1,271 reputation
135
bio website
location Portland, OR
age
visits member for 2 years, 8 months
seen Oct 19 at 6:52


Sep
24
awarded  Autobiographer
Sep
16
comment JSON Web Tokens (JWT) as user identification and authentication tokens
GCM is an authenticated encryption mode, so it does provide authentication.
Feb
14
awarded  Yearling
Dec
26
awarded  Cleanup
Dec
26
comment Why are hash functions one way? If I know the algorithm, why can't I calculate the input from it?
@juanpastas: Your edit is incorrect. If you use the product xy as your password, then the scheme does not work. The password is both numbers, and the product is stored in the password database.
Dec
26
revised Why are hash functions one way? If I know the algorithm, why can't I calculate the input from it?
rolled back to a previous revision
Oct
28
awarded  Great Answer
Feb
14
awarded  Yearling
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.
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.
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
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).
Feb
15
awarded  Mortarboard
Feb
15
awarded  Good Answer
Feb
15
awarded  Nice Answer
Feb
14
awarded  Teacher
Feb
14
answered Why are hash functions one way? If I know the algorithm, why can't I calculate the input from it?