Blockchain security hash key functions

Security assumptions of hash functions

There are three main security assumptions for hash functions:

1. Preimage resistance: This means that you can't figure out the original input of a hash function just by knowing its output. It's like trying to guess a secret code without any clues. Even if you find a different input that produces the same output, there are countless other possible inputs, so you can't be sure if you found the right one.

2. Collision resistance: This ensures that you can't find two different inputs that produce the same output. If this were possible, someone could create a fake block or transaction that looks legitimate but actually changes the information in the blockchain.

3. Quantum resistance: Just like with public key cryptography, hash functions need to be resistant to attacks from quantum computers. While there is no algorithm that completely breaks hash functions on a quantum computer, there is one that can reduce their security. However, as long as the reduction in security doesn't make the hash function vulnerable, it remains secure.

It's important to note that while most currently used hash functions are considered secure, there have been cases in the past where vulnerabilities were found and the algorithms had to be replaced. But for now, the main concerns are preimage resistance and collision resistance.