Hash Functions in Cryptography: A Tutorial
Written by  Daisie Team
Published on 8 min read


  1. What are hash functions in cryptography?
  2. Properties of hash functions
  3. How hash functions work in cryptography
  4. Types of hash functions
  5. Applications of hash functions in cryptography
  6. Common hash functions in use today
  7. Hash functions and Blockchain
  8. How to select a hash function

Welcome to this friendly guide on hash functions in cryptography! If you've been wondering about hash functions and their role in cryptography, then you've come to the right place. This guide will serve as your personal tutorial, taking you through the intriguing world of hash functions in cryptography. We'll discover what they are, how they work, delve into different types, and even explore some applications. So, grab a cup of coffee, settle in, and let's get started!

What are hash functions in cryptography?

Imagine you have a long message—perhaps a novel, and you want to create a unique, much shorter representation of it. This is where hash functions come in handy! In the context of cryptography, a hash function is a special type of function used for this kind of job.

A hash function takes an input (or 'message') and returns a fixed-size string of bytes, typically a digital 'digest'. The output—commonly referred to as the hash value or hash code—is unique to each unique input. It's kind of like a digital fingerprint for your data. Hash functions are a crucial part of many cryptographic systems that we use every day— like secure email, digital signatures, and even our favorite cryptocurrencies.

Here's a simple breakdown of what a hash function does:

  1. Takes an input (or 'message').
  2. Processes it using a specific algorithm.
  3. Returns a fixed-size string of bytes.
  4. The output is unique for each unique input.

Now, what makes hash functions in cryptography special? It's their ability to keep our data secure. You see, a good cryptographic hash function has a few properties which make them suitable for security purposes. But we'll get to that in the next section. For now, just remember: hash functions are not some scary technical term. They're simply tools we use to make our digital world a little safer. And with this hash functions in cryptography tutorial, you're taking the first step into understanding that world.

Properties of hash functions

Now that you know what hash functions are, let's talk about what makes them tick. Here are some of the key properties that make hash functions stand out in the world of cryptography:

  1. Determinism: This means that every time you input the same data into your hash function, it will always give you the same hash value. It's like your favorite barista who knows exactly how to make your coffee, every single time.
  2. Preimage Resistance: Fancy term, isn't it? In simple words, it means that if all you have is the hash value, it should be nearly impossible to figure out what the original input was.
  3. Small Changes, Big Impact: Even a tiny alteration in the input—say changing a single letter—should produce a significantly different hash value. It's like baking a cake: change one ingredient, and your chocolate cake might end up tasting like a lemon tart!
  4. Hash Collision Resistance: In an ideal world, no two different inputs should ever give you the same hash value. If they do, it's called a collision. Good hash functions keep these to a minimum.
  5. Speed: Lastly, a good hash function needs to be quick and efficient. In the fast-paced world of digital communication, no one has time to wait for slow hash functions!

By now, you should have a better understanding of what makes hash functions so important in cryptography. They're not just random tools—they're carefully designed to keep our data safe and secure, and in this hash functions in cryptography tutorial, we're just scratching the surface!

How hash functions work in cryptography

After getting to know the properties of hash functions, you may be curious about how these functions actually work in the world of cryptography. Well, let's dive into it.

Imagine you're creating a secret message for your best friend. Here's how a hash function would help you:

  1. You start with your original message. This is what we call the 'input' in hash function lingo.
  2. Next, you feed this input into the hash function. Think of this step like placing your sandwich order at your go-to deli.
  3. The hash function, like a skilled sandwich maker, gets to work. It takes your input and chops and changes it, following its own unique recipe.
  4. What comes out is a scrambled, unrecognisable version of your original message. This is your 'hash value'—the equivalent of your fully assembled sandwich.

Now, here's where the magic happens. No matter how many times you go through this process, as long as your input stays the same, the hash value you get will be identical. But if you change even a single letter in your original message, the hash value will look entirely different. It's like having a custom sandwich for every different order!

So, that's the basics of how hash functions work in cryptography. They take your data, mix it up, and spit out a unique hash value. By doing this, they help to keep our data secure—one hash value at a time. Hope this gives you a better picture in our hash functions in cryptography tutorial.

Types of hash functions

Okay, so we've learned how hash functions work in cryptography. But did you know there are different types of hash functions? Let's get to know them.

  1. MD5: This stands for 'Message Digest algorithm 5'. It's been around since the 90s. Despite its age, it's still used in some places. However, over the years, people have found ways to crack it. Hence, it's not the best choice for new systems.
  2. SHA-1: This one is short for 'Secure Hash Algorithm 1'. It's a bit stronger than MD5. But, like an old car, it's starting to show its age. Researchers have found ways to break it too.
  3. SHA-256: This is the younger sibling of SHA-1. It's part of a family called SHA-2. It's a lot more secure and is currently a popular choice in many systems.
  4. SHA-3: This is the latest member of the Secure Hash Algorithm family. It's not widely used yet, but it's gaining popularity.

These are just a few examples. There are many more hash functions out there. Each has its own strengths and weaknesses, just like superheroes. So, the key is to pick the right one for your needs. And that's what we'll look at in the next part of this hash functions in cryptography tutorial.

Applications of hash functions in cryptography

Now that we've explored the different types of hash functions, let's look at how we can use them in real-world situations. It's like learning how to use a new tool, right? Here are some areas where hash functions play a starring role:

  1. Data Integrity: Imagine you're sending a message to a friend. You want to make sure the message doesn't change while it's on its way. So, you use a hash function to create a hash of your message. Your friend does the same when they receive it. If the hashes match, your friend knows the message is exactly how you sent it.
  2. Password Storage: Websites don't usually store your password. Instead, they store a hash of your password. When you log in, the website creates a hash of the password you enter. If it matches the stored hash, you're in!
  3. File Verification: Have you ever downloaded a file and saw a hash next to it? That's for you to verify the file hasn't been tampered with. If the hash of the downloaded file matches the provided hash, you're good to go.

These are just a few examples of how hash functions can be used in cryptography. They're like the unsung heroes of the internet, quietly making sure everything runs smoothly. We'll dig deeper into more specific applications in the next part of this hash functions in cryptography tutorial.

Common hash functions in use today

Just like we have different tools for different tasks, there are various hash functions available as well. However, some have proven to be more reliable and popular than others. Let's go over a few of the most commonly used hash functions in cryptography today:

  1. MD5: MD5, or Message Digest Algorithm 5, is a widely used hash function. But be careful! While it's popular, it's not the most secure. It's like the old lock on your back door— it does the job, but it's not going to stop a determined burglar.
  2. SHA-1: SHA-1, or Secure Hash Algorithm 1, is a step up from MD5. It's a bit more secure, but it's also not invincible. It's like a standard deadbolt—better, but still not perfect.
  3. SHA-256: As the name suggests, SHA-256 is part of the SHA-2 family. This one is like a high-security lock. It's currently one of the most secure hash functions and is widely used in Bitcoin and other cryptocurrencies.

Remember, choosing a hash function isn't just about picking the most popular one. It's about understanding your needs and selecting the one that best meets them. Think of it as choosing the right tool for the job. And just like that, we've covered another part of our hash functions in cryptography tutorial.

Hash Functions and Blockchain

Now, let's turn our attention to how hash functions play a key role in Blockchain technology. You may think of Blockchain as a public ledger of transactions. But how does it keep all these transactions secure? You guessed it—hash functions!

Let's break it down:

  1. First, every transaction in a block is hashed. The result is a unique hash value—like a special code—for each transaction.
  2. Then, these individual hash values are combined and hashed again to create a single hash value for the entire block. It's like putting all the codes into a safe.
  3. Here's the clever bit: each block also contains the hash of the previous block. This creates a chain of blocks, hence the name, Blockchain. It's like linking all the safes together.

This process makes Blockchain exceptionally secure. Why? Because if you try to change a transaction, the hash of the block changes. And this would break the chain with the next block. So, to successfully tamper with a Blockchain, you would need to alter every single block after the one you changed. That's as hard as trying to lift a whole stack of safes at once!

And there you have it—a simple explanation of how hash functions work in Blockchain. Just another piece of the puzzle in our hash functions in cryptography tutorial.

How to Select a Hash Function

The big question now is: how do you pick the right hash function? It's a bit like choosing the best lock for your door—it needs to be strong and reliable. So, let's explore some key factors you should consider:

  • Security: The most important feature, of course! The hash function should be resistant to attacks and collisions—just like a lock should resist crowbars and lock picks. The harder it is to reverse-engineer the hashed data (we call this 'preimage resistance'), the better the hash function.
  • Speed: While security is paramount, speed is also important. The hash function should operate quickly to avoid any bottleneck in processing—kind of like how a lock should open quickly when you use the right key.
  • Hash length: The length of the hash output is another factor to consider. A longer hash means more possible outputs, making it harder for anyone to find collisions. It's like having a lock with more possible key combinations.

There's no one-size-fits-all answer here. The right hash function depends on the specific requirements of your system. But by considering these factors, you're well on your way to making an informed choice. And that wraps up this part of our hash functions in cryptography tutorial.

So, whether you're selecting a hash function for a secure password storage system, a digital signature scheme, or a new Blockchain project, remember: Security, speed, and hash length are your guiding stars! This knowledge will help you navigate the complex landscape of hash functions in cryptography.

If you found this tutorial on hash functions in cryptography insightful and want to learn more about the subject, check out 'Crypto For Creators, Part 1: The Backbone Of The Digital Economy' workshop by Tom Glendinning. This workshop will provide you with an in-depth understanding of the role of cryptography in the digital economy and help you grasp the importance of hash functions in securing your creative work online.