You understood my question better than I did. Thank you.
Is the following paragraph correct?:
If I had unlimited computing power, I could search for all the inputs that return 37ecb0a3164e6422bedc0f8db82e45ec from the MD5 function. Then I could search those inputs and see which ones are meaningful sentences in English, and then make an educated guess at what the message is. But in reality, it would take too much computing power to find even a single string that returns 37ecb0a3164e6422bedc0f8db82e45ec.
It's not quite correct, but you've broadly got the thrust of it.
When two different inputs produce the same output from a hashing function, this is called a hash collision. Finding collisions in the SHA256 hashing function is part of how bitcoin mining works. It is very computationally expensive (which is kind of the point, re: bitcoin mining), but it's certainly tractable to find some input that generates the same output as another one.
If you were to try and search the space of all possible inputs for MD5, you'd quickly(ish) find an input that collided wit...
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