I want to share WiFi connection via WiFi. Say, I am connecting to hot.A WiFi hotspot with comp.A and I want to share this connection(hot.A) by create WiFi hotspot in the same computer(comp.A) which is connecting to hot.A.

How can I achive this in Ubuntu 12.04 LTS 64-bit?

This can easily done by the app called Connectify in Windows 7.