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Without wasting any much time, let us get started with the next important concept in cryptography that



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is Hachim.



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You must have heard about this dumb harshing, which is very common if you want to check something.



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So whenever you're going to download a software, you might see a line over there saying that, please



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check the hash here.



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So what exactly is harshing?



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Harshing is transforming the normal text, the normal message, our data into a Jibberish one.



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So it sounds funny, right?



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Why we should transfer transform something which is understandable into something which is not completely



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understandable, but it's it's abrupt text.



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So why we should do that?



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Well, hashing is a mathematical function which converts a numerical input value into another compressed



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numerical value of the same length.



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For example, if you enter my name is X, Y, Z, the output will be some gibberish data.



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And but if you enter, my name is ABC again, the output will be different.



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So no two hash values can be seen.



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So then when we pass the input to the hash function, the output is known as the message digest.



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Basically it digests the input and then gives us the output of the origin message, which is known as



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a message digest.



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So MI five, that is message digest, fifth version or secure hash algorithm.



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SHC one is two and three are three different hashing algorithms which are used now.



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Hashing algorithm is again our M.D., which is res integrated message digest function basically.



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So let us consider we have a document here and you want to transfer that document to Alice over the



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Internet, but it has some confidential data.



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OK, it has some confidential data and you don't want to transfer the original document as it is.



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So what you do is you give the original document into hash algorithm and together you get a hash document.



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So this is the working of a hash function.



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So when it comes to hashing, what you have to remember is these are the most common hashing algorithms.



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And all of this as this as a tool is widely used because it has more rounds, it has more keys to it,



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which prevents the data integrity.



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So when you when do you have to use a hash?



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OK, let's consider you are downloading a new program from Microsoft.



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And Microsoft has said that the hash value is A, B, C, D and E, so if you download the software,



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make sure that you hash this software and check if the values are seen.



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So if both the hash values are the same, then you have downloaded the original software.



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Let me tell you one thing that even a single character in the file changes, the entire hash value is



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going to change.



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This point is very important.



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So in order to maintain the integrity of data, you check the hash value.



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Another scenario can be, let's say Alice has said hello to Bob.



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Hello, I am Alice and I want to meet you at three p.m. and Bob receives a message.



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It's Hashd.



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And if you change the message to Hello, I am Alice, I want to meet you at three thirty.



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The hash value of both the messages will be different.



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So in that way, hashing is used in digital signature Ghadames.



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You must have heard of the word digital signatures.



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So in the next lecture we will have one fun activity that will be calculating different hashes and will



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see how changing one character can change the entire hash value.



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All right, stay tuned.



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Keep moving forward.