Google encourages the Certification Authorities to accelerate SHA-2 transition

Google encourages the Certification Authorities to accelerate SHA-2 transition

Following Google's announcement in early September regarding the transition to SHA-2, we wanted to remind you of the significance of this migration, and the implications of this decision made by Google.

A brief reminder:

  • The SHA-1 algorithm is still considered a reliable hash. However, some experts see it as “potentially weak over the long term”.
  • The longer a hashing algorithm is, the harder it is to detect collisions (see this blog post to look at hash algorithm in more detail). This explains the reasoning behind the transition: SHA-2 is a similar algorithm but produces a longer fingerprint.
  • Microsoft, a member of the CA/Browser forum, initiated the transition to SHA-2 by announcing in November 2013 that no SSL certificate using SHA-1 would be recognised by its operating system from 1st January 2017. Microsoft also urged Certification Authorities (CA's) not to issue or reissue any SHA-1 certificate from 1st January 2016.

It seems that Google's announcement on the deprecation of SHA-1 in Chrome is causing a lot of controversy. Not only has the giant of the net imposed its own law on a topic usually occupied by Microsoft, but the announcement is also undermining the power of the Certification Authorities.

Why does Google have any input concerning this subject?

Thanks to Chrome, Google is an established entity in the web browser market (Chrome is used by 60% of web users worldwide). Web browsers are responsible for checking the validity of SSL certificates, so Google has a prominent place in discussions on this topic.

What is Google going to do exactly?

In an open-ended conversation on the 20th August 2014, Google announced it would accelerate the transition to SHA-2 by changing the user experience on websites secured by an SSL certificate expiring after May 2016. The next three versions of Chrome (39, 40 and 41) will gradually begin to appear with visual alerts such as shown below:

These visual alerts will be shown on the URL bar of the browser, and will not require any action to be taken by the user (no pop-up to close, no button to click to gain access to the website etc.).

Why does Google want to speed up the process of ending certificates using SHA-1?

Google believes that the deadline proposed by Microsoft is too long, and it is quite possible to transition to SHA-2 faster. Among the arguments cited for this is the example of the old algorithm MD5 which was made obsolete but remained used for a long time. According to Google, this demonstrates the significance of quickly ending SHA-1 before it is compromised.

Such a modification of the user experience on Chrome does not call into question the role of Certification Authorities, but it divides the SSL industry on the issue of timings imposed by Google: is it reasonable for Google to announce a deadline so short, compared to the deadline of Microsoft’s? While the debate continues, the facts are clear: from the first quarter of 2015, 60% of Internet users will see a red lock on the URL of a website using an SSL certificate with SHA-1, expiring after 1st January 2017.

Is my certificate SHA-1 ?

Must we reissue the certificate in SHA-2 immediately then?

Our answer is yes. We do not want to encourage panic, followed with massive reissues (which was the case during the announcement of the Heartbleed bug), but the firmness of Google on the subject does make us reconsider 2017 as the deadline for SHA -1.

It would be unwise to postpone the reissue of a SHA-2 certificate as switching is going to be a quick uncomplicated process. You can reissue your certificate in SHA-2 at any time and at no cost with SSL247®. By doing so you will avoid the panic of reissue at the last minute, and you can detect possible incompatibilities with your hardware or applications before it causes any issues. These incompatibilities are few, but they exist (you can download our PDF file on SHA-2 with the list of compatible applications and operating systems,) and it has often been an argument used in debates regarding this subject.

Windows XP SP2 and earlier versions are indeed not compatible with SHA-2.

It seems impossible right now to tell whether having Windows XP users unable to launch a secure connection to your server may not be a significant risk; statistics about the exact current share of Windows XP users varies from one expert to another.

If you are worried that some of your users are still using these versions of Windows XP, let's be clear: these users risk more than just a problem of incompatibility with SHA-2. Remember that Windows XP was launched in 2001 and replaced by Windows Vista in 2007, and that Microsoft has stopped all Windows XP support over 6 months ago. Any individual or organisation still using an earlier version of Windows XP SP3 does so for a specific reason (because they use applications compatible only with XP for example), and probably do not want to update their operating system.

We believe that individuals or organisations still using Windows XP are aware of and accept the risks associated with using it. Also worth noting is that there is a patch for Windows XP and Windows Server 2003 enabling it to support SHA-2.

Have a question? A comment? Contact our accredited web security experts now on 0203 143 4120 (London office) or

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Posted on Monday 06 October 2014 by Hannah Smith

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