

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Thomas has already written an excellent answer, but I thought I'd offer a couple more reasons why HTTPS is not more widely used...

  • Not needed. As Jesper's answer insightfully points out "the majority of information on the web doesn't need security". However, with the growing amount of tracking taking place by search engines, ad companies, country-level internet filters and other "Big Brother" programs (eg. NSA); it is raising the need for greater privacy measures.

  • Speed. It often feels slow because of the extra round trips and extra requests for certificate revocation lists (OCSP etc.). Thankfully SPDY (created by Google, and now supported in all major browsers), and some interesting work from CloudFlare are helping shift this.

  • Price of certificates. Most certificate authorities charge exhorbitant amounts of money (hundreds of dollars) for a certificate. Thankfully there are free options, but these don't get as much publicity (not sure why?).

  • Price of IP addresses. Until IPv6 becomes widespread, websites will face the rising scarcity (and thus cost) of IPv4 addresses. SNI is making it possible to use multiple certificates on a single IP address, but with no SNI support in Windows XP or IE 6, most sites still need a dedicated IP address to provide SSL.

  • Increase in server CPU usage. This is a common belief, but according to Google "SSL/TLS is not computationally expensive any more".

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