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Date: Sat, 18 Jul 2015 22:22:55 +0300
From: Solar Designer <>
Cc: Jeremy Spilman <>
Subject: Re: [PHC] patents

On Thu, Jul 16, 2015 at 02:17:30PM -0700, Bill Cox wrote:
> I think Jeremy might be able to rework his patent into a "business-model"
> patent.  I am not personally aware of anyone offering to do the password
> hashing with a central ROM under the control of another company that
> provides this as a service.  This is what I think his company does.
> Assuming he wants to carve out this space narrowly, he might be able to
> convince the patent office to allow his patent with the additional steps of
> transmitting the salted password hash over the Internet from a client
> company to the company providing the ROM hashing service, after the first
> hashing the password with a secret salt which is never transmitted.  I
> think Jeremy's main idea which _might_ be new is securing the password hash
> with secret salt before transmitting it to an untrusted ROM-based hashing
> service.  It's not a bad idea, but it is not what he patented.

I wouldn't be happy with seeing this patented either, in part since I
was also thinking in the same direction back in 2012, and I am still
considering starting a business like this myself.  Now that I have
learned of Jeremy's patent and the older one, I felt I'd have to focus
solely on the delegation and port-hardness aspects, with non-secret ROM.
As an extra and a partial mitigation of making the ROM non-secret, I
think using a secret key that is not part of the large ROM would still
be OK.

> His patent
> covers any sane use of ROM in password hashing, and therefore is invalid
> due to prior art.

It is not my understanding that any sane use of ROM in password hashing
is covered by the patent(s).  I think port-hardness with a non-secret
ROM is not covered.  But I am not a patent lawyer.


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