Yea, u have to clear security n go up one level to the departure gates.
55 mins is do-able.
Just hope that there is no long line at security n your incoming flight isnt delayedtoo long.
Sometimes, the security line can get really long.
That is the one thing i dislike about icn.

It can also be a really long walk from plane to security transit.

I have seen the airlines hold up departures for connecting pax.
Once i got through security with 20 mins to spare, ran to the gate n found out it was delayed for connecting pax.