Do you know what KSSN & KARCN stand for?
If you know at least;
a, What they stand for
b, Actually have one of the two
Then you can register on Korea here;https://signup.ndoors.com/Join/Ndoors?site=ATLANTICA
Basically the three options represent:-
Sign up (18+) > Sign up (Under 18) > Foreign Sign-Up
For the first two you'll need either a KSSN or I-Pin
For the third you'll need a KARCN or I-Pin (Note if your I-Pin is an alien version you'll need to use this option regardless)
Beyond that it's pretty straight forward.
이름 = Name
주민등록번호 = Social Security Number
외국인등록번호 = Alien Registration Number
KSSN = Korean Social Security Number
KARCN = Korean Alien Registration Card Number (You'd need the Alien Registration Number off it)
For the most part you'll only ever have a KARCN while staying in Korea for 90+ days, after which you'll have to return the card when you leave the country (It'll just be voided anyway, so the number won't be usable afterwards) or acquire citizenship, which you'll get a KSSN anyhow.
You could also just borrow a friend's number(s), but most Korean's won't give out that information willingly because that number is practically the same as their life and can be used to identify them easily; so to give out that number basically leaves them open to identify theft. A few of our players who play Korea basically have had friends create the accounts or just use their account; so they don't actually know the person's security number.