How to properly implement the Diffie-Hellman algorithm?

Question

Cryptography

Hello, I want to do something like an anonymous group chat. DH was chosen as a protocol for obtaining a shared key, there are a couple of questions about its implementation:
1. What are the requirements for a generator[g] and a prime number[p]? I heard something about “special” numbers from RFC, which supposedly can be sewn into the client and not worry about how reasonable their use is?
2. How should the exchange of public keys go for the number of users > 3?

Answer 1

1. It is possible to sew up constants from RFC in the client and not to be soared. Their knowledge threatens nothing.
Counter question - how do you intend to secure the exchange of open components?
2. The best way, IMHO - each with each.