Integrate gallery 2 with elgg v1.0

I want to integrate gallery 2 with elgg v1.0. The latest elgg platform can Create your own social network, quickly and easily.
www.elgg.org
Whereby user has a two way authentication login and logout from either elgg or gallery 2 platform.
That is users login in elgg it authenticates gallery 2.
I've seen somebody used this on old elgg version,but didn't release the module
Any ideas how to it?