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Upgrade your SSH keys

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Re: Upgrade your SSH keys

#71

Post by mSparks »

developer2 wrote: post #60

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…

Well. OP says ->Generate your new sexy Ed25519 key

I too, say, No f'ing thanks 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/

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.

Re: Upgrade your SSH keys

#72

Post by dredmorbius »

technion wrote: post #13
based2 wrote: post #5

https://www.reddit.com/r/netsec/comments/543ncp/upgrade_your...

I always find it interesting to see the disparity between comments here, and in /r/netsec on matters like this. Here: Generally positive. Netsec: Most upvoted comments being complaints and assertions that it's bad advice. And for some reason, upvoted comments about NSA involvement in curves (which is exactly what 25519 is not).

Constructing an open-access forum such that the most highly rated comments actually have high levels of information and relevance is difficult at best. Probably impossible without some specific test / proof of competence in the area.

Re: Upgrade your SSH keys

#73

Post by Klathmon »

technion wrote: post #13
based2 wrote: post #5

https://www.reddit.com/r/netsec/comments/543ncp/upgrade_your...

I always find it interesting to see the disparity between comments here, and in /r/netsec on matters like this. Here: Generally positive. Netsec: Most upvoted comments being complaints and assertions that it's bad advice. And for some reason, upvoted comments about NSA involvement in curves (which is exactly what 25519 is not).

I've started moving away from reddit for any kind of actual discussion about technical topics. It's just so... Toxic.

I don't know if it's just my point of view changing, or if it's gotten worse over the last few years, but when I see a thread there later, the top comments are always negative, dismissive, and so full of bullshit.

Just look at the recent Lenovo issue, HN had some good discussion on on what could be the actual causes and how to fix some of these problems (and why MS isn't entirely off the hook there), but reddit was just full of "Microsoft loves Linux!" Jokes and whichunting with very little to go on.

Re: Upgrade your SSH keys

#74

Post by hannob »

mSparks wrote: post #71
developer2 wrote: post #60

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…

Well. OP says ->Generate your new sexy Ed25519 key I too, say, No f'ing thanks 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/ That gives you Very short-term protection against small…

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.

Re: Upgrade your SSH keys

#75

Post by hannob »

LeoPanthera wrote: post #9

Can someone explain to me why RSA 2048 is "recommended to change"? It's still the default for gpg keys and as far as I know is widely thought to be secure for at least few hundred years!

2048 bit is fine.

It's probably not secure for a hundred years because of quantum computers. But none of the currently supported algs in openssh protects against quantum computers, therefore there's nothing you can do against it right now.

Re: Upgrade your SSH keys

#76

Post by rockdoe »

mSparks wrote: post #71
developer2 wrote: post #60

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…

Well. OP says ->Generate your new sexy Ed25519 key I too, say, No f'ing thanks 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/ That gives you Very short-term protection against small…

You are misunderstanding. Curve25519 offers 128 bits of symmetric security, or the equivalent of a 256 bit elliptic curve key.

Re: Upgrade your SSH keys

#77

Post by hannob »

tptacek wrote: post #7
MichaelRenor wrote: post #3

I disagree with the author. Before you go upgrading into ed25519, beware that the NSA/NIST is moving away from elliptical curve cryptography because it's very vulnerable to cracking with quantum attacks[0]. "So let me spell this out: despite the fact that quantum computers seem to be a long ways off and reasonable quantum-resistant replacement algorithms are nowhere to be seen, NSA decided to make this announcement p…

Both RSA and Elliptic Curve will fall to practical quantum computing, so the idea that you should use (weaker, slower) RSA today instead of curves because of QC is... dubious. If you see quantum computing as a practical threat (because: you're encrypting and storing static data that needs to resist cryptanalysis for 20-50 years), you need to use a post-quantum cryptosystem. Unfortunately: nobody knows which pq system…

There is one argument to be made in favor of large key RSA when it comes to quantum computers: ECC may fall a bit earlier. There can be a situation where it's feasible to produce a quantum computer large enough to tackle a 255 bit ECC key, but not a 4096 RSA key. I have heard from (a few) cryptographers that this is a reason to stick with "old school" DH/RSA crypto.

I discussed this with various people involved in the postquantum debate and the general feedback I got was that this is likely not a big issue, because once quantum computers can be scaled it'll probably not be that hard to scale them up to RSA-breaking size. I think DJB once said something like "this will buy you a year" to me.

Re: Upgrade your SSH keys

#78

Post by hk__2 »

sillysaurus3 wrote: post #65
developer2 wrote: post #60

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…

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 "" "$@"

Why not just use an alias?

    alias keygen="ssh-keygen -t rsa -b 4096 -C ''"

Re: Upgrade your SSH keys

#79

Post by mSparks »

hannob wrote: post #74
mSparks wrote: post #71

Earlier quoted context omitted.

Well. OP says ->Generate your new sexy Ed25519 key I too, say, No f'ing thanks 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/ That gives you Very short-term protection against small…

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.

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.

Re: Upgrade your SSH keys

#80

Post by mSparks »

rockdoe wrote: post #76
mSparks wrote: post #71

Earlier quoted context omitted.

Well. OP says ->Generate your new sexy Ed25519 key I too, say, No f'ing thanks 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/ That gives you Very short-term protection against small…

You are misunderstanding. Curve25519 offers 128 bits of symmetric security, or the equivalent of a 256 bit elliptic curve key.

even if that is true. its still not enough to protect anything of value.
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