9 ms·

Good solid set of tips. One thing I would like to see a summary of is the use of secure USB-keys to keep your private key off your computing device using the s

Good solid set of tips. One thing I would like to see a summary of is the use of secure USB-keys to keep your private key off your computing device using the smart-card functionality in GnuPG [0]. It seems that this is possible with devices such as Yubico's Yubikey Neo [1]. Having your GPG private key with you as a physical 'key' — with all private operations performed via the USB-key — seems like a great way to increase security and prevent loss of your private key. [0]: https://en.wikipedia.org/wiki/OpenPGP_card https://en.wikipedia.org/wiki/OpenPGP_card [1]: https://developers.yubico.com/PGP/Importing_keys.html https://developers.yubico.com/PGP/Importing_keys.html

dimastopel 11y ago
What happens if you lose the card / key, or in case it becomes non-functional? How do you back-up the private key?
- nickik 11y ago
  Maybe read this post of mine: https://news.ycombinator.com/item?id=11437413 https://news.ycombinator.com/item?id=11437413
  - dimastopel 11y ago
    Indeed, didn't think about having another stick for the backup.
nickik 11y ago
Yes. I use a Yubikey 4 Nano and I have it always plugged in to may Laptop. The Master key however is not on the Yubikey. It is only available on external encrpyted USB drive that I only use for certification. Currently their is no way to use your 4096bit key over NFC. The Yubikey NEO only supports 2048bit keys and the Yubikey 4 does not support NFC. So you have to either use a secondary key or expose yourself and put your private key on your phone. I fully expect Yubico to realease a Yubikey 4 with NFC sometime this year, and this would enable my optimal solution: I have a Smartphone and a Laptop. To securly use them, I should have 3 Yubikeys, 1 of them a Nano plus 2 USB Sticks. The Nano is always plugged into my laptop, exept for exeptional situations. One of the large Yubikeys is on my keyring, the other is at home as a backup. One USB stick is only for the Master Key and I would bring it along if I expected to use certification. The other USB Stick is a poor backup and savly stored at home, it also contains the Revocation Key. All this is pretty expensive and not really all that easy to set up but if you do it you have the great benefits, like ähh well äähh I guess other crypto nerds might think its cool.
- Freak_NL 11y ago
  Nice set up. It's all about proportionality. If your GPG-key (and SSH-key) grants you access to servers containing sensitive data placed there in good faith (think medical records), then having your private keys stored somewhere they can't be copied from without physically obtaining (and destroying) the keys is totally justified. And if you are doing it because, well, you can, then you are helping in making this knowledge available to the wider community.
  - nickik 11y ago
    I have not jet transitioned to using SSH-keys from the Yubikey. I have some issues with the ssh-agent understanding that I use a PIV interface. I think pushing the bounds and evaluating usablity, maybe finding bugs is important. I still mostly do it for fun. I really like thinking threw different thread models and security systems. For example, compare the security gained by keybases new system (NaCL, device keys, tracking) with my old gpg/smartcard/wot system.
- hollander 11y ago
  Yubico themselve say that the 4096 bit key only adds 16% more security. So the Neo is practically as safe as the 4. https://www.yubico.com/2015/02/big-debate-2048-4096-yubicos-stand/ https://www.yubico.com/2015/02/big-debate-2048-4096-yubicos-... > While it is true that a longer key provides better security, we have shown that by doubling the length of the key from 2048 to 4096, the increase in bits of security is only 18, a mere 16%. Moreover, besides requiring more storage, longer keys also translate into increased CPU usage and higher power consumption.
  - schlowmo 11y ago
    The math behind the security gain by increasing the key length of an RSA key seems slighly more complicated then one might expect. Here is a (short) introduction by the GnuPG folks: https://www.gnupg.org/faq/gnupg-faq.html#no_default_of_rsa4096 https://www.gnupg.org/faq/gnupg-faq.html#no_default_of_rsa40... Shorter version: RSA-4096 is roughly 28bits over RSA-2048 (112 vs 140 bits).
makomk 11y ago
I don't trust the YubiKey Neo because of the security flaw that allowed anyone to trivially bypass PIN authentication and GPG sign stuff just by waving their RFID-enabled phone past your YubiKey, and because they insisted it didn't really matter because an attacker might have been able to learn your PIN anyway[1]. This is a general downside of smart card based devices; they're generally designed so that the only thing enforcing the use of the PIN/password is an if statement somewhere in the code, and if that contains a logic flaw or can be bypassed... [1] https://developers.yubico.com/ykneo-openpgp/SecurityAdvisory%202015-04-14.html https://developers.yubico.com/ykneo-openpgp/SecurityAdvisory...
- deleted 11y ago
  [deleted]
- nickik 11y ago
  Nobody will ever make a 100% secure system. What are the alternative NFC Smartcards that I can use? Yubico did not behave badly. Their products continue to improve in secuirty. What is your alternative setup that provides anything close the same usablity?
- Tharkun 11y ago
  That's not true. The whole point of a smart card is that it's NOT just an "if statement".
  - makomk 11y ago
    I'm afraid it is in many cases. The whole point of a smart card is to wrap enough hardware anti-tamper measures around that if statement in order to stop you from bypassing it.
dublinclontarf 11y ago
Nitrokey provides an open hardware implementation of OpenPGP Card, keeping your private keys off machine.

dimastopel 11y ago

What happens if you lose the card / key, or in case it becomes non-functional? How do you back-up the private key?

nickik 11y ago
Maybe read this post of mine: https://news.ycombinator.com/item?id=11437413 https://news.ycombinator.com/item?id=11437413
- dimastopel 11y ago
  Indeed, didn't think about having another stick for the backup.

nickik 11y ago

Yes. I use a Yubikey 4 Nano and I have it always plugged in to may Laptop. The Master key however is not on the Yubikey. It is only available on external encrpyted USB drive that I only use for certification. Currently their is no way to use your 4096bit key over NFC. The Yubikey NEO only supports 2048bit keys and the Yubikey 4 does not support NFC. So you have to either use a secondary key or expose yourself and put your private key on your phone. I fully expect Yubico to realease a Yubikey 4 with NFC sometime this year, and this would enable my optimal solution: I have a Smartphone and a Laptop. To securly use them, I should have 3 Yubikeys, 1 of them a Nano plus 2 USB Sticks. The Nano is always plugged into my laptop, exept for exeptional situations. One of the large Yubikeys is on my keyring, the other is at home as a backup. One USB stick is only for the Master Key and I would bring it along if I expected to use certification. The other USB Stick is a poor backup and savly stored at home, it also contains the Revocation Key. All this is pretty expensive and not really all that easy to set up but if you do it you have the great benefits, like ähh well äähh I guess other crypto nerds might think its cool.

Freak_NL 11y ago
Nice set up. It's all about proportionality. If your GPG-key (and SSH-key) grants you access to servers containing sensitive data placed there in good faith (think medical records), then having your private keys stored somewhere they can't be copied from without physically obtaining (and destroying) the keys is totally justified. And if you are doing it because, well, you can, then you are helping in making this knowledge available to the wider community.
- nickik 11y ago
  I have not jet transitioned to using SSH-keys from the Yubikey. I have some issues with the ssh-agent understanding that I use a PIV interface. I think pushing the bounds and evaluating usablity, maybe finding bugs is important. I still mostly do it for fun. I really like thinking threw different thread models and security systems. For example, compare the security gained by keybases new system (NaCL, device keys, tracking) with my old gpg/smartcard/wot system.
hollander 11y ago
Yubico themselve say that the 4096 bit key only adds 16% more security. So the Neo is practically as safe as the 4. https://www.yubico.com/2015/02/big-debate-2048-4096-yubicos-stand/ https://www.yubico.com/2015/02/big-debate-2048-4096-yubicos-... > While it is true that a longer key provides better security, we have shown that by doubling the length of the key from 2048 to 4096, the increase in bits of security is only 18, a mere 16%. Moreover, besides requiring more storage, longer keys also translate into increased CPU usage and higher power consumption.
- schlowmo 11y ago
  The math behind the security gain by increasing the key length of an RSA key seems slighly more complicated then one might expect. Here is a (short) introduction by the GnuPG folks: https://www.gnupg.org/faq/gnupg-faq.html#no_default_of_rsa4096 https://www.gnupg.org/faq/gnupg-faq.html#no_default_of_rsa40... Shorter version: RSA-4096 is roughly 28bits over RSA-2048 (112 vs 140 bits).

makomk 11y ago

I don't trust the YubiKey Neo because of the security flaw that allowed anyone to trivially bypass PIN authentication and GPG sign stuff just by waving their RFID-enabled phone past your YubiKey, and because they insisted it didn't really matter because an attacker might have been able to learn your PIN anyway[1]. This is a general downside of smart card based devices; they're generally designed so that the only thing enforcing the use of the PIN/password is an if statement somewhere in the code, and if that contains a logic flaw or can be bypassed... [1] https://developers.yubico.com/ykneo-openpgp/SecurityAdvisory%202015-04-14.html https://developers.yubico.com/ykneo-openpgp/SecurityAdvisory...

deleted 11y ago
[deleted]
nickik 11y ago
Nobody will ever make a 100% secure system. What are the alternative NFC Smartcards that I can use? Yubico did not behave badly. Their products continue to improve in secuirty. What is your alternative setup that provides anything close the same usablity?
Tharkun 11y ago
That's not true. The whole point of a smart card is that it's NOT just an "if statement".
- makomk 11y ago
  I'm afraid it is in many cases. The whole point of a smart card is to wrap enough hardware anti-tamper measures around that if statement in order to stop you from bypassing it.

dublinclontarf 11y ago

Nitrokey provides an open hardware implementation of OpenPGP Card, keeping your private keys off machine.