Tag Archives: UX

Positive Trust Indicators and SSL

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[Full disclosure I work at Google, I do not speak for the Chrome team, and more generically am not speaking for my employer in this or any of my posts here]

Recently Melih did a blog post on the topic of browser trust indicators. In this post he makes the argument that DV certificates should not receive any positive indicator in the browser user interface.

I agree with him, just not for the same reasons. Positive trust indicators largely do not work and usability studies prove that is true. Browsers introduced the “lock” user interface indicator as part of a set of incentives and initiatives intending to encourage site operators to adopt SSL.

What is important is that these efforts to encrypt the web are actually working, over half the web is now encrypted and more importantly the adoption rate is demonstrating hockey stick growth.

As a result, in 2014 Chrome started down the path of deprecating positive trust indicators all together. In-fact today Chrome already marks HTTP pages as “Not secure” if they have password or credit card fields.

The eventual goal being able to mark all HTTP pages as insecure but for this to happen SSL adoption needs to be much higher, I suspect browsers will want to see adoption in the 90% to 95% range before they are willing to make this change.

This is relevant in this case because if all pages are encrypted what value does a positive trust indicator have? None. This means that when all HTTP pages get marked “Not secure” we will probably see the lock icon disappear.

So, as I said, I agree with Mehli, the “Secure” indicator should go away but so should the lock, the question is not if, but when.

But what does that mean for EV trust indicators? I am a member of a small group, a group that thinks that EV certificates can provide value. With that said today EV certificates have some major shortcomings wich significantly limit their value, some of which include:

  • It is not possible to get an EV wildcard certificate,
  • CAs, largely, have ignored automation for EV certificates,
  • Due to the lack of automation EV certificates are long lived and their keys more susceptible to theft as a result,
  • The vetting processes used in the issuance of EV certificates are largely manual making them expensive and impractical to use in many cases,
  • CAs market them as an antiphishing tool when there are no credible studies that support that,
  • The business name in the certificate is based on the legal name of the entity, not the name they do business under (DBA),
  • The business address details in the certificate are based on where business is registered (e.g. Delaware),
  • There is no contact information in the certificate, short of the taxation address, that a user can use to reach someone in case of an issue.

Addressing these issues have either been actively been resisted by CAs, for example, DigiCert has tried to get EV wildcard certificates to be a thing in the CA/Browser Forum a number of times but CAs have voted against it every time, or simply ignored.

There are some people who are working towards addressing these gaps, for example, the folks over at CertSimple but without CAs taking a leading role in redefining the EV certificate the whole body of issues can nott be resolved. Importantly until that happens you won’t see browsers even considering updates to the EV UI.

Given this reality, browsers have slowly been minimizing the details shown in EV certificates since they can give users the wrong impression and have limited value given the contents of the certificate.

It is my belief that unless the CAs work together to address the above systematic issues in EV certificates that minimization will continue and when the web is “encrypted” it won’t just be DV that loses its positive trust indicator, it will be EV also.

 

Why might you have a certificate with a SHA1 based signature in its chain that is valid beyond 2016/1/1?

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NOTE: Google has updated the plan they will be using to deprecate SHA1 based certificates. The content in this post is still mostly accurate but for dates please see the thread. Personally I think the new plan is a good one. The upsides in this post are still accurate and it is my hope people switch to SHA256 based certificates as quickly as possible.

So there is a plan under discussion to “degrade” the user experience for SSL sessions protected with certificates (or chains) that contain a SHA1 based signature that are valid beyond 2016/1/1.

This 2016/1/1 date was apparently discussed at a CAB Forum meeting six months ago, prior to that the “sunset date” for SHA2 was considered to be 2017/1/1.

Given Chrome represents such a large percentage of the browser ecosystem and they appear to be unwaveringly marching towards this new date I think its fair to refer to this date as the “new sunset date”.

There have been lots of conversations about this topic from the perspective of a CA and that of a browser but not so much from a perspective of a certificate holder.

There are a few cases why you might have such a certificate:

  1. Your certificate was issued before the new sunset date was specified.
  2. When the new sunset date was specified your certificate authority did not update their system to restrict use of that algorithm to expire by that new date.
  3. Your certificate authority gave you the option of choosing which signature suite (and hash algorithm) and expiration dates to use and you chose SHA1.

Some might ask why CAs did not simply stop issuing certificates that utilize SHA1 based signatures all together when Microsoft issued their goal to deprecate by 2017. The answer to this is simple; there is a large number of XP machines out there (15% of the Internet and over 35% of browsers in China) and its unclear how many of them have Service Pack 3 which is necessary to support certificates with SHA2. There are also concerns about the number of mobile and embedded devices that also do not support SHA2.

So how big of a risk is the interoperability impact? It’s hard to say; some numbers i have seen suggest it is less than 1% of traffic but honestly it doesn’t appear possible to measure  the number of XP machines without SP3 and if it were it still wouldn’t take into consideration the devices that do not support SHA2 and we know such devices were shipping as recently as two years ago.

So that takes me to the main reason for this post; it’s my guess that the primary reason you have a certificate that will be effected by this change is that the CAs honestly did not realize google was moving the sunset date forward and were adopting migration plans that they felt balanced interoperability, usability and security.

With that said I believe google sincerely feels this change is in the best interest of the internet and that the user interface changes they are proposing are subtle enough that it wont be noticed by most (see : A Large-Scale Field Study of Browser Security Warning Effectiveness [pdf]).

Unfortunately this leaves you the server administrator stuck somewhat in the middle. You will have to choose to give up views and revenue from these clients that do not support SHA2 or all of your users who use Chrome will see a degraded user experience.

What will Chrome’s SHA1 early warning look like?

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NOTE: Google has since revised its plan to enable a more gradual migration to SHA256, this post is no longer accurate.

For the last few weeks there has been an ongoing discussion on the Chromium security-dev mailing list on how Google intends to implement a user interface change to warn users that a SHA1 certificate is in use.

I wont talk to the reasoning behind this change or to the current and future security properties of SHA1 in this post but I thought some folks might be interested in what this might ultimately look like. I say might because right now there is only a mail thread and who knows how things will evolve and what the copy would be in such user interfaces.

With that said the thread does describe what affordances they intend to use when a site has a certificate where it or the corresponding certificate chain has SHA1 based signature in it (excluding the root) that expires after 2016/1/1 the user interface may be “degraded” for these sessions.

At this time it seems the “red x” that is used for mixed content will be used; if so this will look something like this:

 1

 

 

 

 

For the SHA1 certificates that expire after 2017/1/1 if that page contains active content such as JavaScript and CSS that is served over a SSL session with such a certificate they will not be loaded unless the user explicitly chooses to approve their execution, this would look something like this:

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Again for SHA1 certificates that expire after 2017/1/1 if the page contains passive content (such as images) that is served over a SSL session with such a certificate it will not be loaded unless the user chooses to do so and the lock will get a yellow arrow, which will look something like this:

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Which combinations of these things one will see would be dependent on the specific combination of conditions but this will give you some idea on what these changes may look like.

Ryan