Deterministic
No matter how many times you input the same data, you will always get the same result. If you got different results each time, it would be impossible to keep track of the input.
Quick Computation
SHA 256 is capable of returning the hash of input quickly, meaning it is an efficient process.
Pre Image Resistance
This refers to how difficult it is to determine the original input based on the hash output. Because SHA 256 produces a 256-bit hash, it would take so long to break Pre Image Resistance by brute force, that it doesn’t really matter (although it is not impossible).
Small Changes in the Input Changes the Hash
Using SHA 256, even something as small as changing an upper case letter to lower case letter will drastically change the hash output.
Collision Resistant
A collision is when two different inputs end up with the same hash output. While this is not impossible, it is highly unlikely with SHA 256. Because there are 2^256 different hash output possibilities, each individual input, generally speaking, will have its unique hash output.
Puzzle Friendly
Definition: For every output “Y”, if k is chosen from a distribution with high min-entropy it is infeasible to find an input x such that H(k|x) = Y.
Specifically in bitcoin mining, k is a random value generated from a wide distribution, which is concatenated to x, the hash of the original input. The new string is then hashed to produce Y, the outcome, which is compared to the difficulty level. This process is repeated over and over until the requirements are met and the new block is added to the chain.
All of these six properties combined make SHA 256 exceedingly difficult, if not impossible to brute force.
What is the hashing algorithm called used in Bitcoin?
-> SHA 256
Why is this hashing algorithm really hard (almost impossible) to brute-force?
-> SHA 256 hash has 2^256 different possibilities. 2^256 is a 78 digit number. This is a huge number of possible combinations. The best comparison that I personally so far heard regarding this, to gain an better understanding how great this number is, was when a teacher claimed that “the possible combinations is almost as big as all atoms in our so far known universe”. A mind blowing thought that give a very good explaination for Ivans question!
1. What is the hashing algorithm called used in Bitcoin? Sha 256 is the hashing algorithm used in Bitcoin.
2. Why is this hashing algorithm really hard (almost impossible) to brute-force?
Blockchain is immutability because any changes in the blockchain are noticed and nullified by each preceding block. This immutability makes it very hard to use the brute-force method.
1. What is the hashing algorithm called used in Bitcoin? Sha 256 is the hashing algorithm used in Bitcoin.
2. Why is this hashing algorithm really hard (almost impossible) to brute-force?
Blockchain is immutability because any changes in the blockchain are noticed and nullified by each preceding block. This immutability makes it very hard to use the brute-force method.
1.) (Secure Hashing Algorithm) SHA-256
2.) Due to the large amount of information in the SHA-256 hash rate it would be nearly impossible to brute-force to find the correct hash input/output and wouldn’t be worth it to even try.
Answer the questions below
1.What is the hashing algorithm called used in Bitcoin?
SHA-256 (Secure Hash Algorithm)
2.Why is this hashing algorithm really hard (almost impossible) to brute-force?
while it is possible to break pre-image resistance via the brute force method, it takes so long that it doesn’t matter.
EX: abc
acb
bac
bca
cab
cba and that’s it right? a few seconds tops no biggie!
ok now try that with one of these…
2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824
(knock yourself out)…hash it out?
secure hashing algorithm
What is the hashing algorithm called used in Bitcoin?
SHA-256
Why is this hashing algorithm really hard (almost impossible) to brute-force?
Because solution string is randomly produced taking k|x phrase to confirm Y hash. Solving a puzzle with different aleatory values such as Nounce + previous Hash and difficulty
Great answer @bazooquanox 
I missed the first time, didn’t notice you answered your question one post up, guess I was a bit careless
SHA 256
SHA-256 generates 256 bit hash. which means to brute-force this hash, someone has to select an input randomly out of 2^256 possibilities. In average case scenario someone will find the answer after 2^128 attempts which is too long and hence almost impossible.
SHA-256
It takes a lot amount of time to brake pre-image resistance.
I was having a really difficulty time to answer the second question, your answer helped me understand the article a lot. thanks
The algorithm used by bitcoin is called Secure Hashing Algorithm 256 aka SHA-256.
There are too many inputs to try, that it is simply not worth the time you would have to spend to brute force.