I know I must be getting some basic idea wrong, so I'd like you to explain to me: If I have for example Mist wallet installed on multiple computers that are connected to the internet, all with the same account, and also I moved the wallet file to a Ledger USB drive, how does it protect me from unwanted transactions? I understand that from the Ledger itself it cannot be stolen, but the same wallet file is connected to the internet in other computers, so how can it protect?
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a ledger isn't a USB drive. A ledger generates it's mnemonic on it's own and stores it locally. You can't copy the file from the ledger, as then you mine as well use a $1 usb drive. The computer sends the transaction to the ledger for it to sign.– natewelch_Commented Nov 26, 2017 at 18:42
1 Answer
Keeping backups of your private keys (and their passwords) is a good idea. You should know exactly where those backups are, and who has access to them.
If I have for example Mist wallet installed on multiple computers that are connected to the internet, all with the same account,
To me, that doesn't sound like a backup strategy. You've effectively multiplied the attack surface for anyone wanting to get their grubby hands on your keys. Do you know exactly which computers have which keys? Do you know that all of those computers are connected to the internet in the same secure way? Are they all running the latest security patches (hardware and software)? And so on.
and also I moved the wallet file to a Ledger USB drive,
This is generally a good way to keep your keys safe. Keep this, and the 24-word mnemonic safe.
(Also see: What is the recommended way to safely store Ether?)
how does it protect me from unwanted transactions?
If someone has access to your machines, and they know your account passwords (e.g. from keyloggers), your strategy doesn't. The more computers you spread your keys across, the more targets you've presented to the world.
I understand that from the Ledger itself it cannot be stolen
It can be physically stolen, and so can the bit of paper you've written your mnemonic on.
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That didn't answer my question, because I knew all of that information.What I don't understand is, if you use the same account on all devices, doesn't it mean that it's the same key and password? Only putting the file on a different device? Or you're saying that you can flag your account as "active" only on a single device from 1 account? Commented Nov 26, 2017 at 13:11
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Or youre saying I need to copy the file to multiple OFFLINE devices, and use only the ledger to deposit/withdrawal? Commented Nov 26, 2017 at 13:37
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Ok, thanks for clarifying what you were asking. Yes, if you want to use the same account on different computers you would need to copy the private key to those computers (the address is derived from the key), which means that key/address is potentially less secure. (You would use the same password for each instance of the same key.) Multiple offline devices would be safer, yes. You could then, as you say, use the Ledger, via the Ledger browser app, for sending/receiving. Commented Nov 26, 2017 at 18:40
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BUT you can't back-up existing keyfiles to the Ledger - it will create a new one for you. The 24-word mnemonic is then the thing you need to keep safe, not a keyfile. Commented Nov 26, 2017 at 18:41
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Thank you, now I got it, at first I thought Ledger was a regular USB where you transfer files in and out, but with a password in order to be able to use it. I didn't realize it's completely different and creates your own address there, thank you! Commented Nov 26, 2017 at 19:36