.

[Ender985]

[readacted]

[1714910459]

1714910459

[1714910459]

1714910459

[btcven]

Say I create a new wallet in an offline computer, write down one receiving address and the public master key, save multiple copies of the seed under appropriate security measures, and then destroy said computer. I would then use the receiving address to send coins, and the wallet would serve as a cold storage. In order to spend those coins, I would install electrum in a different offline computer, restore my wallet from seed, then sign a spending transaction.

The strategy sounds good to me, since there is no need for maintaining a physical wallet on an offline computer waiting to get stolen/corrupted, each seed copy serves as a wallet backup, and an attacker could only steal the coins via obtaining a copy of the seed information and cracking all security measures in place to protect it. But maybe I'm overlooking a fatal flaw somewhere, you are welcome to try and steal my coins!

While researching the idea however, I came up with a couple of questions:

You'll need a lot of computers if you are going to destroy all of them after signing a transaction

I found out that in order to restore a wallet from seed, I need to connect to a server! If I cancel the connection process, a wallet is shown but it can not be used to sign offline transactions (it is probably showing an unrelated newly created wallet, not sure). I don't see the need for internet connection while restoring from seed, and I'd argue it's a bad idea since exposing a machine to the internet is potentially hazardous. Is this an intended/necessary feature, or will this problem be solved in an upcoming electrum version?

You don't need to be online for restoring. Try using the -o or --offline in Terminal

I've read that in Electrum's version 2.0, the generated seed will change from the current 12 words long to a longer one. Will this conflict in any way with my ability to restore a 12-word seeded wallet? I intended to save multiple copies of the electrum version used to generate the cold wallet, to be able to restore the wallet independently of the project's future developments. But since electrum depends on the online servers it's not a fully stand-alone program, and I am a bit worried of what would happen in the case of divergent developments or in case the project gets abandoned.

Thanks!

The current 12 words seed will be supported in 2.0

Again, servers are only needed to get balance and broadcast transactions. You can always generate your private keys offline, you only need a copy of the application.

[btcven]

Thanks for confirming the 12 seed will be backwards compatible with the newer versions of electrum, it makes sense but I wanted to make sure. However I have to ask, why is it that they're changing the seed length? Is it that the current seed is not secure enough?

It will be supported in 2.0 for backward compatibility. This new version will introduce BIP32 and the seed version will be encoded in the seed too, that's the reason it will be larger. This way future versions of the software will know what seed it is dealing with without needing the user to find it out himself.

[Abdussamad]

I've read that in Electrum's version 2.0, the generated seed will change from the current 12 words long to a longer one. Will this conflict in any way with my ability to restore a 12-word seeded wallet? I intended to save multiple copies of the electrum version used to generate the cold wallet, to be able to restore the wallet independently of the project's future developments. But since electrum depends on the online servers it's not a fully stand-alone program, and I am a bit worried of what would happen in the case of divergent developments or in case the project gets abandoned.

Thanks!

You need the private keys of your bitcoin addresses to spend your coins. To get the private keys you need at the very least two things:

1. The seed
2. The algorithm to generate addresses and private keys from a seed.

1 you already have.

2 is out "there" on the Internet in many, many forms. For example electrum has its own github repo that has all versions of electrum since they started using github. It's just a matter of finding the right version. There are also a bunch of other projects that can generate private keys using an electrum seed. sx and vbuterin's pybitcointools come to mind.

If you are really worried about 2 you can create your own backup of electrum. Just copy the download file onto a USB stick or DVD. Then you won't have to depend on anyone else.

[PeFro]

I´ve been trying to do exactly what OP is refering to.

I´ve started Electrum with the -o option and successfully restored from a previously created seed.
When I try to sign an unsigned transaction created on my online computer, I get an Exception "Adress not found" showing the public key adress which is the input for that transaction.

That public key adress isn´t showing up on the offline computer but I would assume that it could be derived from one of the private keys!?

What am I missing?

edit:

nevermind, found it:

executing "wallet.accounts[0].create_new_address(0)" in the console did the trick... described here https://bitcointalk.org/index.php?topic=344115.0