What is the hashing algorithm called used in Bitcoin?
SHA-256
Why is this hashing algorithm really hard (almost impossible) to brute-force?
My understanding of it is linked to the number of different hashing values that the hash function can produce. During this couple of lectures, I in the beginning had a hard time seeing why you just couldn’t reverse engineer the hash value to the input if you will know for example the SHA 256 algorithm. With a search on google I found easy explanation of it, for example introducing some concepts around “clock arithmetic” and simpler ones like if you pick two random numbers between 1 and 9999 that you add together which results in your hash value. The last one will even be hard to reverse engineer to the input if you for example add the numbers 2+300=302, it will be hard for anyone to reverse engineer on the first try that the hash “302” will be your input 300 and 2, it can be a lot of other numbers as well.
My understanding why Bitcoins hashing algorithm “SHA-256” is almost impossible in the present moment is for the fact that it is consider to be impossible today to reverse engineer and the 256 bits hash output value is consisting of a HUGE number of different values so a brute-force in todays day and age is consider infeasible and practically impossible.