21,194 reputation
11432
bio website at.yorku.ca/cgi-bin/bbqa
location Netherlands
age 44
visits member for 3 years, 10 months
seen 5 hours ago

Got a PhD in topology in 98, now a cryptographer.


12h
answered Homeomorphism between plane with different topologies
12h
comment Shamir sharing scheme - Calculating shares
Yes, this seems right to me.
15h
revised Any open set shares boundary with a discrete set
added 343 characters in body
15h
answered Any open set shares boundary with a discrete set
15h
answered Well-ordered set with greatest element is compact
17h
answered proving that a set is closed
18h
answered Calculate how long does it take to complete a task by two workers
19h
comment Problem with understanding proof of Van Kampen's theorem
Write down the part that you don't understand and ask a more concrete question?
1d
revised finding the inverse of a matrx
edited tags
1d
revised finding the inverse of a matrx
typo
1d
revised Limit points Topology
slight expansion
1d
answered finding the inverse of a matrx
1d
answered Limit points Topology
1d
comment Accumulation points and closed sets
This just says that $(x-\epsilon, x+\epsilon)$ is an open set. You can use $\delta = \min(y - (x-\epsilon), (x+\epsilon)-y)$ if you want an explicit $\delta$. The $(x- \epsilon, x+\epsilon)$ is the required open set around $x$ that is contained in $F^c$.
1d
answered Accumulation points and closed sets
1d
comment Derivative of Diffie Hellman
$d$ should be $b$ in the previous comment
1d
comment Derivative of Diffie Hellman
How can he reverse his $b$? (How did Alice do that ?)
1d
comment is the lexicographic order topology on the unit square connected/path connected?
The first refers to the theorem that a linearly ordered space is connected iff it is complete and densely ordered (proofwiki.org/wiki/…). Densely ordered means that between any 2 points always strictly lies a third, which means that there are no points $x < y$ such that $(x,y)$ is empty (and such points are called consecutive; $x,y$ is also called a "jump" then.
1d
comment Derivative of Diffie Hellman
The first one is known as Shamir's three-pass protocol.
1d
answered Derivative of Diffie Hellman