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RolyPoly
Symmetric-key encryption scheme In my notes, it says there are three problems associated with symmetric-key encryption schemes. One of them is complex key management. It states that for n users, we have nC2 keys. Why is it nC2?
If you want to use symmetric keys, every combination of two users should have an unique key. nC2 is the number of possible combinations of two users. If you have a list of n users you need to find sequences which select precisely two elements. It's combination since (User1, User2) is the same as (User2, User1) (both users will get the same key).