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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 encrpy

by 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).
- andreareina 11y ago
  18 bits translates to a ~250k-fold increase in effective security. Am I missing something, or is this just bad math on Yubico's part?
  - hollander 11y ago
    It's probably marketing.
- nickik 11y ago
  Thats not the point. I already had a 4096 key and its already distributed and certified by people. I will not change all of my system back to 2048 just so I can use a SmartCard. If I had started with Yubikeys when I started with GPG I would have used 2048 and updated when the Smartcard technology improved. Additionally I have not a huge need for gpg messages on my Smartphone, so its not a big problem.
- throwaway7767 11y ago
  18 additional bits of security means a bruteforce attack is 2^18 (262144) times harder. Quite a long way away from "16% more security". Yubico is intentionally obfuscating their words here by talking about the percentage increase between number of bits of security so that people will walk away with this exact misunderstanding. There is argument to be made that 4096-bit RSA keys are unnecessary. But this isn't it.
potisje 11y ago
Why don't you use read-only media (CDs, DVDs) for your master key (backup)? Those are very hard to temper with, while USB sticks are trivial to temper with (be it accidentally or by someone with malicious intent).
- nickik 11y ago
  I dont have the hardware to do that but it would be a good idea.

by nickik 11y ago

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).
andreareina 11y ago
18 bits translates to a ~250k-fold increase in effective security. Am I missing something, or is this just bad math on Yubico's part?
- hollander 11y ago
  It's probably marketing.
nickik 11y ago
Thats not the point. I already had a 4096 key and its already distributed and certified by people. I will not change all of my system back to 2048 just so I can use a SmartCard. If I had started with Yubikeys when I started with GPG I would have used 2048 and updated when the Smartcard technology improved. Additionally I have not a huge need for gpg messages on my Smartphone, so its not a big problem.
throwaway7767 11y ago
18 additional bits of security means a bruteforce attack is 2^18 (262144) times harder. Quite a long way away from "16% more security". Yubico is intentionally obfuscating their words here by talking about the percentage increase between number of bits of security so that people will walk away with this exact misunderstanding. There is argument to be made that 4096-bit RSA keys are unnecessary. But this isn't it.

potisje 11y ago

Why don't you use read-only media (CDs, DVDs) for your master key (backup)? Those are very hard to temper with, while USB sticks are trivial to temper with (be it accidentally or by someone with malicious intent).

nickik 11y ago
I dont have the hardware to do that but it would be a good idea.