5 ms·

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-2

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.

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.