- cypherpunks-legacy - lists.cpunks.org

Re: More of Ben's blinding
by Anonymous 07 Jun '02

07 Jun '02

Jason Holt writes: > Anybody know of other patents which might get in the way? I'm worried > about Chaum's blind signature and undeniable signature patents, and want to > present as patent-free a system as possible. There was extensive discussion on coderpunks about possible patent implications of Wagner blinding. Using the g^b blinding makes things potentially a little worse, because it requires the server to publish g and g^k. This can be considered a public key, and brings the situation closer to the blind signature patent. Wagner blinding can be thought of as a blinded undeniable signature. It is like a blind signature in that the server doesn't see what it is "signing". And it is like an undeniable signature in that the validity can only be checked with the aid of the server. It seems likely that Wagner could have patented his blinding along these lines if he had wanted to. So the problem is, if this is a blind + undeniable signature, doesn't that suggest that it infringes on both the blind and the undeniable signature patents? To answer this you have to look at the claims in detail. You can differentiate from the undeniable signature patent in that there is no repudiation protocol in the ecash system - no way for the server to prove that a purportedly signed value is actually bad. (Of course this lack is a weakness in an ecash system, since the bank might like to be able to prove that bogus cash is just that; but if it were remedied then Wagner blinding would almost certainly infringe the undeniable signature patent.) Differentiation from the blind signature patent is done simply by asserting that this is not a signature. That's why we are always careful to put "sign" into quotes when referring to server operations. It's not a signature because there is no way to independently verify it, which one can argue is a de facto requirement for something to be considered a signature. But of course, by this definition the undeniable signature is not a signature either. Yet we call it a kind of signature. If the undeniable signature is a signature, then so is the Wagner blinding, and so it is covered by the blind signature patent. As you can see, the situation is murky. One salvation is that the blind signature patent will expire in about 3 years, and it is unlikely that you will be successful enough in any project that it would be worthwhile to sue you within that time frame. Besides, everyone who takes control of the blind sig patent soon goes broke, so they probably can't afford a lawyer to sue you anyway. You should be aware too that there are a number of credential patents, which you can find by searching on the word credential. > One more thing. If the issuer returns the signature: > > (h1*g^b1 *h2*g^b2 *h3*g^b3...)^k > > Can I separate out any of the h^k values? My system relies on that > being hard. Seems safe by the DDH assumption, which is that it is hard to recognize that (g, g^a, g^b, g^ab) have the DH relationship. If we let m = g^b then this is (g, g^a, m, m^a). In other words, we can't tell whether two different values g and m are both being raised to the same power. In your case, you know h1, h2, (h1h2)^k. If you could then find h1^k, you could construct a DDH tuple (h1, h1^k, h1h2, (h1h2)^k), so you could violate the DDH assumption. This is a little hand-wavy and only deals with the two element case, but an argument along these lines will probably work. > If I replace h1 with (g^b0) and get the issuer to sign: > > ((g^b0)*g^b1 *h2*g^b2 *h3*g^b3...)^k > > I should be able to divide the two results and get h1^k. But part of > the cut-and-choose protocol will be to require that the n/2 checked documents > are all valid and different from any previous instances of the protocol. So > it should be extremely hard for the user to sneak lots of previously used > values and fake h's (which are really blinding factors) into the unrevealed > documents. But are there other ways to separate out signatures on individual > h's? You're really going to remember all the discarded h values from all the previous instances of credential issuing? Seems like it might be a lot of data. How many h values do you typically expect? Maybe you could say more about the details of your credential system. Such a system built on Wagner blinding might be very interesting.

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number of bits in bent funtion
by Sandy Harris 07 Jun '02

07 Jun '02

Is there a general rule for the number of set bits in a bent boolean function of n input bits? I know from the Mister and Adams paper at SAC 96: http://adonis.ee.queensu.ca:8000/sac/sac96/papers.html that any 8-bit bent function has either 120 or 136 bits set. That's (2^8)/2 +- 8. Does that generalise to (2^n)/2 +- n for any even n? Or is there some other general rule?

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Gold Cards, No Credit Checks..
by Jocelyn Sastra 07 Jun '02

07 Jun '02

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RE: Degrees of Freedom vs. Hollywood Control Freaks
by Trei, Peter 07 Jun '02

07 Jun '02

> ---------- > From: Mike Rosing[SMTP:eresrch@eskimo.com] > Sent: Thursday, June 06, 2002 5:35 PM > To: cypherpunks(a)lne.com > Subject: Re: Degrees of Freedom vs. Hollywood Control Freaks > > On Thu, 6 Jun 2002, Tim May wrote: > > > (Booty being a black slang term for ass; no doubt related to "trunk" as > > body part, as in "swim trunks.") > > I always thought it came from pimp slang - booty being what you > take as a pirate. My kids love to shake their booty, and have no idea > of the history either :-) > > Patience, persistence, truth, > Dr. mike > There are doubtless etymologists who could answer this definitively. I don't have aceess to the OED online, which could at least give us info on how far back it goes. The question on hand is the origin of boot (British) vs trunk (American) for the storage at the rear of a sedan car. I really, really don't think either Tim or Mike are on the right track. American pimp slang is very unlikely to have affected British motoring jargon. Instead, I suggest the both 'boot' and 'booty' may come from a much older English usage of 'butt' to refer the the rear end of something - whether a person (buttocks), or the end of a spear or a cigarette (butt). Many horse-drawn coaches (and some early automobiles) had a luggage style trunk strapped on the back for storage. Thiis seems a source for the American 'trunk', and also give an alternative route to 'boot'. Many early automobile terms are from the French (chauffeur, carburetor ), and the French term for 'box' is 'boite', which could easily migrate in British English to 'boot'. Peter Trei

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Militants Are All-American Osamas
by John Young 07 Jun '02

07 Jun '02

http://www.nytimes.com/2002/06/07/opinion/07KRIS.html The New York Times, June 7, 2002 All-American Osamas Nicholas Kristof [Excerpt] Militia members and Al Qaeda members are remarkably similar. Both are galvanized by religious extremism (America's militias overlap with the Christian Identity movement, which preaches that Jews are the children of Satan and that people of color are sub-human), both see the United States government as utterly evil, and both are empowered by the information revolution that enables them to create networks, recruit disciples and trade recipes for bio- and chemical weapons. It would be a mistake to put one's faith in the militias' eternal incompetence. Jessica Stern of Harvard has written about an anti-government activist named James Dalton Bell, who earned a degree in chemistry from M.I.T. and is unquestionably brilliant. By age 14, he says, "I was studying the isomerization of benzyl thiocyanate to the isocyanate." Weren't we all? But Mr. Bell, who is now in jail, is also believed by the authorities to have manufactured sarin, a nerve gas, in his basement. He led a chemical attack against an I.R.S. office and wrote an Internet book called "Assassination Politics," which outlines a very clever scheme to pay for contract killings of federal officials with digital cash in a way that preserves anonymity at both ends. There is also evidence that Mr. Bell talked "hypothetically" of poisoning a city's water supply. -----

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by Alan Canas 07 Jun '02

07 Jun '02

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2000 Year old bread recipe actually helps you lose weight!
by Mary Life 07 Jun '02

07 Jun '02

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07 Jun '02

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by Abigail 07 Jun '02

07 Jun '02

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Re: Affordable Advertising
by Elite Creative Studios 07 Jun '02

07 Jun '02

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