Restoring private key from old bitcoin wallet I have old bitcoin wallet with some (not very huge) amount (last transaction was on 2014). It was created in Multibit (Classic, I guess, then I had old computer with old OS). Now I have new device, system and wallet, and want to restore old [wallet] to send bitcoin to the new one. I know, I need a private key, so I imported old wallet (it's watch-only wallet right now) in Bitcoin Core with rescan and next try to do like this guy -&gt; https://www.youtube.com/watch?v=8Ev33XGCH8M, however, after putting &quot;dumpprivkey&quot;-command in console, it says &quot;the private key for this address is not known&quot;.
That's what I don't understand (interesting, though), b'cause I remember I've backuped it and hold those files for all those years on my USB stick, but now they're completely unusefull. :(
How can I resolve this problem? Anyone knows?
If you &quot;imported&quot; something from your old Multibit Wallet and ended up with a &quot;watch-only wallet&quot; it means that what you &quot;imported&quot; was a Bitcoin-address and not a private-key. You must find and import the private-key, not the Bitcoin-address if you want your new wallet to be able spend the money.
If your old Multibit Classic software is still working, you should be able to use it to create a transaction that sends money to a receive-address you create in a new wallet (using some different wallet-software such as Bitcoin-core).
I think a lesson for the rest of us is not to trust our money solely to proprietary backup formats. Always have a backup of either the master private key in Wallet Import Format (WIF) or the seed-phrase/recovery-phrase/backup-phrase in BIP-39 format or in some equally well-defined and well-known public format

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