1. In the following network diagram, nodes A, B, C, and D have data to send to each other. B A D Z a) How many keys are required such that the four nodes can communicate with each other in a bidirectional secure way using a symmetric encryption algorithm? b) How many keys are required if the symmetric algorithm is replaced with a public key cryptography system such that the four nodes can communicate securely? c) How many keys are required for secure communication among 100 users if: i. Symmetric key cryptography algorithm is used? ii. Asymmetric key cryptography algorithm is used?