Eh? I think we're working off different definitions of darkNXT!
- NXT that is in an account that nobody knows the passphrase of == darkNXT
- NXT that is in an account that hasn't yet got a public key in the block chain (i.e. no transfers out, no aliases, no forging) != darkNXT
That 250million figure is including the latter, right? No way to distinguish between the two from a technical point of view.
I think you are confusing things, there are 2 different possibilities:
NXT sitting in an account that does not have a public key in the blockchain.
NXT sitting in an account that has a public key in the blockchain, but where the passphrase/privatekey is lost.
The former is "hiberNXT" and most will probably be recovered some day (2^64)
The latter one is truly "dead" and will prob never ever never be recovered (2^256)
Also, the former can be broken into 2 categories:
An account where a person does know a passphrase to unlock it (one of 2^256 private keys, but still crackable by 2^64 since there is no public key published). This was done by a person wishing to stash their NXT somewhere; I would consider this to be dumb; the account should publish its public key so as to not be crackable by 2^64 and to obtain 2^256 security. The person knowing that passphrase can still unlock the account and send the NXT.
An account where a person does NOT know a passphrase to unlock it. In this case nothing cand be done until the account is cracked in a few years.