RE: [GD-General] serial numbers

[Gareth L. <GL...@cl...>]

Just make the serial number out of two parts. The first part is a =
sequential
number, then hash the name and the serial number.

> -----Original Message-----
> From: Ignacio Casta=F1o [mailto:cas...@ya...]
> Sent: 27 May 2003 17:37
> To: gam...@li...
> Subject: Re: [GD-General] serial numbers=20
>=20
>=20
> J C Lawrence wrote:
> > Typical forms I've seen are a one-way hash ala MD5 of the=20
> public data,
> > along with a secret.  The resultant string (often with=20
> another secret)
> > is then digitally signed with the resultant string,=20
> sometimes with a CRC
> > or other padding data appended..  The application then verifies the
> > signature to check that the key is of valid form, and the=20
> central site
> > can check that the key is legit.
>=20
> Thanks, I was looking for something like that so, but I still have a
> problem. I create a message using the secret and the public data, and
> generate the key aplying MD5 to it, so when the user logs in,=20
> he provides
> the previous key and the public data. I know the secret, so I=20
> can recompute
> the key and validate the key that the user provided.
>=20
> MD5 is not trivially reversible, so this seems to work.=20
> However, if two
> users have the same name, the keys will also be the same, and=20
> some products
> don't requiere an username, so in that case I would have a single =
key!
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> How can I solve that? I'd like to add a random part to the=20
> encoded message,
> but then I don't know how to validate it...
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> Thanks in advance,
>=20
>=20
> Ignacio Casta=F1o
> cas...@ya...
>=20
>=20
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>=20
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>=20