An aggressive policy to remove SSL/TLS certificates signed with the SHA-1 hashing algorithm was announced in November 2013 by Microsoft. The SHA-1 hashing algorithm is was considered weak to collision attacks, so the goal was to move to the stronger SHA-2 family of hashing algorithms.

The hash is a cryptographic representation of the certificate, which is used in certificate validation. It should be hard to have a hash collision where two certificates have the same hash. As SHA-1 is weak, the SSL/TLS industry now signs certificates mostly with the SHA-256 version.

style="font-size: 14pt;">SHA-1 Deprecation Program

The SHA-1 deprecation program required that certification authorities (CAs) stop signing with SHA-1 as of January 1, 2016. The goal would then have Windows stop trusting SHA-1 signed SSL/TLS certificates in 2017. Apple, Google and Mozilla all support the deprecation plan.

The good news is the certificate subscribers have been very efficient at upgrading to SHA-2 signed certificates. Recent data from Netcraft shows that about only 2.5-percent of certificates found in their monthly SSL survey are signed with the SHA-1 hash.


Netcraft SSL Survey – November 2016

Other surveys indicate the percentage may be quite a bit higher. Please note that the certificate subscribers have been focusing their energy on upgrading the publicly trusted certificates that are used by browsers. In other use cases, the certificate may be implemented in a server-to-server mode or may be issued from a private trust CA, which is not impacted by the SHA-1 deprecation plan. Also note that some subscribers have picked a certificate expiry date of December 31, 2016, so we anticipate a large move to SHA-2 in late December.

When will Browser Users be Impacted?

It is anticipated that all popular browser will show errors for SHA-1 signed SSL/TLS certificates in 2017:

  • Chrome: Google indicates Chrome 56 to be released at the end of January 2017 will remove trust for SHA-1 certificates from publicly trusted CAs. With Chrome 57, trust will be removed for SHA-1 certificates issued from private trust CAs. For private or local CAs, an enterprise can correct this error by implementing a change to enable SHA-1 for local anchors.
  • Firefox: Mozilla announced that with release 51 in January 2017, Firefox will show an Untrusted Connection error if a SHA-1 certificate chains to a root in the Mozilla CA certificate program that users can override.
  • Internet Explorer and Edge: Microsoft stated that on February 14, 2017 an update to Microsoft Edge and Internet Explorer 11 will be released to display an Invalid Certificate warning page alerting users that their connection is not secure. Although not recommended, browser users will have the option to continue to the website.
  • Safari: Apple has not stated a SHA-1 policy, but it is expected that browsers running on OS X or iOS will stop supporting SHA-1 signed certificates in 2017.

Certificate subscribers should keep moving to SHA-2 to ensure website visitors will not encounter browser error messages when using their website.

If you have yet to migrate to SHA-2, check out Entrust Datacard’s SHA-2 Migration Guide. It will help you plan and execute a successful SHA-2 migration to avoid extra costs, eliminate service disruptions and ensure compliance.

Bruce Morton

Bruce Morton

Bruce Morton is a pioneering figure in the PKI and digital certificate industry. He currently serves as Director for Certificate Services at Entrust Datacard, where he has been employed since 1999. His day-to-day responsibilities include managing standards implementations, overseeing Entrust Datacard’s policy authority, and monitoring Entrust Certificate Service for industry compliance.