sure MD5 hashes will protect password from client to Asterisk, but then still need to worry about it from Asterisk to DB (unless I’m not thinking about it correctly- a reasonable possibility).
I’m just doing a paper design from scratch right now before building out the system. All servers will be hardened and protected by ACLs to only enable access to necessary ports. In theory the network between Asterisk servers and mySQL DBs will be “trusted” so don’t need transport integrity + privacy, but I want an added layer of security to protect billing integrity of users/customers against internal threats (i.e. reduce the ease of employees or admins sniffing user passwords and masquerading- they still can do it if they have access to right systems, but it will be harder to do so without being tracked, unlike an anonymous ethereal trace).
Other scenario this flexibility would enable is Asterisk server traversing non-trusted networks to reach mySQL DBs. An overall simpler approach may be to use IPSEC VPNs to traverse non-trusted networks and keep the application stuff simpler and more scalable (i.e no crypto), but then need another scalable IPSEC box and resiliency and yada yada.