thx, ricot,
ok, understood. usefull for users typing in account numbers but this doesn't answer my question.
this doesn't help to prevent sending funds to hiberNXT, or does it and if, could you please explain how?
as said, i am currently on this, therefore i would like to understand the whole procedure.
from what i see the main problem is to copy or even type a number to send funds to
which is not the intended number and therefore the funds are lost in hiberNXT.
is this what we are talking about?
Well, the chance that, by randomly typing that new kind of identifier, you get to a valid account is 1 in 2 million. So money sent to the wrong address because a cat walked over my keyboard should be dealt with.

The only other option to send it to an unknown account is if someone logs into an account, gets the identifier from there and then looses his password. (Or he mistyped his password on the first try). This you can only avoid by making sure that the password is correct. That's a pure UI thing in the client and shouldn't influence account numbers.
So if someone logs into an account, and gives you the new identifier, it's very very hard for you to send it to another account.
