In order to ensure secure communications between everyone in a population of n people a total of n -LRB- n & minus ; NUMBER@1 -RRB- / NUMBER@2 keys are needed , which is the total number of possible communication channels .

In order to ensure secure communications between everyone in a group of n people a total of n -LRB- n & minus ; NUMBER@1 -RRB- / NUMBER@2 keys are needed , which is the total number of possible communication channels .
