###
L. Csirmaz:

##
Secret sharing on the infinite ladder

The notion of *perfect secret sharing scheme* has been extended to
encompass infinite access structures, in particular infinite graphs, in
[2]. The participants are the vertices of the
graph *G*$ and
the edges are the minimal qualified subsets. The *information ratio*
of *G* is the largest lower bound on the amount of information by secret
bits
some vertex must receive in each scheme realizing this access structure.
We show that this value is 7/4 for the infinite ladder,
solving an open problem from [2]. We give bounds for other
infinite graphs as well.