Hi Zooko,

>  One of my earlier notes on this subject to this
> list, [2], says that I experimented with...
> ...
> So, I ask everyone, what is the simplest efficient way
> to take a secret 96-bit input, and produce an output
> between [1, n) ...
sci.crypt is probably better equipped to answer the question. There
are quite a few PhDs and consultants who are active in the group.

Jeff

On 3/3/09, zooko <[email protected]> wrote:
>
> On Feb 24, 2009, at 10:39 AM, Wei Dai wrote:
>
> > CTR_Mode<AES> should also work, but there's a bug (which will be
> > fixed soon) that makes the RandomNumberGenerator interface
> > inaccessible.
>
> So a CTR_Mode<AES> instance can be passed as an argument of type RNG
> starting with Crypto++ v5.6?
>
> I am about to implement "deterministic generation of private key from
> small seed" [1] for Tahoe, so I need to come up with a function that
> takes an input of 96 bits and produces a 192-bit ECDSA private key.
> I'm going to have to support this functon forever (approximately) for
> backwards-compatibility reasons.  I would really like the next
> release of Tahoe to be compatible with older Crypto++ versions.  Also
> I would really like for this function to be as simple and clear as
> possible so that I can easily explain to other people how to
> implement it compatibly.
>
> My current code to do this is below (and I've earlier posted it to
> this list: [2]), but I'm not entirely satisfied with it because it
> seems rather ad-hoc.  One of my earlier notes on this subject to this
> list, [2], says that I experimented with using X917RNG with a
> customization of Salsa20 to pretend that it has a block size of 32.
>
> So, I ask everyone, what is the simplest efficient way to take a
> secret 96-bit input, and produce an output between [1, n) such that
>
> a) if you know the 96-bit secret and use this algorithm, you always
> get the same output, and
> b) if you don't know the 96-bit secret, you can't learn anything
> about the output
>
> Unless I, or someone, can think of a problem with this way to do it,
> or can propose a better way to do it, then I guess I'm going to
> proceed with this and then I'll be committed to maintaining it for a
> while.
>
> Regards,
>
> Zooko
>
> [1] http://allmydata.org/trac/pycryptopp/ticket/2 # deterministic
> generation of private key from small seed
> [2] http://groups.google.com/group/cryptopp-users/browse_thread/
> thread/f30427601a5884f6
> [3] http://groups.google.com/group/cryptopp-users/msg/c1041e508c8d8705
>
> [SNIP]

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