December 2003 - cypherpunks-legacy

summary of talk by Birgit Pfitzmann on "Asymmetric and Anonymous Fingerprinting"
by nelson＠media.mit.edu 17 Dec '03

17 Dec '03

I just heard an interesting talk by Birgit Pfitzmann of the University of Hildesheim on "asymmetric and anonymous fingerprinting". I thought I'd write up a little summary of the techniques she presented, what they are good for. More detail (including papers) is available on the web at http://www.semper.org/sirene/ see below for specific references Quick summary: background for what fingerprints are and what they're good for traditional fingerprints are symmetric - buyer and merchant both have the fingerprinted data scheme for asymmetric fingerprinting so only buyer has the fingerprint but merchant can still trace fingerprint scheme for anonymous asymmetric fingerprinting so buyer remains anonymous Fingerprinting is something like watermarking. The basic idea is giving merchants of data some way to protect themselves if unauthorized copies of the data are made. Watermarking is useful for proving that a document came from some provider. Fingerprinting goes further in that the merchant gives different buyers subtly different copies of the data - if a copy shows up, the merchant can look at the fingerprint imbedded in the data and figure out who leaked the copy. Traditional fingerprinting has a few hard problems. First, the fingerprint marks need to be embedded in the data without causing any significant change to the data itself. But this goal is in tension with the goal of having the fingerprint survive through potentially lossy transforms. Ie, if I want to fingerprint an audio stream I could modify some of the least significant bits. But then if that audio stream were compressed through some lossy filter the fingerprint might be removed. Furthermore, you want to make it difficult for multiple buyers to collude to remove your fingerprint. Ie: if two buyers compare their purchased data they can identify the parts that are different and conclude that these parts are part of the fingerprint. A good fingerprint coding will make this sort of collusion difficult, although there's a tradeoff between the size of the fingerprint and the number of colluders you can protect against. In a typical fingerprint protocol the merchant calculates the fingerprint, applies it to the data, and then gives the marked copy to the buyer. This is OK except that it means that if an illicit copy of the data shows up no one can prove whether it was the buyer who was responsible for the copy or if it was the merchant. At first glance this might seem silly (what incentive does the merchant have to make illegal copies?) but you can imagine several scenarios where this is a problem. For instance, the buyer wants to be sure it's impossible for the merchant to frame him or her. Also if the merchant's data storage is insecure then someone could steal the merchant's copy and the buyer would be falsely accused. So traditional fingerprints are something like symmetric authentication schemes: both the merchant and the buyer have the secret. The asymmetric fingerprint scheme presented provides a way for the merchant to guarantee that the buyer gets a fingerprinted copy of the data but *the merchant never has a copy of the data with the fingerprint*. Ie: the fingerprinted version is a secret that only the buyer has. This is analagous to asymmetric authentication: people can check that the fingerprint belongs to a buyer but they can't generate it. If a copy with the fingerprint is released then the world knows which buyer is to blame. The details of how this is accomplished were presented but I confess I didn't follow them very closely. Each buyer has a public/secret key pair: the fingerprint is keyed to the buyer's secret key. With a bit commitment algorithm it's possible to arrange it so that the merchant can generate a fingerprint based on the buyer's secret key without actually seeing the key or the fingerprint itself. The merchant can check if a copy of his data came from a buyer by checking the fingerprint with the buyer's public key. I'm sure the paper has the details of the actual algorithm. The system sketched above is not anonymous - the merchant knows the identity of the buyer. The next goal is to make it possible for a buyer to get a fingerprinted copy of data from the merchant without revealing his or her identity. Full anonymity is currently not possible. I didn't follow this very well, but my understanding is there's some scheme where the buyer registers a pseudonym with a third party who then works with the merchant to perform the transaction. The third party doesn't need to be trusted. Consult the web site for details. Overall, this work seems like a nice improvement on fingerprinting schemes. The asymmetry seems like a big win to me. The two directly relevant papers are linked from http://www.semper.org/sirene/lit/abstr96.html Birgit Pfitzmann, Matthias Schunter: Asymmetric Fingerprinting; Eurocrypt 96, LNCS 1070, Springer-Verlag, Berlin 1996, 84-95. Birgit Pfitzmann, Michael Waidner: Anonymous Fingerprinting; IBM Research Report RZ 2881 (#90829) 11/18/96, IBM Research Division, Zürich, Nov. 1996.

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Re: Decline of Science ?? (Was: Stinger Specs)
by E. Allen Smith 17 Dec '03

17 Dec '03

From: IN%"asgaard(a)Cor.sos.sll.se" "Asgaard" 6-DEC-1996 09:42:25.11 >and a PCR biochemist hacking DNA doesn't know shit about immunology >or molecular neurology. In bio-science there is a discipline >which tries to put all such kinds of specialties into a broader >understanding of the human/animal body and soul - it's called >physiology, and is a declining field with chronic lack of funds; >not much money in it. I'm sure there is a comparable discipline While not a bio_chemist_, I am a molecular geneticist who has heavily used PCR in the past - and am interested in learning more about why particular "tweaks" work the way they do. I'm also probably more familiar with immunology and with molecular neurology (at least if you're meaning neuropsychopharmacology) than most scientists outside those fields - certainly more so than most people. There are still a few of us like that... and I'm Generation 3 in TCMay's terminology. BTW, I have taken physiology, and in its human physiology manifestation it's actually a growing field in the biomedical sciences area. Sure, a lot of people are overspecializing up the wazoo... but those of us who don't are getting more done. -Allen

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Please post Eudora PGP plugin URL
by ! Drive 17 Dec '03

17 Dec '03

Or Email it to me Thanks in advance

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"Family Channel" of the Internet?
by Ken Kirksey 17 Dec '03

17 Dec '03

I had a rather interesting conversation today with a man who works for an individual who is getting into the ISP business. The guy freely admitted that he was not a technical kind of guy, and was only repeating what he had been told. The gist of the conversation: this company was going to try to position itself as, and I quote, "The Family Channel of the Internet" by going SurfWatch one better. If you sign up with them as your ISP, you'll only be able to access sites that they have personally inspected and approved. He said that they were going to do this, again I quote, "using the same encryption that Visa and Mastercard use." The last statment pegged my bogometer, of course. Now, since I know that I don't know everything about crypto, and I know even less about the inner workings of IP, I'm going to pose a couple of questions: 1) Is it technically possible for them to limit access to only approved IP addresses? If so, how can they do this, and is it possible to get around these measures. 2) What in the world would SET--I assume that was what he was talking about--have to do with this? 3) In general, how would you use crypto to ensure that your users only connected to approved sites, regardless of the platform or browser software they were using? I asked the guy to send me some technical details. If I receive them, I'll share unless he makes me sign an NDA. Ken

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Re: Decline of Science ?? (Was: Stinger Specs)
by Adamsc＠io-online.com 17 Dec '03

17 Dec '03

On Fri, 6 Dec 1996 13:10:57 +0100 (MET), Asgaard wrote: >> to participate. junior colleges are graduating students who >> would not have passed out of tenth grade 20-30 years ago. > ><etc. about Gen 3 (-5) as in Tim's example> > >Isn't this merely an effect of mass education instead of >elite_only education? And the peak performers will do as Not really; high schools have gotten worse -- it was amusing for me to read Robert Heinlein's rant in the first chapters of "Have spacesuit..." because the school he was complaining about would have been GOOD today. >A real difference, though, is the relative lack of multidisciplinary >theorists nowadays, I mean with a deep understanding of several >'unrelated' fields of knowledge. Most of us with actual competence >in a certain area are SUBspecialists. This is natural since the >knowledge bases have exploded to become impossible for any one man >or woman to comprehend. An industrial cobol programmer probably >doesn't know shit about Java (perhaps a bad example; I'm not >a programmer, but I know a guy who makes a good living off cobol!) You aren't that far off - at our developer's conference most people didn't know why Java was so hot. Particularly funny since Acucobol users have been getting that compile-once/run-anywhere ability for quite awhile. # Chris Adams <adamsc(a)io-online.com> | http://www.io-online.com/adamsc/adamsc.htp # <cadams(a)acucobol.com> | send mail with subject "send PGPKEY" "That's our advantage at Microsoft; we set the standards and we can change them." --- Karen Hargrove, Microsoft (quoted in the Feb 1993 Unix Review editorial)

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Elliptic curves
by nobody＠zifi.genetics.utah.edu 17 Dec '03

17 Dec '03

The arrival of warm weather is heralded by the pig shit (or whatever kind of shit Intel swines have for brains) getting soft in Timothy C[unt] May's mini-cranium and the resulting green slime seeping through key cocaine- and syphilis- damaged nose and onto his keyboard. ^ ^ (o o) Timothy C[unt] May ( ) \___/ !_!

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Apology
by jc105558＠spruce.hsu.edu 17 Dec '03

17 Dec '03

- James - wrote: >I am writing this ... >Tim May, do >you have anything on subjest to discuss? I apologies publicly for this comment. I'm sorry Tim. My bad. - James -

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Re: PGP in Russia
by jim bell 17 Dec '03

17 Dec '03

At 02:29 AM 12/6/96 -0800, Declan McCullagh wrote: >A slight correction -- taking PGP out of the US is not illegal, as long >as you take adequate measures under the presonal use exception to prevent >your laptop from being stolen by foreign nationals and keep records of >your trip for five years. At least that's what y my friend from the State >Dept told me when we had dinner a few weeks ago. Don't the ITARs say it's illegal to "disclose" that material to a foreign person? If that's the case, then presumably a person could take the material out of the country without "disclosing it," or he could "disclose" it to that foreign person inside the US. True, the government seems to have already taken the position that there is a personal-use exemption, but so far we haven't heard any action with regards to in-country disclosure to a foreigner. I'm not trying to give them any nasty ideas, but a domestic sting with this as its nexus seems possible. Jim Bell jimbell(a)pacifier.com

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Coderpunks
by mixmaster＠remail.obscura.com 17 Dec '03

17 Dec '03

Tim C[retin] May's IQ is lower than the belly of a pregnant snake. His ignorance and stupidity are bottomless. o o /< >\ Tim C[retin] May \\\_______/// // ||||||| \\

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States' crypto legislation
by ichudov＠algebra.com 17 Dec '03

17 Dec '03

hi I wonder whether various states in the US have laws restricting use of cryptography. In particular, does anyone know of such laws in Oklahoma? thank you - Igor.

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