SSL Certificates rely on a "Signing Algorithm" to provide validation of a website’s identity. Currently, SHA-1 is the most popular of these signing algorithms. Evidence shows that the SHA-1 algorithm is is becoming weaker. Due to the ever increasing speed of computers, the ability to produce a forged SHA-1 certificate will soon be a reality. A recent security alert from Arstechica reports that the SHA-1 algorithm underpinning many SSL certificates could become easily compromised by 2018. More here For this reason, the SSL industry is encouraging websites that move to SHA-2 as soon as possible. Using the above checking tool, you can see if your site is in need of an updated certificate.

It’s time to upgrade your current SHA-1 algorithm to SHA-2

SHA-2 is a much stronger algorithm that is not currently known to suffer from the same weaknesses as SHA-1. It is also now widely supported by modern web browsers. Because most of the internet can support SHA-2, Google has decided to start giving a security warning in their Chrome web browser for websites using SHA-1 signed certificates.

SHA Algorithm Warning HTTPS HeadersSHA Algorithm Warning HTTPS Headers

These changes will begin to take effect on September 26th, 2014. Google has decided to encourage an early switch to SHA-2 due to the large body of research on SHA-1’s weaknesses. Here is a more in-depth discussion about SHA-1 deprecation by Google.

How does SHA-2 work?

SHA-2 is a set of cryptography hash functions that work with multiple hash algorithms. It includes multiple variations of cryptographic hash functions such as SHA-224, SHA-256 (the most popular), SHA-384, SHA-512, SHA-512/224, SHA-512/256. The research on this new SHA-2 algorithm by security experts shows that it’s almost impossible to break this structure of multiple hash functions and it should be fully secure for the foreseeable future.

SHA-2 is a mathematical mechanism. It uses a one-way algorithm to produce a string that is unique to every file. This string – called a hash – is a set bit-length (based off the specific SHA function chosen, the most popular of these, SHA-256 is 256 bit. The number following each of the functions denotes its bit-length). So each file that a SHA-2556 hash is taken of will have a unique hash value of equal length. The one-way nature of this function means that if you are given a hash, you cannot use that to recreate or determine what the original file was. When a SSL provider validates you for a certificate, they store the hash value of your specific certificate and it is distributed with your certificate. It is then used to validate the authenticity of your certificate when a client (a user’s browser) connects to your server.

How do I get a SHA-2 certificate?

In order to get a SHA-2 certificate, you have to first pick an SSL provider who is capable of supplying certificates signed by SHA-2. We have researched the market and documented major brands who are signing certificates with SHA-2. These brands are Symantec, GeoTrust, Thawte, RapidSSL and Comodo.

  • Symantec has already migrated their entire product-line of SSL certificates and Code Signing Certificates to SHA-2 algorithm and they had an official blog post announcement.
  • GeoTrust & RapidSSL have recently added support for SHA- 2 in their panels for all of their certificates.
  • Comodo has supported the SHA-2 algorithm for a while and has now made this their default setting for all SSL certificates.
  • Thawte has already had their entire portfolio of SSL certificates to the stronger SHA-2 algorithm and they have already begun issuing SHA-2 based certificate to their customers.

If you already have a current certificate from one of these brands, or another CA who provides SHA-2 certificates, then all you need to do is reissue your current certificate and request it is signed with the SHA-2 algorithm. With the above brands this is done during their enrollment process and it is not required to specify SHA-2 in your CSR.

If your current SSL provider does not offer SHA-2 certificates, or if you do not yet have an SSL certificate, you can purchase a new certificate from a provider who supplies brands with SHA-2 support.

Remember: Always make sure that you have the matching private key for your new/reissued certificate! (If you are told it is necessary to specify SHA-2 in your CSR, you can do so with the below command line if you are using the popular OpenSSL tool:


"openssl req -new -sha256 -key your-private.key -out your-domain.csr" )

If you want to know more about these brands of SSL certificates which include the SHA-2 algorithm please visit the following pages:

"For more information on the SHA-2 Algorithm Migration Click Here"