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People who’re dealing with SSL/TLS certificates – especially the first timers – come across a lot of terms that sound more like military code words than product features. And this makes their heads spin like helicopter propellers. If you’re reading this post, then you must’ve experienced a moment like that. One of the terms that fuels (get it? 😉 this confusion is “SHA256 SSL certificate.” In this post, we’ll be talking about what it means and whether you should be using these certificates or not.
Before we get deep into SHA256 and what it is, let us tell you that it’s a hashing algorithm. The term SHA is an acronym for “secure hashing algorithm.” We know that you won’t understand these words, we just want you to remember these words as we’ll be explaining them throughout the article, in the most straightforward possible manner. Ready to learn more? Let’s get started!
form of the original data (text, picture, audio, video, etc.) that looks a lot like a secret code from a James Bond movie.
Here’s the hash of the word “hash:”
Now, from the above piece of data, can you guess what the original data might have been? Well, you can’t, and even super computers can’t. A highly desirable quality of a secure hashing function/algorithm is irreversibility. It means that good hash algorithms work in such a way that they make it impossible to go back to the original data, even with the use of powerful super computers.
Another mandatory characteristic in any hash algorithm is the “avalanche effect.” It means that the slightest of change in the input leads to a drastic change in the output (hash). Let’s see how it happens in the hash of the word “hash.” Let’s just capitalize “h,” and this is what the hash turns into:
Compare the first and second hash. completely different, aren’t they?
Hashing algorithms are used to identify, compare, and run calculations against files, content, and strings of data. They’re highly useful as you don’t have to compare entire data every time.
Don’t worry, we will get to SHA256 Certificate questions in just a bit!
You might know that SSL/TLS certificates work on public key infrastructure (PKI). It means that they’re issued by authorized entities known as “certificate authorities.” A certificate authority is supposed to sign an SSL certificate when it issues it, to make it legitimate. Here, a certificate authority signs the hash of the certificate rather than the entire certificate, as it’s much more convenient. This signature works as a cryptographic proof that a trusted certificate authority issues the certificate, and nobody has tampered with it.
As the certificate has been converted into a hash, the smallest of change in it will cause the entire hash to change. This, in turn, will cause the signature to change. The browser will compare this changed signature to the original signature and will terminate the certificate as invalid.
Thus, hashing algorithms carry the responsibility of legitimizing an SSL certificate. That’s why a robust hashing algorithm is the first thing you need for an SSL certificate.
As you know, SHA256 is the latest hashing algorithm of the SHA (secure hashing algorithm) family. This hashing algorithm was first designed by the National Security Agency (NSA) and published as a federal standard in 1995 by the National Institute for Standards and Technology (NIST). Soon, SHA1 – the first algorithm of the SHA family – became an internet standard, replacing the old algorithms such as MD-5.
Gradually, SHA1 was found to be vulnerable against theoretical attacks, and as a result, NIST started developing its successor, SHA2. In 2002, SHA1 was broken in theory, and therefore, SHA2 became the new internet standard. However, the use of SHA1 wasn’t discontinued until 2015, as it was only broken in theory, not in practice. Today, no major browser supports SHA1.
After SHA1 was deprecated, SHA2 became its successor and became a worldwide internet cryptographic standard. SHA2 is advanced compared to SHA1 as it covers the security holes of the SHA1 algorithm. Both the algorithms are quite different mathematically as well.
However, the major thing that differentiates SHA1 and SHA2 is their bit-length. SHA1 is a 160-bit algorithm. It means that it converts any data into a hash of 160-bit length. SHA2 is quite different in this regard as it offers hash of various lengths, including 224-, 256-, 384-, and 512-bit digests. Algorithms of these lengths are also regarded as SHA224, SHA256, and so on.
So, SHA256 is nothing but the SHA2 algorithm having a 256-bit length. SSL/TLS certificates having the SHA256 algorithm at its heart are regarded as “SHA256 SSL certificates.” SHA256 is the most widely used algorithm as far as SSL/TLS certificates are concerned. That’s why many people use the term “SHA256 SSL certificate.” In reality, it’s an SSL certificate that relies on the SHA256 algorithm.
Yes, absolutely. SHA256 is one of the safest algorithms that you can rely on. How secure is it? Well, it would take incomprehensible time for super computers to crack it. So, until there’s another way of breaking SHA256, you’re in safe hands.
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