Today we’re going to talk about something that might seem like common knowledge, but is actually quite fascinating: the hidden property of hash functions. You know how hash functions are supposed to be one-way encryption?

First things first, what makes hash functions so special in the world of cryptography. They take an input (let’s call it “the message”) and output a fixed-length string (called the hash value or digest). This is great for security purposes because if someone intercepts your message, they can’t reverse engineer the original text from just the hash value that would be like trying to find a needle in a haystack.

But here’s where things get interesting: did you know that hash functions are actually collision-resistant? That means it’s almost impossible for two different input messages to have the same output hash value. This might not seem like a big deal, but think about what this really means if someone tries to tamper with your message and change it slightly (let’s say from “hello” to “hell”), they won’t be able to create a new hash value that matches the original one.

So how does this work? Well, let’s take an example. Let’s say you have two messages: “hello world” and “world”. If we run these through a hash function (let’s use SHA-256 for simplicity), we get the following output hash values:

– “hello world”: 9f86d081884c7d659a2feaa0c55ad015a3bf4f1b2b0b822e45d6ba57898dc2a3
– “world”: e10adc394edaeae0571e0e2d69ea7efi60be4355abebbc85cd69b2455aa76bf

As you can see, these hash values are completely different. Even if we change just one letter in the message (let’s say from “world” to “worl”), the output hash value will be entirely new:

– “worl”: 392febdceb5bd479ea76a0ab010e56bf85845d85a410aff2fb98da62ad7ca6a4

So, what’s the big deal? Well, let’s say you have a message that needs to be signed digitally. You can use your private key (which is like a secret code) to create a hash value of the message, and then sign it with your public key (which is like a signature). When someone receives this message, they can verify the digital signature using your public key but if anyone tries to tamper with the message or change even one letter, the output hash value will be completely different. This means that the digital signature won’t match up anymore and the receiver will know that something is fishy!