well, my understanding of it is simply that by overflowing the numbers you break the reverse relation to the source numbers

you can easily compute them if you know the numbers, but if you don't, and all you have is the outputs, the number of possible guesses required to find the numbers is impossibly large

but yes, i think it's called the "discrete logarithm problem"

i think that is a deceptive name because as far as i can tell, it's the finite field that defines the math, not the integer part, the integer part is sorta encoded in the expression "discrete" meaning - more or less - integer arithmetic

if you did the same calculations but didn't make them overflow at an arbitary field length they would be reversible