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comment RSA with modulus n=p²q
if j and k have a common factor i, then n has an integer ith root. This will be easier to factor to recover p and q.
Jun
26
comment Do sites store login password with hash? If so, can people can use hash collision to log in?
It can happen but don't underestimate the effort of step 3. Also it's better than the alternatives. Storing plaintext means that B is done at step 2. Storing encrypted passwords means B just needs the key, which is stored in process memory.
Jun
9
comment How can one detect if a hash function doesn't have a full image?
The only information you get is based on collisions, so it takes ~2^n/2 calls before you get any information. For n large enough, that means you can't tell. Otherwise, it's an exercise in estimating size based on collision rate and figuring out when you have achieved statistical significance.
Jun
4
comment Padding to increase entropy and size of (otherwise) small JSON objects
Or use a fixed-width number format like 0x00000007 and 0x0000007B
Mar
28
comment Generating shared secret random permutation
Are you familiar with Mental Poker? en.wikipedia.org/wiki/Mental_poker
Feb
18
revised Block Cipher vs Stream Cipher in Web Application
expand answer
Feb
18
answered Block Cipher vs Stream Cipher in Web Application
Jan
24
comment Symmetric encryption is no longer necessary?
Where is this quote taken from?
Aug
29
awarded  Supporter
Nov
11
awarded  Editor
Nov
11
revised Can there be two hash functions without common collisions?
add concession
Nov
8
comment Can there be two hash functions without common collisions?
Stephen, that actually depends. If the pigeon hole argument applies, then of course any hash has a collision. If we can restrict the input space to be not bigger than the output space then this is not true: consider the function F(x) = 0 which makes G(x) = x.
Nov
8
awarded  Teacher
Nov
2
answered Can there be two hash functions without common collisions?