Browsers impose transition to SHA-2

14 January 2016

Google Chrome has announced that it will stop supporting the hashing algorithm SHA-1. SHA-2 is the follow-up to SHA-1 and set to become the new standard, since SHA-1 certificates are no longer considered to be secure. Google, Microsoft and Mozilla want to block SHA-1 from January 2017 at the latest, although they are considering moving this date up to July of 2016 because of the increasing security risks.

The different variants of SHA are, like the older MD5, hash codes with which a summary of a certificate is calculated. This is then digitally signed by a CA. A visitor can use this to verify the authenticity of the certificate.

Browsers warn against SHA-1

Starting in early 2016, most browsers will display a warning if a user attempts to visit a website with an SHA-1 certificate. Browsers do accept SHA-1 for root certificates, because these are included on the browsers’ trusted lists. Root certificates are issued by Certificate Authorities like Comodo and Symantec. This is still secure, because SHA-1 signatures for root certificates are used for the verification of their identity, not for the verification of the certificates for websites.

Misuse of SHA-1 is relatively cheap

The dangers of SHA-1 certificates have been known for a while now. The browsers hastily searched for a solution to the problem, because various studies revealed that it is relatively cheap for cybercriminals to attack connections protected with SHA-1. A weak hash function makes it possible to create two certificates with the same hash, which allows one to falsify certificates. This enables parties with the right capacity to mimic commonly used websites and intercept traffic to this website.

SHA-2 not supported by older browsers

Per 1 January 2016, SHA-1 certificates may no longer be issued. A downside to this is that not everyone has a system that supports SHA-2 certificates. Windows XP SP2, Android 2.2 and older systems do not support SHA-2, although these systems are still commonly used in large parts of the world. This means that around 37 million people all over the world, but mainly concentrated in developing countries, will encounter issues with their certificates.

Ready for the future

The follow-up SHA-2 and the even newer hashing algorithm SHA-3 will serve us for many years to come, researchers expect. These systems contain fundamental changes and offer more than enough resistance to current forms of attack. As our computers’ computational capacity increases, newer SHA hashing algorithms will continue to be developed in order to safeguard the security of data traffic.

How can I tell if a website uses an SHA-1 certificate?

At the moment, it is not yet possible to easily tell whether a secure website is protected with an SHA-1 or an SHA-2 certificate. Chances are that the website already has an SHA-2 certificate, but it is advisable to verify this in order to avoid accessing a non-secure website and receiving annoying warnings. Go to the SSLCheck to see which hashing algorithm a certain certificate uses.

All new certificates are issued as SHA-2 as a rule, while existing SHA-1 certificates can be reissued as SHA-2 certificates free of charge.

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