What is Digital Signature Algorithm - Definition | Types | Examples

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The COVID-19 pandemic changed the working process, making many people work from home. You've probably signed important papers online because we couldn't meet face-to-face. A global standard known as the Digital Signature Algorithm has been established to ensure these digital signatures are genuine and trustworthy. In addition, it helps keep important info safe when we can't be in the same place. Before proceeding further, we will learn about digital signatures in brief.

What is a Digital Signature?

Digital signatures are a virtual lock and key for significant files. They help make sure documents are simple and unchanged when sent between people. In short, it's like having a secret code. A unique code is used to lock a message or the public key. Only the correct key, or the private key, is used to unlock the message. However, for digital signatures, the process is reversed. The private key is used to lock the signature rather than the message. The signature can be unlocked by anyone who possesses the matching public key. As a result, it helps us to ensure that the proper key was used and that the signature is authentic.

What is a Digital Signature Algorithm (DSA)?

The Digital Signatures Algorithm is a code approved by the government to sign digital things. They established it in 1991 and said everyone should use it in 1994.

This code helps in three ways:
 

1. Checking who sent the message: You can be sure who sent it with the help of the suitable key combo.
2. Ensure the message isn't changed: You can’t tamper with the note unless you have the appropriate key; it will not even unlock.
3. Stopping someone from saying they didn't send the message: If the signature is correct, the sender can't deny sending it.

What is the List of Digital Signature Algorithms?

Now, we will show you the list of DSA algorithms.

1. Signature verification
2. Elliptic Curve Digital Signature Algorithm
3. Key
4. ElGamal encryption system
5. Ggh signature scheme
6. Message digest 
7. DSA
8. Group signature
9. RSA
10. Signature algorithms

Here, we have described the digital signature algorithm list. Now, we will elaborate on the steps involved in the algorithm for digital signatures.

Steps Required in DSA Algorithms
 

1. Creating Keys

• Choosing Parameters: First, pick a secret code length (H) and decide how long it should be. Then, choose another length (L), a multiple of 64, between 512 and 1024. The values should follow some rules.

• Getting Prime Numbers: Choose two unique numbers (p and q) based on the lengths chosen earlier. There are some rules to follow here, too.

• Algorithm Parameters: p, q, and another number (g) shared among users.

• User Keys: For each person, choose a secret number (x) and use it to create a public number (y).

2. Making Signatures

• Hashing: Change the original message into a secret code using a specific function (H#).

• Generating Signature: Using some math and randomness to create two numbers (s and r). Package these with the original message.

3. Sharing Keys

• Keeping Secrets: The person signing keeps their secret number (x) a secret. They share the public number (y) openly.

• Signing: When signing a message, choose another secret number (k), do some math, and create two new numbers (r and s). There are rules to follow here, too.
   

4. Checking Signatures

• More Hashing: Change the original message again using the secret code.

• Verification: Do some more math with the received signature and original message. Additionally, check if it matches the numbers sent with the message.

Understanding how the DSA Algorithm works is the best opportunity for all. However, it's also important to know why it's good compared to other ways, like the RSA algorithm.

Algorithms’ Correctness

In short, the DSA Algorithm is a special math formula. To check if it's working correctly, we use some equations. One of them looks like this:

s = (k^(-1) * (H(m) + x * r) ) mod(q)

And another one:

k = H(m) * s^(-1) + x * r * s^(-1)

These equations help us make sure everything is correct. We also use some letters like 'w' to make it easier. After doing the math, we get a final result that proves the algorithm is correct. In other words, it's like checking if one side of an equation equals the other hand, and if they match, we know it's working.

How DSA Works?

DSA involves two keys,i.e., a private key (like your secret code) and a public key.

• If you're the one who sends the message, you use your private key to create a remarkable signature for it. 
• You send your message with the unique signature you created.
• Now, when your friend receives the message, they use your public key (the decoder you gave them earlier) to check the particular stamp. 
• Even though your friend doesn't know your secret code (private key), the algorithms help them verify if the stamp is genuine. If it is, they comprehend the message is untouched and came from you.

So, DSA acts like a magical guardian for our digital messages. However, it ensures they stay safe and sound during the algorithm from sender to receiver. Alright, we’ve learned about the workings of it. Now, we will learn some advantages and disadvantages of it.

Learners Also Read:- Data Structures and Algorithms in Python - Comprehensive Guide

Pros of Algorithm For Digital Signature
 

• The Digital Signature Algorithm is the most secure and stable method to check for genuine signatures compared to other methods.
• Making secret keys with DSA is like lightning! It happens way faster than when using the RSA method.
• DSA requires less space compared to other signature verification methods.
• When the National Institute of Standards and Technology shared DSA with the world, they made sure nobody had to pay to use it.

Further, we will elaborate on some downsides of DSA algorithms.

Cons of Digital Signature Algorithm
 

• DSA has a limit on the length of its secret keys, which makes it unsuitable for some tasks.
• To use DSA, you need to follow strict rules regarding the length of your secret keys.
• Additionally, DSA does not work well with certificates, which makes it less convenient for specific jobs.
• When DSA applies its signature to something, it becomes permanent and cannot be altered or undone. 
• Although DSA is a newer method compared to older, more established methods, some people might not trust it as much because it has not been around for as long.
• Finally, when DSA signs something, the resulting signature can be larger than signatures made with other methods. As a result, it could slow down the process of storing or sending things around.

Now, we will learn an example of it. 

Digital Signature Algorithm Example

Alice has a message (let's call it M) that she wants to send to Bob. But she doesn't just send the message as it is. She wants to make sure Bob knows it's really from her. Here's how she does it:
 

• First, Alice creates the message (M) she wants to send to Bob.
• Alice gets creative and makes up a random number (let's call it k). She then does some math with this number and comes up with a new number.
• Now, there's some more math happening. Alice uses this new number along with a few other things, like a secret code (her private key) and a specific function (a bit like a secret handshake) to create another number. This number is part of what makes her message unique.
• The unique numbers Alice got from all this math form her digital signature (let's call it S). It's like a seal she puts on her message to prove it's really from her.
• Now, the message (M) and the special seal (S) are sent off to Bob. It's like sending a letter with a unique stamp to show it's legit.
• So, in the end, Bob gets the message and can check the seal to be sure it's genuinely from Alice. It's like a high-tech way of saying, "Hey, Bob, this is me talking.

Concluding

In today's digital world, how much we can rely on our messages and online deals depends on how substantial and reliable our digital signature systems are. Once we understand how they work and where they are used, we can move around the internet feeling safe. Moreover, we know our information is safe and online talks are private. As technology gets better, digital signature algorithms will be even more important to keep our online world safe and sound.

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