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Author Topic: 3 Man Offline Wallet Security  (Read 1096 times)
takagari (OP)
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December 10, 2013, 01:53:31 AM
 #1

Two friends and I are looking to invest on some BTC. We would like to have our returns go to an offline wallet we have with us.

But I'm wonderin, does anyone offer a way to take the wallet Key and split it into 3, requiring all three to ever open it again.

Would have for BTC to hit a million and one of us to move away quickly Wink

I guess we COULD simply break the string into 3, and each have 1/3 secured away. I've also seen an option that allows us to split it into 3, but only require two pieces to open the wallet, this may be the better option but sadly I can not find where this is done either.

Any help would be greatly appreciated guys! Thanks
Terk
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December 10, 2013, 02:07:50 AM
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Two friends and I are looking to invest on some BTC. We would like to have our returns go to an offline wallet we have with us.

But I'm wonderin, does anyone offer a way to take the wallet Key and split it into 3, requiring all three to ever open it again.

Read about m-of-n transactions, which are transactions that require at least M signatures out of N defined keys to spend their outputs. There's no three-click way to do this and you need to play with raw transactions. Here's an example of 2-of-3 which you can use to build 3-of-3: https://gist.github.com/gavinandresen/3966071

I wouldn't recommend 3-of-3 though. It's too easy for one of your friends to lose his private key or fall under a bus. Use 2-of-3 if you really need these funds to be controlled collectively. Whatever variant you choose, please exercise first using some small amount and try to spend it further from the m-of-n address. Make sure that you and your friends know how to do it.

Or simply split your returns as soon as they happen and let everyone has his own offline wallet. The simplest solutions are usually the best.

Gab1159
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December 10, 2013, 02:18:21 AM
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I don't understand why you just don't split the number of bitcoins bought between you three...Seems way more easier and less hassle to be had!
patricktim
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December 10, 2013, 02:20:05 AM
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sharing wallet is confusing for me. Sad

takagari (OP)
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December 10, 2013, 03:04:43 AM
 #5

We are mining a rig, and simply dumping said funds into the same wallet, likely over months. So we can later reinvest into a new mining rig, and withdraw initial investment.

Single wallet way easier. All three of us are military and work at the same location. So short of BTC hitting millions I'm not worried about one of us running off lol.

The 2 of 3 option does seem best! thank you for that. Icase something happens to one of us.

All three of us are invester's and would keep multiple copies of our key etc.
Not overly worried about that.

The M of N is perfect.

Edit:
Seems a bit different I'll need to spend time looking into how that is done exactly..
beckspace
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December 10, 2013, 03:26:56 AM
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Use Fragmented Backups - Armory.

In the field Required Fragments use 3.

In the field Total Fragments use 3 again.

Make a paper AND a file backup for each one of you. Then make copies. Protect them. Be careful, if you lose one of the three pieces, it's over. Two of then can't reconstruct the wallet.



https://bitcoinarmory.com/about/armory-backups-are-forever/

Edit:

I've also seen an option that allows us to split it into 3, but only require two pieces to open the wallet, this may be the better option but sadly I can not find where this is done either.

In that case, just use the default settings on Armory:

- Required Fragments 2

- Total Fragments 3
takagari (OP)
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December 10, 2013, 02:16:40 PM
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Thank you. That's exactly what we will do. I'll go buy a few new usb sticks. Hit them with trucrypt. As well as paper copies.

Thank you
kaito
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December 10, 2013, 03:22:12 PM
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Here's one method: http://en.wikipedia.org/wiki/Shamir's_Secret_Sharing

Alternatively, simply make the key to the wallet a combination of your 3 keys (and a nonce preferably).
E.g. wallet key = scrypt(scrypt(scrypt(nonce + keyA) + keyB) + keyC)
LiteCoinGuy
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December 10, 2013, 03:28:38 PM
 #9

Two friends and I are looking to invest on some BTC. We would like to have our returns go to an offline wallet we have with us.

But I'm wonderin, does anyone offer a way to take the wallet Key and split it into 3, requiring all three to ever open it again.



I wouldn't recommend 3-of-3 though. It's too easy for one of your friends to lose his private key or fall under a bus.


or steal it...who knows

 dont do that. keep your own wallet and you will still be friends in future.

btbrae
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December 10, 2013, 03:53:38 PM
 #10

Yeah, sooner or later your friends will go seperate ways and yeah, at first it will be all smiles and hugs "you hold the stash we're tight yo", then they get themselves bitcoin-pimp status cause they can't keep their mouth shut, fall for some girl that gets them hooked on crack and sells all their belongings for a fix, soon no home, no job, and before long they're breaking into your pad at 3am with a baseball bat screaming at your face to lead them on a wild goose chase around the neighbourhood trying to figure out where everybody put their m-of-n's.

I'd just split the coins...
FiatKiller
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December 10, 2013, 03:59:20 PM
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Just mine to an initial receiving wallet and then agree how often to send to each of your personal wallets. I agree to remove the complexity and interpersonal dynamics out of the equation.

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takagari (OP)
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December 11, 2013, 01:47:06 AM
 #12

Well these arn't exactly highschool friends. we are not overly concerned about hooker's, crack or disappearing. lol.

And WE don't plan on sharing a million dollar wallet, We plan to invest, collect, once our initial investment is in the wallet we cash that out. than decide how the rest is split/how often. the initial wallet would be for a month or two until the investment is returned.

I'm pretty sure they are fine with just me covering the wallet in reality, But I'd feel better and find it more fair to share it's key.

The 2 of 3 method is what I'll use. I'm in the process of finding an old server pc to setup as an offline wallet generator etc.

Thanks
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