CHAP over Frame Relay

Consider two routers connected back-to-back like this

Router1 ---- [Frame Relay Cloud] ---- Router2

Here is the relevant config for the routers

Router1

interface Serial2/0
ip address 150.150.12.1 255.255.255.0
encapsulation frame-relay
no keepalive
no fair-queue
frame-relay interface-dlci 102

Router2

interface Serial2/0
ip address 150.150.12.2 255.255.255.0
encapsulation frame-relay
no keepalive
no fair-queue
frame-relay interface-dlci 201

The two routers can successfully ping over the frame relay interfaces.

Now, we wish to run CHAP between the two routers over the frame relay link for security reasons. How will the config need to be modified to make that happen? Assume that the usernames to be used for CHAP are the router hostnames itself and the password for both routers is "cisco".