Can I use NXT private key to hold N2?
No, don't do this with any Nxt clone. It is unsafe unless the Clone has changed the transaction format. But even then I wouldn't do it.
A 'Clone Attack' is thought to be possible by Come-from-Beyond and a couple of Nxter's are working on proving it.
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Clone Attack Clone Attack is a scheme for stealing NXTs through the use of a Nxt Clone and
can only be successful if you use the same passphrase on Nxt and on a Nxt Clone that uses the same transaction format. Very Important: Do not use your Nxt Account passphrase for anything but your Nxt account. The Clone Attack is a very simple attack so could become common if people are reluctant to generate new Strong Passphrases and reuse their Nxt Passphrase in any Clone. It is described below using a fictitious clone named NEX:
1. You use the same account passphrase in NEX as you have in Nxt.
2. The attacker sends you an amount, say 10000NEX, perhaps at the launch of the Clone, as a giveaway or as part of day to day transactions.
3. Later, the attacker offers to buy 5000NEX from you for 0.01 BTC (this will always be a generous offer for the Clone).
4. The Attacker sends you the Bitcoins in advance and you send him 5000NEX.
5. The attacker then broadcasts the NEX transaction you sent them onto Nxt network, .
Result: 5000NXT is removed from your Nxt account and you only received a small percentage of its value. Again, very important: Do not use your Nxt Account passphrase for anything but your Nxt Account. Anyone can broadcast transactions from a Clone into Nxt and vice versa, if the clone doesn't change the transaction format used in Nxt. So anyone who uses the same Account Passphrase in both can lose NXTs.
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Source: The
Nxt Glossary http://wiki.nxtcrypto.org/wiki/Glossary
