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Sep
24
awarded  Autobiographer
Mar
7
comment Computational feasible to reverse MD5SUM?
Interesting, even though I'm less about MD5 now and actually looking for easy collisions. Incidentally, I can't control the file contents per se but I can decide where to begin and stop reading from the input stream, to process as segments. So something using a Rolling hash might apply.
Mar
7
awarded  Supporter
Mar
7
comment Computational feasible to reverse MD5SUM?
@poncho You are perhaps alluding to the Pigeonhole principle. I am just experimenting/designing an algorithm that tries to make that irrelevant by compensating in other ways.
Mar
7
comment Computational feasible to reverse MD5SUM?
Stemming from the Chinese engineer's algorithm linked above, it wasn't hard to soon find programs like md5clone.exe and evilize for Unix. The difference seems to be that they can control both images, whereas I can't control the first image; taken purely as data input. Anyway, I am actually less interested in MD5 itself, than in another way of hashing uncontrolled data that's more easily clone-able. You pointed out CRC, good--somehow thinking of that I confused it with MD5 earlier (huge diff I know)
Mar
6
awarded  Scholar
Mar
6
comment Computational feasible to reverse MD5SUM?
Excellent and informative reply.
Mar
6
accepted Computational feasible to reverse MD5SUM?
Mar
6
comment Computational feasible to reverse MD5SUM?
You're both right, apparently what I was asking for was a hash preimage. My question was really just a stepping stone to another exploration, which is: what other well-known hashing functions do make it easy to find preimages, yet such that I only need store that hash + some kind of seed much shorter than either m or m', to allow me to regenerate that image or preimage again?
Mar
6
comment Computational feasible to reverse MD5SUM?
of interest: mscs.dal.ca/~selinger/md5collision
Mar
6
revised Seeking special-use fingerprinting/hashing algorithm
linked to related puzzle
Mar
6
asked Computational feasible to reverse MD5SUM?
Mar
6
comment Seeking special-use fingerprinting/hashing algorithm
I guess SciComp was too small so they moved it here. Encryption is not my goal but it could get used that way. This is just experimental, one component for theory testing. I wanted to find out about already known hashing recipes, that are practically two-way to somewhat interchangeably swap data blocks with others; which to implement seems to need the properties above.
Mar
6
revised Seeking special-use fingerprinting/hashing algorithm
grammar
Mar
6
awarded  Editor
Mar
6
revised Seeking special-use fingerprinting/hashing algorithm
tighten properties
Mar
6
awarded  Student
Mar
6
asked Seeking special-use fingerprinting/hashing algorithm