Re:Generating 16384 Bit SSH Keys
by AdamGibbins on Thursday September 27, 2012 @07:31PM
(#4583474)
This is a valid point however unfortunately is limited to systems running recent versions of OpenSSH; ECSDA is relatively new. If you connect to a large amount of boxes (as do I), your ECDSA simply will not work on older pre-ECDSA versions of OpenSSH.
That said, nothing preventing you having a mixture of keys for different hosts and modifying your ssh_config to use the correct key dependant on the domain.
Re:Generating 16384 Bit SSH Keys
by ComputerGuru on Thursday September 27, 2012 @07:36PM
(#4583498)
Small ECDSA key by default, 16kbit RSA fallback?
Both are very secure, but ECDSA will not have the long negotation times. Problem solved?
You do not need a 16k RSA key.
Re:Generating 16384 Bit SSH Keys
by ComputerGuru on Thursday September 27, 2012 @11:39PM
(#4584197)
Or whatever. Just giving an example.
I have the following in my ssh config file.
Host *
IdentityFile ~/.ssh/id_ecdsa
IdentityFile ~/.ssh/id_rsa
HashKnownHosts yes
VisualHostKey yesLooks like it's from OpenSSH 5.7 released on Jan 25, 2011.
Re:Generating 16384 Bit SSH Keys
by AdamGibbins on Thursday September 27, 2012 @07:42PM
(#4583516)
Which is unfortunately a very new version compared to most distros. CentOS 6 for example has only 5.3. Debian Squeeze, 5.5. Ubuntu Precise, 5.9.
Use this: ssh-keygen -b 521 -t ecdsa
That's (a lot) faster than RSA 16384 bit keys. A 200bit ECDSA key is +- (there's many factors involved) equivalent to a 2048bit RSA key.
Also the 521bit ECDSA not only verifies faster, it generates instantly (on current hardware), instead of taking a few coffess with the 16K RSA.
Finally, remember that, by the time we've enough computer power to brute force either of the above, one of these will probably happen:
- RSA or ECDSA may be logically broken
- you will be dead
- the hardware and software will not run anymore
- a new computer power breakthrough will make the choice of strength and cipher irrelevant (one can hope)