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| bio | website | |
|---|---|---|
| location | Portland, OR | |
| age | ||
| visits | member for | 1 year, 3 months |
| seen | 14 hours ago | |
| stats | profile views | 34 |
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Feb 14 |
awarded | Yearling |
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Jan 14 |
comment |
Why are hash functions one way? If I know the algorithm, why can't I calculate the input from it? @BartvanHeukelom: That's not actually true. Destroying data is irrelevant, the only relevance is the cost of a preimage attack. Using salt does not increase the cost of a preimage attack, it only prevents attackers from running preimage attacks in parallel or ahead of time. Don't misunderstand, salt is essential -- but there is no real benefit for non-injective functions here. |
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Dec 11 |
comment |
Rainbow table concept for Prime numbers The prime counting function is not defined as π(x) = x / ln(x) -- that wouldn't make sense, since π(x) must always be an integer and x / ln(x) is never an integer. Instead, it is approximated by x / ln(x) in a certain mathematical sense. |
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Feb 16 |
comment |
Why are hash functions one way? If I know the algorithm, why can't I calculate the input from it? @drjimbob: Nice! Now here's a link I used: primes.utm.edu/lists/small/small.html |
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Feb 16 |
comment |
Why are hash functions one way? If I know the algorithm, why can't I calculate the input from it? @Mucker: A function f(x) is injective if f(x) = f(y) implies x = y, i.e., no two inputs have the same output. A bijective function is an injective function that is also surjective, i.e., for every possible output there is a corresponding input. When people say "bijective" in this thread they really should be saying "injective". Both concepts are not really relevant to password hash security. Telling you the answer to the reader exercise defeats its purpose, I never wrote down the answer anyway (it does exist, I just don't know what it is). |
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Feb 15 |
awarded | Mortarboard |
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Feb 15 |
awarded | Good Answer |
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Feb 15 |
awarded | Nice Answer |
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Feb 14 |
awarded | Teacher |
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Feb 14 |
answered | Why are hash functions one way? If I know the algorithm, why can't I calculate the input from it? |
