3DES key-length

[Hari-Isoft]

Interesting story, indeed!

> > I am interested in the export regulations concerning openssh in USA. Any
> > idea on this ?
>
> Should be pretty free of US regs; all the crypto modules are imported
> from Canada / Germany / Etc.

But, how about the regulations concerning export of OpenSSH from the USA to
other countries, (because of 128 bit key encryption used!) ?

Thanks,
Hari

----- Original Message -----
From: "Dan Kaminsky" <dan at doxpara.com>
To: "Hari-Isoft" <hari at isofttechindia.com>
Cc: <openssh-unix-dev at mindrot.org>
Sent: Tuesday, December 03, 2002 7:21 PM
Subject: Re: 3DES key-length


> > I would like to know the key-length used for 3DES data encryption in
> > openssh.
> > I thought that it should be 192 (3 * 64) bits, but the sshd man page
states
> > 128 bit key used for 3DES.
>
> This is one time when Marketing got it right.
>
> Key length is a bit messy...3DES uses three 64 bit keys, but 8 bits of
> each key is parity(i.e. doesn't contribute to security value).  So
> there's 56*3 or 168 bits of entropy behind each 3DES key.
>
> If I remember correctly, there's an optimized model of 3DES cracking
> that reduces the complexity of 168 bit 3DES to 112 bits.  (2DES is only
> 1 bit more complex to break than straight DES, due to this attack.)  But
> 3DES has undergone vastly more cryptanalysis than any other algorithm,
> so it's a bit unfair to say it's inferior to those ciphers that directly
> use 128 bit keys (Blowfish, AES, etc.)
>
> So -- instead of mucking with the details of 64 bit keys that are really
> 56 bit but are used thrice to give 192 bits of keying material with only
> 168 bits used but with only 112 bits of security on a very widely
> trusted algorithm...
>
> It's 128 bit.
>
> > Also, I would like to know the 3des key negotiation - who generates the
key
> > (the client or the server).
>
> Don't remember off the top of my head, I'll dive through the specs if
> nobody else pipes up.  Under DH, neither side actually needs to generate
> the key -- it can be the unified outcome of their asymmetric exchange.
> > I am interested in the export regulations concerning openssh in USA. Any
> > idea on this ?
>
> Should be pretty free of US regs; all the crypto modules are imported
> from Canada / Germany / Etc.
>
> Yours Truly,
>
> Dan Kaminsky
> DoxPara Research
> http://www.doxpara.com
>