how to write pam modules for keyboard interactive method

[Kapileswar Rao .B]

Hi,

   I want to write pam module for challenge response based authentication 
with keyboard interactive authentication method on both sshd (server) and 
ssh (client) side. How should I write the pam modules. What is the general 
protocol between pam functions and the calling functions. What information
does the sshd gives to the pam module how can the pam module send the 
information back to sshd.

Are there any already implemented pam modules which work with keyboard 
interactive authentication method. If so plzz give me pointers where can I 
get them. 

Anticipating quick replies

thanks!
kapil