# What is Hash Function in Cryptocurrency?

The kind of encryption used in blockchain is called a hash function. Hash Function is one-way encryption without a key. What this means is, if, for example, you put the line “What is bitcoin mining?” through movable type’s SHA-256 cryptographic hash algorithm you get the hash value 724b3e1c2da8c82822f137f95f6373369d14c45396c58b754e29ca36c8250db4.

Now the interesting thing about hash functions is that any change in the original input causes a completely different hash value to be made. This randomness ensures that predicting the output is impossible.

So even if the input is “What is bitcoin mining”, the hash value changes to 7337ce9d8bfa81a71aacbe1da7f5b73a39dbcedb033712fb3d0bf5da737d2741. Despite the only change being the lack of a question mark, the hash value changes completely.

**Why are Hash Functions necessary?**

So what’s the point of having a Hash Function in blockchain? Well, it’s simple. One of the main ways blocks in the blockchain are validated is via proof of work. And the work involved is solving a cryptographic puzzle. The cryptographic puzzles have a particular format. The puzzles ask miners to find an input that gives a specific hash value starting with multiple zeros. This means that whatever is put into the Hash Function must return a result that starts with 00000.

There is no way to cheat this as the only way to solve these kinds of problems is by guessing randomly. Thousands of computers in the entire blockchain work tirelessly to find the exact input that will give the desired result. The first person to find the number closest to the exact input earns several Bitcoins.

Once the correct input is found, that particular block is sealed with that number. That number also acts as the proof of work. What the proof of work means is that people have dedicated computational power and energy towards solving that particular problem.

That number is then added to the next block in the blockchain, to prove the legitimacy of that chain. Like that, each successive block is stamped with the sealing number of the preceding block, creating an unbroken chain all the way back to the Genesis block, the first block of bitcoin ever mined.