Comments on: My GnuPG Locality Problem http://pthree.org/2007/02/19/my-gnupg-locality-problem/ Linux. GNU. Freedom. Wed, 08 Feb 2012 02:59:26 +0000 hourly 1 http://wordpress.org/?v=3.4-alpha By: Elliot Murphy 28:1 » Blog Archive » links for 2007-03-09 http://pthree.org/2007/02/19/my-gnupg-locality-problem/#comment-37251 Elliot Murphy 28:1 » Blog Archive » links for 2007-03-09 Fri, 09 Mar 2007 23:21:20 +0000 http://www.pthree.org/2007/02/19/my-gnupg-locality-problem/#comment-37251 [...] Aaron Toponce » Blog Archive » My GnuPG Locality Problem interesting discussion on how to handle GPG keys from multiple locations while maintaining security [...] [...] Aaron Toponce » Blog Archive » My GnuPG Locality Problem interesting discussion on how to handle GPG keys from multiple locations while maintaining security [...]

]]> By: Ubuntu | Aaron Toponce: My GnuPG Locality Solution http://pthree.org/2007/02/19/my-gnupg-locality-problem/#comment-33458 Ubuntu | Aaron Toponce: My GnuPG Locality Solution Tue, 20 Feb 2007 23:45:24 +0000 http://www.pthree.org/2007/02/19/my-gnupg-locality-problem/#comment-33458 [...] I provided a problem about how to use my GnuPG key regardless of my location. In reality, there are only 3 computers [...] [...] I provided a problem about how to use my GnuPG key regardless of my location. In reality, there are only 3 computers [...]

]]> By: Aaron Toponce » Blog Archive » My GnuPG Locality Solution http://pthree.org/2007/02/19/my-gnupg-locality-problem/#comment-33447 Aaron Toponce » Blog Archive » My GnuPG Locality Solution Tue, 20 Feb 2007 22:16:06 +0000 http://www.pthree.org/2007/02/19/my-gnupg-locality-problem/#comment-33447 [...] you're new here, you may want to subscribe to my RSS feed. Thanks for visiting!Yesterday, I provided a problem about how to use my GnuPG key regardless of my location. In reality, there are only 3 computers [...] [...] you’re new here, you may want to subscribe to my RSS feed. Thanks for visiting!Yesterday, I provided a problem about how to use my GnuPG key regardless of my location. In reality, there are only 3 computers [...]

]]> By: Aaron http://pthree.org/2007/02/19/my-gnupg-locality-problem/#comment-33418 Aaron Tue, 20 Feb 2007 16:40:11 +0000 http://www.pthree.org/2007/02/19/my-gnupg-locality-problem/#comment-33418 I have to admit that libgfshare is superior to the solution that I came up with. Splitting up the key, and having the ability to recreate it is nice, no doubt. However, I'm still proud of what I thought of, so I'll be interested in what others think come here in about 6 hours. I have to admit that libgfshare is superior to the solution that I came up with. Splitting up the key, and having the ability to recreate it is nice, no doubt.

However, I’m still proud of what I thought of, so I’ll be interested in what others think come here in about 6 hours.

]]> By: Soren Hansen http://pthree.org/2007/02/19/my-gnupg-locality-problem/#comment-33414 Soren Hansen Tue, 20 Feb 2007 16:16:38 +0000 http://www.pthree.org/2007/02/19/my-gnupg-locality-problem/#comment-33414 Typical. I started writing my comment, went to a lecture, came back and finished it, sent it and in the meanwhile, Daniel Silverstone has told you about libgfshare himself. Oh well.. :-) Typical. I started writing my comment, went to a lecture, came back and finished it, sent it and in the meanwhile, Daniel Silverstone has told you about libgfshare himself. Oh well.. :-)

]]> By: Soren Hansen http://pthree.org/2007/02/19/my-gnupg-locality-problem/#comment-33410 Soren Hansen Tue, 20 Feb 2007 15:50:23 +0000 http://www.pthree.org/2007/02/19/my-gnupg-locality-problem/#comment-33410 You're looking for libgfshare. It's based on Adi Shamir's Secret Sharing algorithm (Shamir put the S in RSA). It allows you take a confidential piece of data and generate n pieces of data where any m of these n pieces are required to reassemble the original data. Say you have a USB key, a laptop machine and a desktop machine. You can then split up your GPG key into three parts, requiring two parts to reassemble. You put a part on each of the USB, laptop and desktop. Whenever you need your GPG key, you plug in the USB stick and have your GPG key assembled. When you remove the USB stick, the assembled key could be deleted. If your USB stick is stolen, the thief will have a useless piece of data and you will still have two pieces left (one on your laptop and one on your desktop) and will be able to reassemble the GPG key and create a new share set. libgfshare was developed by Daniel Silverstone, is free software (an MIT-like license) and can be found here: http://www.digital-scurf.org/software/libgfshare and in the libgfshare{1,-bin} packages in Ubuntu. I've created a desktop daemon thing that listens for plugin events from hal waiting for a USB stick to be inserted and when that happens it searches for pieces that can be used to reconstruct certain files. It also takes care of deleting assembled file again when the USB stick is removed. It was my first python project so it's probably ugly as ****, so I'll have to clean it up a bit before I release it, but until then you can just use libgfshare as it is (there are binaries included). Have fun! You’re looking for libgfshare. It’s based on Adi Shamir’s Secret Sharing algorithm (Shamir put the S in RSA). It allows you take a confidential piece of data and generate n pieces of data where any m of these n pieces are required to reassemble the original data.

Say you have a USB key, a laptop machine and a desktop machine.

You can then split up your GPG key into three parts, requiring two parts to reassemble. You put a part on each of the USB, laptop and desktop.

Whenever you need your GPG key, you plug in the USB stick and have your GPG key assembled. When you remove the USB stick, the assembled key could be deleted.

If your USB stick is stolen, the thief will have a useless piece of data and you will still have two pieces left (one on your laptop and one on your desktop) and will be able to reassemble the GPG key and create a new share set.

libgfshare was developed by Daniel Silverstone, is free software (an MIT-like license) and can be found here: http://www.digital-scurf.org/software/libgfshare
and in the libgfshare{1,-bin} packages in Ubuntu.

I’ve created a desktop daemon thing that listens for plugin events from hal waiting for a USB stick to be inserted and when that happens it searches for pieces that can be used to reconstruct certain files. It also takes care of deleting assembled file again when the USB stick is removed. It was my first python project so it’s probably ugly as ****, so I’ll have to clean it up a bit before I release it, but until then you can just use libgfshare as it is (there are binaries included).

Have fun!

]]> By: Tobias Rapp http://pthree.org/2007/02/19/my-gnupg-locality-problem/#comment-33409 Tobias Rapp Tue, 20 Feb 2007 15:29:55 +0000 http://www.pthree.org/2007/02/19/my-gnupg-locality-problem/#comment-33409 @Aaron: You should not need to generate a new key (although generating sub-keys of your main key on the smartcard is preferred in the HowTos). To move the existing key to the card one might call: <code>$ gpg --edit-key 0x12345678</code> and then do a <code>command> keytocard</code> But I must admit that I have not tested that procedure personally. You can buy a smartcard at <a href="http://www.kernelconcepts.de/products/security-en.shtml" rel="nofollow">Kernel Concepts</a>. They also sell card readers. But if you have a lot of computers and do not want to take a USB reader with you all the time this solution can get expensive, I agree. I use my smartcard on just two computers (home, work) so that was no big problem... @Aaron:

You should not need to generate a new key (although generating sub-keys of your main key on the smartcard is preferred in the HowTos). To move the existing key to the card one might call:

1
$ gpg --edit-key 0x12345678

and then do a

1
command&gt; keytocard

But I must admit that I have not tested that procedure personally.

You can buy a smartcard at Kernel Concepts. They also sell card readers. But if you have a lot of computers and do not want to take a USB reader with you all the time this solution can get expensive, I agree. I use my smartcard on just two computers (home, work) so that was no big problem…

]]> By: Daniel Silverstone http://pthree.org/2007/02/19/my-gnupg-locality-problem/#comment-33405 Daniel Silverstone Tue, 20 Feb 2007 14:46:09 +0000 http://www.pthree.org/2007/02/19/my-gnupg-locality-problem/#comment-33405 I sat down, thought about the problem, and then researched crypto which would help. Clearly the concerns about losing your USB key with your GPG keys on it are valid. So here's my solution 1. Using a little python and tmpfs magic, make it so that when you plug your thumbdrive into your machine it runs a script to prepare your gpg key and put it in the tmpfs. 2. Using GFShare (a library and toolset I wrote) split your key into 'secret shares' which are then distributed around your computer, laptop and usb key. 3. Profit (or be secure, or something) As a reference, I keep my GPG keys as a three-of-five split. One share on my desktop, one on my laptop, one on my home server, two on the usb drive. That way, the usb drive plus any of m y machines lets me at my key, but if I lose the thumbdrive, the thief gets nothing and I can reconstruct my key with my three computers and then make a fresh set of shares, deleting the old ones to ensure the compromise cannot occur with the lost shares. My website carries the GFShare software along with a lot of the maths explained. The codebase carries a lovely paper written in LaTeX which explains the maths behind it and goes on to prove that it's all right. I hope your solution is as effective as this, otherwise, perhaps you should consider something like this :-) Naturally, if your idea is more clever then I'd love to know it so I'll be looking again tomorrow. I sat down, thought about the problem, and then researched crypto which would help.

Clearly the concerns about losing your USB key with your GPG keys on it are valid. So here’s my solution

1. Using a little python and tmpfs magic, make it so that when you plug your thumbdrive into your machine it runs a script to prepare your gpg key and put it in the tmpfs.

2. Using GFShare (a library and toolset I wrote) split your key into ‘secret shares’ which are then distributed around your computer, laptop and usb key.

3. Profit (or be secure, or something)

As a reference, I keep my GPG keys as a three-of-five split. One share on my desktop, one on my laptop, one on my home server, two on the usb drive.

That way, the usb drive plus any of m y machines lets me at my key, but if I lose the thumbdrive, the thief gets nothing and I can reconstruct my key with my three computers and then make a fresh set of shares, deleting the old ones to ensure the compromise cannot occur with the lost shares.

My website carries the GFShare software along with a lot of the maths explained. The codebase carries a lovely paper written in LaTeX which explains the maths behind it and goes on to prove that it’s all right.

I hope your solution is as effective as this, otherwise, perhaps you should consider something like this :-) Naturally, if your idea is more clever then I’d love to know it so I’ll be looking again tomorrow.

]]> By: Aaron http://pthree.org/2007/02/19/my-gnupg-locality-problem/#comment-33402 Aaron Tue, 20 Feb 2007 14:21:20 +0000 http://www.pthree.org/2007/02/19/my-gnupg-locality-problem/#comment-33402 Tobias: A smart card is a perfect solution. However, I don't want to use another key, but rather, just use my own. I don't know if this is possible with the smart card or not. Also, can I get a smart card without joining an organization? Tobias:

A smart card is a perfect solution. However, I don’t want to use another key, but rather, just use my own. I don’t know if this is possible with the smart card or not. Also, can I get a smart card without joining an organization?

]]> By: Matthew East http://pthree.org/2007/02/19/my-gnupg-locality-problem/#comment-33388 Matthew East Tue, 20 Feb 2007 13:44:58 +0000 http://www.pthree.org/2007/02/19/my-gnupg-locality-problem/#comment-33388 Webmail over https? Webmail over https?

]]> By: Jonas http://pthree.org/2007/02/19/my-gnupg-locality-problem/#comment-33371 Jonas Tue, 20 Feb 2007 11:43:33 +0000 http://www.pthree.org/2007/02/19/my-gnupg-locality-problem/#comment-33371 Tobias: How many computers include a smart card reader though? Tobias:

How many computers include a smart card reader though?

]]> By: Tobias Rapp http://pthree.org/2007/02/19/my-gnupg-locality-problem/#comment-33369 Tobias Rapp Tue, 20 Feb 2007 11:38:33 +0000 http://www.pthree.org/2007/02/19/my-gnupg-locality-problem/#comment-33369 A cite from the <a href="http://www.gnupg.org/howtos/card-howto/en/smartcard-howto.html" rel="nofollow">GnuPG Card HowTo</a>: <blockquote>To work with GnuPG on different machines (private PC, at work, with laptop etc.) the secret key has to be present on every machine. Distributing the secret key to a lot of different machines does not support its secrecy. Especially at work where other people have root access on your machine it is not save to store your secret key. Starting with version 1.3.3 GnuPG supports smart cards to save your keys.</blockquote> When using a smartcard your private key will not leave the card. Thus it is perfectly suited for your needs. So if you live in Europe just become a member of the <a href="http://www.fsfe.org/" rel="nofollow">FSF Europe Fellowship</a> and you will get such a nice smartcard to protect your privacy :-) Else you might fetch an OpenPGP compatible card from some online store. A cite from the GnuPG Card HowTo:

To work with GnuPG on different machines (private PC, at work, with laptop etc.) the secret key has to be present on every machine. Distributing the secret key to a lot of different machines does not support its secrecy. Especially at work where other people have root access on your machine it is not save to store your secret key. Starting with version 1.3.3 GnuPG supports smart cards to save your keys.

When using a smartcard your private key will not leave the card. Thus it is perfectly suited for your needs.

So if you live in Europe just become a member of the FSF Europe Fellowship and you will get such a nice smartcard to protect your privacy :-)

Else you might fetch an OpenPGP compatible card from some online store.

]]> By: Marius Gedminas http://pthree.org/2007/02/19/my-gnupg-locality-problem/#comment-33365 Marius Gedminas Tue, 20 Feb 2007 10:47:56 +0000 http://www.pthree.org/2007/02/19/my-gnupg-locality-problem/#comment-33365 I wonder if you can write a gpg wrapper that actually sshs into your server and runs gpg there. Might be tricky when there are extra file descriptors used for passphrase input from GUI apps, but ought to be doable somehow. I use ssh + mutt personally. I wonder if you can write a gpg wrapper that actually sshs into your server and runs gpg there. Might be tricky when there are extra file descriptors used for passphrase input from GUI apps, but ought to be doable somehow.

I use ssh + mutt personally.

]]> By: Andreas Olsson http://pthree.org/2007/02/19/my-gnupg-locality-problem/#comment-33346 Andreas Olsson Tue, 20 Feb 2007 08:59:28 +0000 http://www.pthree.org/2007/02/19/my-gnupg-locality-problem/#comment-33346 Myself I mount my homeserver:~./gnupg using sshfs. Well, it is not something I I'd do from any computer, but from some which I at least kind of trust. Myself I mount my homeserver:~./gnupg using sshfs. Well, it is not something I I’d do from any computer, but from some which I at least kind of trust.

]]> By: bob http://pthree.org/2007/02/19/my-gnupg-locality-problem/#comment-33322 bob Tue, 20 Feb 2007 05:07:21 +0000 http://www.pthree.org/2007/02/19/my-gnupg-locality-problem/#comment-33322 I agree with Hans. Mutt/screen/ssh I agree with Hans. Mutt/screen/ssh

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