I think you mean "any four of the eleven".
Indeed. Fixed.
Topic: Is anyone working on / has implemented a “two-factor paper wallet”? (Read 4206 times)
September 07, 2012, 04:16:01 AM
Indeed. Fixed.
September 05, 2012, 05:50:11 AM
If you have a 8-of-11 split, then if any three of the eleven parts are lost you lose access to the key.
I think you mean "any four of the eleven". September 05, 2012, 05:10:43 AM
Does this mean if either part is lost, you lose access to any coins in there?
If you have a 1-of-2 split, then either part is fine to get you the key.
If you have a 4-of-5 split, then if any two of the five parts are lost you lose access to the key.
If you have a 8-of-11 split, then if any four of the eleven parts are lost you lose access to the key.
Also, there's a new thread now: https://bitcointalksearch.org/topic/m.1139496
legendary
Activity: 1862
Merit: 1011
Reverse engineer from time to time
September 04, 2012, 01:24:38 PM
Does this mean if either part is lost, you lose access to any coins in there?
August 13, 2012, 08:58:32 PM
So, here's my current version of the Python utility:
https://www.dropbox.com/sh/ysbyb3v5zec43pe/Emrn5v2slX/files.zip
The one thing I can't figure out is what it exactly means to take the "SHA256(resulting bitcoin address)". Do I SHA256 the address itself? A bytestring version of it? A bytestring version padded with '\x00'? None of those seems to work. But barring that my utility is decoding Casascius's example correctly.
Another question/concern: why limit it to (8,8)? There is no need whatsoever to do this. All you have to do is keep applying progressively smaller caps to the high-position intermediate k-values and as long as the cap keeps decreasing fast enough there's no problem - I implemented it in my code already. We can limit it to (16,16) and have 8 bytes of error correction in the encoding instead of 9 and everything will work just fine.
https://www.dropbox.com/sh/ysbyb3v5zec43pe/Emrn5v2slX/files.zip
The one thing I can't figure out is what it exactly means to take the "SHA256(resulting bitcoin address)". Do I SHA256 the address itself? A bytestring version of it? A bytestring version padded with '\x00'? None of those seems to work. But barring that my utility is decoding Casascius's example correctly.
Another question/concern: why limit it to (8,8)? There is no need whatsoever to do this. All you have to do is keep applying progressively smaller caps to the high-position intermediate k-values and as long as the cap keeps decreasing fast enough there's no problem - I implemented it in my code already. We can limit it to (16,16) and have 8 bytes of error correction in the encoding instead of 9 and everything will work just fine.
August 10, 2012, 09:12:54 AM
for example, solving m-of-n yields 1 bitcoin address. But practical use of the scheme might be an "in-case-I-die" safety measure
When I read halfway down the first page I realised it was exactly what I needed. I've been thinking about the idea of having a private key to some GPG encrypted information stored in such a way that you only need say 3/5 keys to decrypt the information. That way, you can communicate from inside an absolutely sealed environment and save things like passwords or details of assets and projects and particularly bitcoins, and save all that information with a measure of security but entirely outside of your control. By holding on to one of the keys yourself, perhaps a crucial key, you could ensure nothing could happen while you were alive. I want to experiment with a 2-tiered system, as in you need [3/5 root keys], or [2/5 root and ANY 3 of like 8 secondary keys]; that is that the secondary keys are not particular to the lost root keys.
Anyway, don't mind me.
Subbed.
Sure, all you need to do for that is to set up a (3,6) system where one of the six outputs is itself stored in the form of a (3,8) system.
August 10, 2012, 12:42:32 AM
Is this the same math as Shamir Secret Sharing (using polynomials) or something different? I've used that before to encode my password safe in several places and I'm sure it would work easily for keys too.
August 09, 2012, 09:25:38 AM
for example, solving m-of-n yields 1 bitcoin address. But practical use of the scheme might be an "in-case-I-die" safety measure
When I read halfway down the first page I realised it was exactly what I needed. I've been thinking about the idea of having a private key to some GPG encrypted information stored in such a way that you only need say 3/5 keys to decrypt the information. That way, you can communicate from inside an absolutely sealed environment and save things like passwords or details of assets and projects and particularly bitcoins, and save all that information with a measure of security but entirely outside of your control. By holding on to one of the keys yourself, perhaps a crucial key, you could ensure nothing could happen while you were alive. I want to experiment with a 2-tiered system, as in you need [3/5 root keys], or [2/5 root and ANY 3 of like 8 secondary keys]; that is that the secondary keys are not particular to the lost root keys.
Anyway, don't mind me.
Subbed.
August 08, 2012, 07:40:35 AM
Hello,
I'm working on a "traditional" two factor wallet, called SmartCardWallet. In essence you shall have a physical card in your wallet, that acts something like a normal chipped visa card. Unlike paper based solutions, it is considered a difficult task for an average adversary to copy/attack the contents of a smart card. See https://bitcointalksearch.org/topic/smart-card-wallet-take-2-94119
I just created this wiki page.
I'm coining the term here, I think ... not sure what was it called when discussed on Bitcointalk.
My question is: Has anyone implemented this "2 factor paper wallet"? Is it being worked on?
x-post to SE
Maybe relevant:I'm coining the term here, I think ... not sure what was it called when discussed on Bitcointalk.
My question is: Has anyone implemented this "2 factor paper wallet"? Is it being worked on?
x-post to SE
I'm working on a "traditional" two factor wallet, called SmartCardWallet. In essence you shall have a physical card in your wallet, that acts something like a normal chipped visa card. Unlike paper based solutions, it is considered a difficult task for an average adversary to copy/attack the contents of a smart card. See https://bitcointalksearch.org/topic/smart-card-wallet-take-2-94119
August 07, 2012, 11:49:32 PM
These m-of-n transactions (when nested) are starting to look like discrete components and Bitcoin is the energy. Combining different types of transactions could create logic gates of money. The circuit would be traceable by the blockchain, though it would create a lot of transactions. That's something to worry about later. I'm thinking that this could be a way to create community based lending systems that amplify funds for borrowers that meet the criteria of key persons in the circuit. There would be many different functions for different amounts depending on the setup, enough to meet the needs of borrowers of all sorts. Thoughts, or should I just start drinking?
August 07, 2012, 06:31:28 PM
Now that I have it working, I am thinking of how it could evolve a bit:
for example, solving m-of-n yields 1 bitcoin address. But practical use of the scheme might be an "in-case-I-die" safety measure, and I am thinking the keys ought to contain a field to say how many addresses are intended to be used (using the sum as a deterministic wallet seed).
For example if I am going to go to the effort of passing out around key parts, it's going to be a real pain in the ass each time I need to discard the address I'm using, so it would be better if when my loved ones went to restore my coins, the restore utility would know, "aha! this yields 24 addresses" and prints out 3 pages of paper wallets with 8 addresses per page.
for example, solving m-of-n yields 1 bitcoin address. But practical use of the scheme might be an "in-case-I-die" safety measure, and I am thinking the keys ought to contain a field to say how many addresses are intended to be used (using the sum as a deterministic wallet seed).
For example if I am going to go to the effort of passing out around key parts, it's going to be a real pain in the ass each time I need to discard the address I'm using, so it would be better if when my loved ones went to restore my coins, the restore utility would know, "aha! this yields 24 addresses" and prints out 3 pages of paper wallets with 8 addresses per page.
You could use a key family scheme to generate as many addresses as you want from a single seed - something like this:
http://crypto.stackexchange.com/questions/1534/families-of-public-private-keys-in-elliptic-curve-cryptography
It also has the advantage that you could store some derivative privkeys in a more accessible place (eg. desktop client, blockchain.info) and use them normally without risking your root key being compromised.
August 07, 2012, 09:58:11 AM
The output from several randomly generated k-of-n keys could be the inputs of user defined m-of-n transactions.
August 07, 2012, 09:51:25 AM
Now that I have it working, I am thinking of how it could evolve a bit:
for example, solving m-of-n yields 1 bitcoin address. But practical use of the scheme might be an "in-case-I-die" safety measure, and I am thinking the keys ought to contain a field to say how many addresses are intended to be used (using the sum as a deterministic wallet seed).
For example if I am going to go to the effort of passing out around key parts, it's going to be a real pain in the ass each time I need to discard the address I'm using, so it would be better if when my loved ones went to restore my coins, the restore utility would know, "aha! this yields 24 addresses" and prints out 3 pages of paper wallets with 8 addresses per page.
for example, solving m-of-n yields 1 bitcoin address. But practical use of the scheme might be an "in-case-I-die" safety measure, and I am thinking the keys ought to contain a field to say how many addresses are intended to be used (using the sum as a deterministic wallet seed).
For example if I am going to go to the effort of passing out around key parts, it's going to be a real pain in the ass each time I need to discard the address I'm using, so it would be better if when my loved ones went to restore my coins, the restore utility would know, "aha! this yields 24 addresses" and prints out 3 pages of paper wallets with 8 addresses per page.
August 07, 2012, 09:20:04 AM
OK, I have baked the M-of-N wallet code into my Casascius Bitcoin Utility, just as a proof of concept. The M-of-N calc is under "Tools".
Source and binaries are included in this ZIP file. This is for Windows.
https://www.casascius.com/BtcAddressMN.zip
This won't yet print any M-of-N paper wallets - it will simply produce the M-of-N codes (which you can copy and paste away), and recombine any M of them back into a regular private key (if you copy and paste them back in). It could probably use a lot of scrutiny and testing, but it seems to work like it should.
Source and binaries are included in this ZIP file. This is for Windows.
https://www.casascius.com/BtcAddressMN.zip
This won't yet print any M-of-N paper wallets - it will simply produce the M-of-N codes (which you can copy and paste away), and recombine any M of them back into a regular private key (if you copy and paste them back in). It could probably use a lot of scrutiny and testing, but it seems to work like it should.
Nice!
I'll come up with a cross-platform python utility for this when I have time.
August 07, 2012, 08:38:14 AM
OK, I have baked the M-of-N wallet code into my Casascius Bitcoin Utility, just as a proof of concept. The M-of-N calc is under "Tools".
Source and binaries are included in this ZIP file. This is for Windows.
https://www.casascius.com/BtcAddressMN.zip
This won't yet print any M-of-N paper wallets - it will simply produce the M-of-N codes (which you can copy and paste away), and recombine any M of them back into a regular private key (if you copy and paste them back in). It could probably use a lot of scrutiny and testing, but it seems to work like it should.
Source and binaries are included in this ZIP file. This is for Windows.
https://www.casascius.com/BtcAddressMN.zip
This won't yet print any M-of-N paper wallets - it will simply produce the M-of-N codes (which you can copy and paste away), and recombine any M of them back into a regular private key (if you copy and paste them back in). It could probably use a lot of scrutiny and testing, but it seems to work like it should.
Nice!
I'll come up with a cross-platform python utility for this when I have time.
August 06, 2012, 08:12:40 PM
OK, I have baked the M-of-N wallet code into my Casascius Bitcoin Utility, just as a proof of concept. The M-of-N calc is under "Tools".
Source and binaries are included in this ZIP file. This is for Windows.
https://www.casascius.com/BtcAddressMN.zip
This won't yet print any M-of-N paper wallets - it will simply produce the M-of-N codes (which you can copy and paste away), and recombine any M of them back into a regular private key (if you copy and paste them back in). It could probably use a lot of scrutiny and testing, but it seems to work like it should.
Source and binaries are included in this ZIP file. This is for Windows.
https://www.casascius.com/BtcAddressMN.zip
This won't yet print any M-of-N paper wallets - it will simply produce the M-of-N codes (which you can copy and paste away), and recombine any M of them back into a regular private key (if you copy and paste them back in). It could probably use a lot of scrutiny and testing, but it seems to work like it should.
August 06, 2012, 03:21:45 PM
With a scheme like this, is it possible to create an interdependence of keys where a community has keys that overlap within and between groups? For instance, an apartment building where everyone needs keys from their next door neighbors with 3 of 5 so either side or two on the same side will do. This would create an interdependent web. If this works, it would make for some interesting banking schemes.
August 06, 2012, 12:12:03 PM
1 - the ability to put your key in 2 different geographically separate places to protect them from snooping/theft. example, I might put one half in my safety deposit box and keep the other half at home, so someone from the bank who happens to gain access to my safety deposit box doesn't get my bitcoins.
That can be done much simpler ways. For example, you can literally separate the key bits in half. You can also generate a random sequence the same length as the key, and store that along with the key XORed with that.Quote
2 - the ability to have 2 separate machines generate a single key, so even if one or both machines is compromised, the resulting key is not. (Example: Smartphone + Computer). All that matters is that both machines aren't compromised by the same person or someone with the ability to access both halves.
Any scheme that doesn't involve storing the private key on a single device has this property.simple and freaking ingenious, Im sold
edit: pull out a pair of scissors ffs and problem solved
August 06, 2012, 11:09:38 AM
Math isn't my strong suit. Let me get this straight:
m-of-n is when m=n-1
K-of-N is when k=n-2
m-of-n and k-of-n are the same... differing only by a letter which was arbitrarily chosen. the only difference is the first proposal I wrote required that m be n-1 (the letters themselves don't matter)... the proposal that Vitalik wrote (which I coded and seems to work) allows m to be as low as 1 and as much as n. If you substitute k for n, everything is the same, you have merely changed the letter.
August 06, 2012, 04:51:51 AM
Would you be willing to write your suggestion up on the wiki and assume that your reader doesn't understand the math? For example, when you say "find n values that meet the following conditions", it's not obvious to me how one would go about finding such a value.
https://en.bitcoin.it/wiki/User:Vbuterin/K_of_N_redundant_offline_private_key_proposal
Fairly technical (hard to avoid that when describing these types of protocols), but here you go.
m-of-n is when m=n-1
K-of-N is when k=n-2
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