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Date: Fri, 25 Jan 2013 00:48:41 +0100
From: Frank Dittrich <>
Subject: Re: Formats ssh and ssh-ng

On 01/24/2013 08:06 PM, magnum wrote:
> Can't you batch creation of a million test files and try cracking them? That's what I did with RAR. It's a pity key file creation is so slow :-)

On my laptop (Intel(R) Core(TM) i3-2367M CPU @ 1.40GHz):

$ time ( for i in `seq 1 100`; do ssh-keygen -t rsa -f
/home/fd/.ssh/id_rsa_000-test$i -P test$i -N test$i > /dev/null ; done )

real	0m31.321s
user	0m30.490s
sys	0m0.532s
$ time ( for i in `seq 101 1100`; do ssh-keygen -t rsa -f
/home/fd/.ssh/id_rsa_000-test$i -P test$i -N test$i > /dev/null ; done )

real	4m51.946s
user	4m44.037s
sys	0m5.550s

(BTW: ssh-keygen requires a minimum password length of 5. But I don't
know if this is true for all versions.)

That means about 0.3 seconds per key, or almost 3.5 days for 1 million keys.
CPU doesn't seem to be the bottleneck.
More probably, the system is running out of entropy.

john cracked all 1100 passwords immediately in single mode after
converting them using
$ ./ /home/fd/.ssh/id_rsa_000-test*[0-9] > sshng-test


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