How many keys are required, if you are to ensure a secret communication for every possible pair of communicating parties

7140 pairs of key

Explanation:

In calculating the number of pairs of keys required, the formula to be used is

n * (n−1) / 2

So for example, if we're to consider 120 users. This means our n is 120, and thus applying it in the formula would yield the calculation

120 * (120-1) / 2 =

120 * 119 / 2 =

14280 / 2 =

7140 key pairs.

Therefore, we boldly state that be number of pairs of key required is 7140

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