7 ms·

Seriously, the default options to ssh-keygen should be all anybody needs. If you need to pass arguments to increase the security of the generated key, then the

Seriously, the default options to ssh-keygen should be all anybody needs. If you need to pass arguments to increase the security of the generated key, then the software has completely failed its purpose. Passing arguments should only be for falling back on less secure options, if there is some limiting factor for a particular deployment. There is absolutely no reason to pass arguments to ssh-keygen. If it is actually deemed necessary to do so, then that package's installation is inexcusably broken.

sillysaurus3 10y ago
By default, ssh-keygen leaks info about your computer (``user@host''). Passing -C "" takes care of this. I just throw a script in my ~/bin folder called `keygen`: exec ssh-keygen -t rsa -b 4096 -C "" "$@"
- hk__2 10y ago
  Why not just use an alias? alias keygen="ssh-keygen -t rsa -b 4096 -C ''"
  - liw 10y ago
    Aliases are per shell process. You need to reload your .bashrc (or whatever file you define aliases in) in every shell. Shell scripts are instantly available in all shell instances. Also, shell scripts can be invoked by shell scripts, which aliases can't.
    - hk__2 10y ago
      I agree, but for something as simple as that I’d prefer a script to use `ssh-keygen` instead of relying on the presence of a one-line script in the PATH.
- Godel_unicode 10y ago
  If you're concerned about hostname leakage in your pubkeys, you're almost certainly doing something wrong.
  - sillysaurus3 10y ago
    If you want SSH access to Github or Gitlab, you'll need to paste your pubkey there. Leaking your user@host can be a concern if you're trying to maintain anonymity, e.g. Gwern, particularly if your username is your real name. You can strip out the user@host part from the paste, but it's safer to just get rid of it. It's easy to accidentally paste the whole thing into an .ssh/authorized_keys file, for example. Admittedly this isn't an issue for most people.
    - glandium 10y ago
      If you're trying to maintain anonymity, why is your username your real name?
      - sillysaurus3 10y ago
        Even if it's not, your default hostname when using a MacBook Pro is typically "<username>s-MacBook-Pro.local" which reveals you're using a MacBook Pro. That info leak probably doesn't matter, but generally you want to reveal as little information as possible.
        nitrogen 10y ago
        As one example, a hostname leak might hypothetically be useful for a spearfishing+XSS attack.
        acranox 10y ago
        What kind of person cares enough about anonymity to change the comment in their ssh key, but not change the default hostname of their Mac? That person is very inconsistent.
        minitech 10y ago
        Why does ssh-keygen include unnecessary information by default?
Spydar007 10y ago
> Passing arguments should only be for falling back on less secure options This is the case with the secure-delete package for srm and sfill. Each argument changes the writes to make them less secure.
mSparks 10y ago
Well. OP says ->Generate your new sexy Ed25519 key I too, say, No f'ing thanks https://en.wikipedia.org/wiki/Curve25519 https://en.wikipedia.org/wiki/Curve25519 In cryptography, Curve25519 is an elliptic curve offering 128 bits of security - The curve is birationally equivalent to Ed25519, a Twisted Edwards curve. Ecrypt II - the EU project into encryption security says: https://www.keylength.com/en/3/ https://www.keylength.com/en/3/ That gives you Very short-term protection against small organizations Should not be used for confidentiality in new systems and is equivelent to an 816bit RSA key So how is this new key "Sexy" in any way.
- hannob 10y ago
  First of all the Ecrypt project is is really outdated. Second you're reading the table wrong. Curve25519 gives you 128 bit of symmetric security, but the curve is 255 bit long. So from your table this compares to 3248 RSA. Third I'm no fan of such key number tables, it's a bit arbitrary and doesn't really reflect the complexities of modern cryptography.
  - mSparks 10y ago
    so we should just take yours, and a random blogs word for it over a group of eu cryptologists paid by the eu to keep our data safe from the us and russian state hackers. again. no thanks. you want to join all the american idiots listening to such nonesense disinformation and give all your data to the ruskies. be my guest.
    - acqq 10y ago
      The paper of the designers of ed25519 specifies the design of the curve: the modulo is 2 to the 255th power - 19 (note that it's how the curve got its name), in the table you quote it's equvalent to (roughly) 3000 RSA bits: https://ed25519.cr.yp.to/ed25519-20110926.pdf https://ed25519.cr.yp.to/ed25519-20110926.pdf
    - sctb 10y ago
      Please comment civilly and substantively or not at all. https://news.ycombinator.com/newsguidelines.html https://news.ycombinator.com/newsguidelines.html
makomk 10y ago
Not all systems that you might want to use your keys on support Ed25519, and this was especially true when it was first introduced to OpenSSH. Similarly not everything can handle the new key format. (Interestingly, there's another way to increase the resistance of SSH private keys to password brute-forcing that uses PBKDF2 and is more widely supported, but there's no way to create keys that use it using OpenSSH itself.)
- andai 10y ago
  Are you referring to something like this? http://blog.patshead.com/2013/09/generating-new-more-secure-ssh-keys.html http://blog.patshead.com/2013/09/generating-new-more-secure-...

sillysaurus3 10y ago

By default, ssh-keygen leaks info about your computer (``user@host''). Passing -C "" takes care of this. I just throw a script in my ~/bin folder called `keygen`: exec ssh-keygen -t rsa -b 4096 -C "" "$@"

hk__2 10y ago
Why not just use an alias? alias keygen="ssh-keygen -t rsa -b 4096 -C ''"
- liw 10y ago
  Aliases are per shell process. You need to reload your .bashrc (or whatever file you define aliases in) in every shell. Shell scripts are instantly available in all shell instances. Also, shell scripts can be invoked by shell scripts, which aliases can't.
  - hk__2 10y ago
    I agree, but for something as simple as that I’d prefer a script to use `ssh-keygen` instead of relying on the presence of a one-line script in the PATH.
Godel_unicode 10y ago
If you're concerned about hostname leakage in your pubkeys, you're almost certainly doing something wrong.
- sillysaurus3 10y ago
  If you want SSH access to Github or Gitlab, you'll need to paste your pubkey there. Leaking your user@host can be a concern if you're trying to maintain anonymity, e.g. Gwern, particularly if your username is your real name. You can strip out the user@host part from the paste, but it's safer to just get rid of it. It's easy to accidentally paste the whole thing into an .ssh/authorized_keys file, for example. Admittedly this isn't an issue for most people.
  - glandium 10y ago
    If you're trying to maintain anonymity, why is your username your real name?
    - sillysaurus3 10y ago
      Even if it's not, your default hostname when using a MacBook Pro is typically "<username>s-MacBook-Pro.local" which reveals you're using a MacBook Pro. That info leak probably doesn't matter, but generally you want to reveal as little information as possible.
      - nitrogen 10y ago
        As one example, a hostname leak might hypothetically be useful for a spearfishing+XSS attack.
      - acranox 10y ago
        What kind of person cares enough about anonymity to change the comment in their ssh key, but not change the default hostname of their Mac? That person is very inconsistent.
        minitech 10y ago
        Why does ssh-keygen include unnecessary information by default?

Spydar007 10y ago

> Passing arguments should only be for falling back on less secure options This is the case with the secure-delete package for srm and sfill. Each argument changes the writes to make them less secure.

mSparks 10y ago

Well. OP says ->Generate your new sexy Ed25519 key I too, say, No f'ing thanks https://en.wikipedia.org/wiki/Curve25519 https://en.wikipedia.org/wiki/Curve25519 In cryptography, Curve25519 is an elliptic curve offering 128 bits of security - The curve is birationally equivalent to Ed25519, a Twisted Edwards curve. Ecrypt II - the EU project into encryption security says: https://www.keylength.com/en/3/ https://www.keylength.com/en/3/ That gives you Very short-term protection against small organizations Should not be used for confidentiality in new systems and is equivelent to an 816bit RSA key So how is this new key "Sexy" in any way.

hannob 10y ago
First of all the Ecrypt project is is really outdated. Second you're reading the table wrong. Curve25519 gives you 128 bit of symmetric security, but the curve is 255 bit long. So from your table this compares to 3248 RSA. Third I'm no fan of such key number tables, it's a bit arbitrary and doesn't really reflect the complexities of modern cryptography.
- mSparks 10y ago
  so we should just take yours, and a random blogs word for it over a group of eu cryptologists paid by the eu to keep our data safe from the us and russian state hackers. again. no thanks. you want to join all the american idiots listening to such nonesense disinformation and give all your data to the ruskies. be my guest.
  - acqq 10y ago
    The paper of the designers of ed25519 specifies the design of the curve: the modulo is 2 to the 255th power - 19 (note that it's how the curve got its name), in the table you quote it's equvalent to (roughly) 3000 RSA bits: https://ed25519.cr.yp.to/ed25519-20110926.pdf https://ed25519.cr.yp.to/ed25519-20110926.pdf
  - sctb 10y ago
    Please comment civilly and substantively or not at all. https://news.ycombinator.com/newsguidelines.html https://news.ycombinator.com/newsguidelines.html

makomk 10y ago

Not all systems that you might want to use your keys on support Ed25519, and this was especially true when it was first introduced to OpenSSH. Similarly not everything can handle the new key format. (Interestingly, there's another way to increase the resistance of SSH private keys to password brute-forcing that uses PBKDF2 and is more widely supported, but there's no way to create keys that use it using OpenSSH itself.)

andai 10y ago
Are you referring to something like this? http://blog.patshead.com/2013/09/generating-new-more-secure-ssh-keys.html http://blog.patshead.com/2013/09/generating-new-more-secure-...