Difficult: I do not understand the difference between finding h(m) such that h(m)=y for a given y and finding m' such that h(m)=h(m'). It seems that in both cases, you will first need to decide that h(m)=y, and if you have that what is the point of finding a different m' with h(m')=y? Are we just trying to find a random input that would give an output that we do not know?
Reflective: While I do not see why you would want to find the alternate m', it is a neat idea. The book indicates that hash functions are usually used for electronic signatures. This seems to indicate that for some passwords, I would be able to enter a completely different password and have it work anyway! Does limiting the size of the input (as they do with passwords) help ensure that there is only one solution m such that h(m)=y to avoid duplicate passwords?
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