Hi /g/ can you solve this puzzle
A group of 421 people plans to use symmetric encryption for secure communication.
How many keys are needed to let everybody communicate with each other?
>>53932117
n(n-1)/2
1
How about you solve it yourself asshole!
422
About fitty
>>53932117
0
People don't need secure communication in order to be able to communicate.
>>53932117
420+49+418+...+3+2+1
>>53935130
so this, senpai?