i get that SHA256 isn’t considered “encryption”, it’s something to do with hashing. so, if i encrypt “hello” into a random string of characters, why is it said to be impossible to decrypt it back to “hello”? if you had a maths equation like P = (k * 10 / G) / (4x * 5gl), it’s possible to work backwards to find the value of k or g eventually. why not with SHA256? is it something to do with random numbers?
In: Mathematics
There are two ways to design secure hash functions.
One of them is to pick a mathematical problem that is difficult, like factoring two integers. Then you design an operation where reversing the hash function is equivalent to reversing the mathematical operation.
This is almost never done, because the hash functions are incredibly slow.
Instead, what we have done is identify a bunch of properties of hash functions we think they should have. These have been based on a hundred years of attack on various forms of cryptography – we know that certain properties are resistant to entire swathes of attacks. We then design hash functions that have these properties.
This is how the whole SHA family was designed.
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