  Suppose there is a group of N people some of whom possess a specific
property. For example, their wealth is above or below a threshold, they voted
for a particular candidate, they have a certain disease, etc. The group wants
to find out how many of its members posses the property -- without revealing
the identities. Unless of course it turns out that all members do or do not
have the attribute of interest. However, in all other cases the counting
algorithm should guarantee that nobody can find out if a particular individual
possesses the property unless all the other N-1 members of the group collude.
  The present article describes a method to solve the confidential counting
problem with only 3*N-2 pairwise communications, or 2*N broadcasts (the last
N-1 pairwise communications are merely to announce the result). The counting
algorithm does not require any trusted third parties. All communications
between parties involved can be conducted in public without compromising the
security of counting.
