December 2003 - cypherpunks-legacy

Re: Signing pictures -- how hard, how long?
by kqb＠whscad1.att.com 17 Dec '03

17 Dec '03

Alan (Miburi-san) Wexelblat <wex(a)media.mit.edu> said: > The problem with bit-rot is a more significant one. In this case you might > want to compute your hash not over every bit of the image, but over the > "significant" ones. That way if you lose low-order bits that no one cares > about your signature is still valid. If your signature does not include the low order bits of your image, then someone could embed a secret message in those low order bits (via Romana Machado's "Stego," for example) and your signature still would be valid. I wouldn't want my signature over someone else's steganized message. I'm sure there's a simple fix for that, such as ensuring enough bit rot to blow away any but the most error-tolerant steganography or including a disclaimer of responsibility for the low-order bits, but I couldn't resist pointing it out. Kevin Q. Brown INTERNET kqb(a)whscad1.att.com or kevin_q_brown(a)att.com

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MTGS: Conflict Alert
by edgar＠spectrx.saigon.com 17 Dec '03

17 Dec '03

-----BEGIN PGP SIGNED MESSAGE----- If the Cypherpunks schedule their January '94 meeting on the 2nd Saturday, Jan 8, that will conflict with a party announced by visiting Exi fireman Harry (Hawk) Shapiro. Harry said: As I announced a month or so ago, I am holding a party on Jan 8, at the Shearaton Palace Hotel in San Fran. Jan 8th is the last day of MacWorld. Hopefully a group of us will meet for dinner arround 6pm. The party will start about 8 or 8:30. As I doubt either Harry or MacWorld will change their schedules for our benefit, I suggest the Cypherpunks consider (and announce with plenty of lead time) changing theirs to the Saturday after (Jan 15) (The Saturday before is New Year's day). -----BEGIN PGP SIGNATURE----- Version: 2.3a iQCVAgUBLQ3ZId4nNf3ah8DHAQEJ6gP9GnsdIuxnTK2fYDuVKEULDOCnLzBcYJKZ omv6A42BhRjBxDh5qnKbJXjjN7P4rIzsI+0F2GMO/LPyx9IQnTZ9iGJ2Q4hteL97 ueL/BirVX//39mNwmf9DsWej59GEzKUgBbsjv3E14aHsOJhO6wWh9Swg3qZeJJuR fVSWJP3ynCY= =0bKX -----END PGP SIGNATURE----- -- edgar(a)spectrx.saigon.com (Edgar W. Swank) SPECTROX SYSTEMS +1.408.252.1005 Cupertino, Ca

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Re: MTGS: Conflict Alert
by plaz＠netcom.com 17 Dec '03

17 Dec '03

>If the Cypherpunks schedule their January '94 meeting on the 2nd >Saturday, Jan 8, that will conflict with a party announced >by visiting Exi fireman Harry (Hawk) Shapiro. Harry said: > > As I announced a month or so ago, I am holding a party on Jan 8, > at the Shearaton Palace Hotel in San Fran. > > Jan 8th is the last day of MacWorld. Hopefully a group of us will > meet for dinner arround 6pm. The party will start about 8 or > 8:30. > >As I doubt either Harry or MacWorld will change their schedules for >our benefit, I suggest the Cypherpunks consider (and announce with >plenty of lead time) changing theirs to the Saturday after (Jan 15) >(The Saturday before is New Year's day). Actually, there were plans to move the CyPunks meeting to Sat, Jan 15 anyway, since Jan 8th already conflicts with something else (Usenix? something Unix-y). Of course, the 15th is when the ExI-BATF (Extropy Institute - Bay Area Transhumanist/Task Force, for the extropianly-impaired) meeting would normally be held. I think we can ask Dave Krieger to put this off one week to the 22nd. If so, then I'll be happy. What d'ya say Dave? _______________________________________________________________________ Geoff Dale -- insert standard disclaimers here -- Plastic Beethoven plaz(a)netcom.com ExI-Freegate Virtual Branch Head plaz(a)io.com 66 Pyramid Plaza Cypherpunk/Extropian Freegate, Metaverse(a)io.com 7777 "Once you've gone plastic, you can never go back."

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Re: anonymous video rental store
by pierre＠shell.portal.com 17 Dec '03

17 Dec '03

> (A less obvious problem with the scheme is that the store could use > surveillance cameras to identify which tapes the customer selected, but I > chose to ignore that problem.) An other way to cheat would be also to process the returns faster... In the US (California?), since a well known case, (sorry, no bibliographically correct reference is at hand here) it is illegal for video stores to disclose rental records anyway. [Knowledgeable videomaniacs are welcome to fill in detailed references and whether it is illegal to collect such records, or just to misuse them. I seem to remember also that video stores cannot market their customer lists (as mailing lists). Before I spread anymore rumors, anybody knows the details? (It's probably no use asking somebody in a video store, they would be the last ones to know :-) a problem of our current legal system...] In any event, the case of concern when trying to build protocols and hardware for anonymous video rental is when the store personel is dishonnest. There is little point in trying to postpone this consideration. Pierre Uszynski pierre(a)shell.portal.com

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Re: signing pictures
by wcs＠anchor.ho.att.com 17 Dec '03

17 Dec '03

One reason that signing pictures could be useful is so that you could tell that a given picture came from, say, FoobarFoto Mark IV Camera Serial #32767, which lets you know that the photo was digitally retouched after it was taken. Yes, it's easy for someone to transform that into an unsigned picture, simply by twiddling a few bits (doing so at the end of the bitstream lets you minimize any corruption, btw), but you can at least be sure that a signed video or still picture was faked in real-space before digitizing it... and it's easier to detect those fakes, though reputable publications like the National Enquirer and the TV news programs showing exploding cars still have trouble on occasion :-) Bill # Bill Stewart NCR Corp, 6870 Koll Center Parkway, Pleasanton CA, 94566 # Voice/Beeper 510-224-7043, Phone 510-484-6204 # email bill.stewart(a)pleasantonca.ncr.com billstewart(a)attmail.com

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anonymous video rental store
by jim＠bilbo.suite.com 17 Dec '03

17 Dec '03

I couldn't sleep last night and, as is often the case, my brain gets a mind of its own and starts thinking irrelevant thoughts. The irrelevant thought that occupied my brain's mind last night was "anonymous video rental store - Is it possible?" Ignoring for the moment the "fact" that video rental stores will some day go the way of the dinosaurs, would it be possible to structure a video rental store with the following properties: 1) The store could not track which customers rented which tapes. 2) The store *could* tell which tapes get rented and which tapes do not get rented. The store would adjust it's selection of tapes based in this information. (get more of the popular tapes, remove the unpopular ones) 3) The store could some how penalize customers that returned tapes late, or not at all. The nature of the "penalty" is flexible. This implies that the store could somehow verify that the tape a customer returned is the same tape the customer rented, but without discovering which tape it is. (I believe this is the hard part) I have a partial solution. Here it is: The store is arranged like a Blockbuster video store in that there are a bunch of shelves with videos on them. For each video, there is a box describing the video and a variable number of tapes co-located with the box. In a Blockbuster video store, the tapes are in plastic cases that identify the video on the tape. In the AVRS (Anon Video Rental Store), the plastic cases would not contain any identification. However, the tapes themselves *would* contain some kind of identification (stickers with video name and bar code, for example) When a customer enters the AVRS, it (the customer) grabs a random handful of tokens from an "available" bin. These tokens each contain a unique identifier. The customer walks around the store searching for videos. When the customer finds a video, it takes one of the plastic cases (opening it to verify it really is the movie it wants). The customer inserts one of the tokens into a pocket that exists on the outside of the plastic case. The pocket is transparent and the token's identification number can be seen. The customer selects the videos it wants, inserting tokens into pockets. When the customer is done, it returns the unused tokens to the "available" bin and proceeds to the check-out counter. The customer hands the clerk an AVRS id card. The AVRS id card contains information about the customer (TBD). The clerk at the checkout counter scans the id card and the tokens that were placed in plastic case pockets. >From this information, the AVRS knows that the customer identified by the AVRS id card has rented N tapes on a given day. (Actually, all the clerk *really* knows is that the customer has rented N tokens.) The clerk collects some money, the customer leaves with the plastic cases, tapes, and tokens. The customer returns to the store a couple of days later. The customer removes the tokens from the case pockets. The customer places the plastic cases (with tape inside) in a "tape return" bin and places the tokens in a "token return" bin, and then leaves. Periodically throughout the day, a clerk examines the tapes in the "tape return" bin. The clerk opens each case and scans the bar code on the tape. This way the AVRS can track which tapes get rented and which tapes do not get rented. The clerk returns the plastic cases (with tapes) to the shelves. At the end of the day, a clerk collects the tokens from the "token return" bin and scans them. The computer marks the tokens as returned and clears the appropriate customer record. The clerk places the tokens in the "available" bin. ---- The most obvious problem with this scheme is that the store has no way of knowing if the tape the customer returned is the same tape the customer rented. A customer could return a blank tape without getting caught. (A less obvious problem with the scheme is that the store could use surveillance cameras to identify which tapes the customer selected, but I chose to ignore that problem.) The problem to solve, then is: how can the store catch dishonest customers, yet be unable to track which customer rented which video? There needs to be an additional step at the time a customer returns a tape. The store needs to be able verify that the tape a customer is returning is a tape that was rented from that store and is not overdue. The store doesn't need to know what tape it is, or who is returning it, just that it came from that store and is not overdue. If the tape *is* overdue, then the customer must personally return the tape to a clerk and pay a fine. (and risk a bit of anonymity) Perhaps we could embed some electronics in the tape cassette (or sticker) that would enable a clerk to store a signed "due-back" timestamp on the cassette without being able to store any information that would identify the tape. The signed timestamp would have to be transferred through the plastic case, since opening the case would reveal the tape inside. Sounds sort of like a blind signature. Needless to say, it should be difficult for the customer to tamper with the information on the cassette. Any comments or better ideas? Jim_Miller(a)suite.com

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He's Baaack!
by wcs＠anchor.ho.att.com 17 Dec '03

17 Dec '03

Keywords: Detweiler Yeah, one of his tentacles is posting to Cypherpunks again; unfortunately we haven't really decided how to do a good reputation system yet, so filtering out these sorts of attacks without also trashing newbies and causing other collateral damage isn't easy yet. However, I can report that at the December physical Cypherpunks meeting in the Bay Area, Tim May pointed out that *all* the major tentacles were there - Tim, Eric, John Gilmore, Nick Szabo, and Jamie Dinkelacker. Just for fun, I asked Jamie if I could see his driver's license (it's a "real" California license), and Tim, Eric, and Nick also presented theirs. (John was out of the room doing Cygnus business, but I've known him for 6-7 years.) Either they're all separate people, or Tim/Eric/Dr.Moriarty/Jamie/Medusa hired a bunch of actors and got good fake California ID for them. On the other hand, I suppose this just means that *I'm* one of the tentacles now, but I guess that's just a risk you've got to take in the search for Truth, Justice, and the American Way.... Tentacle #9 # Also known as # Bill Stewart NCR Corp, 6870 Koll Center Parkway, Pleasanton CA, 94566 # Voice/Beeper 510-224-7043, Phone 510-484-6204 # email bill.stewart(a)pleasantonca.ncr.com billstewart(a)attmail.com

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RESEND: Re: MTGS: Conflict Alert
by dkrieger＠netcom.com 17 Dec '03

17 Dec '03

At 5:02 PM 12/14/93 -0800, Geoff Dale wrote: >>If the Cypherpunks schedule their January '94 meeting on the 2nd >>Saturday, Jan 8, that will conflict with a party announced >>by visiting Exi fireman Harry (Hawk) Shapiro. Harry said: >> >> As I announced a month or so ago, I am holding a party on Jan 8, >> at the Shearaton Palace Hotel in San Fran. >> >> Jan 8th is the last day of MacWorld. Hopefully a group of us will >> meet for dinner arround 6pm. The party will start about 8 or >> 8:30. >> >>As I doubt either Harry or MacWorld will change their schedules for >>our benefit, I suggest the Cypherpunks consider (and announce with >>plenty of lead time) changing theirs to the Saturday after (Jan 15) >>(The Saturday before is New Year's day). > >Actually, there were plans to move the CyPunks meeting to Sat, Jan 15 >anyway, since Jan 8th already conflicts with something else (Usenix? >something Unix-y). > >Of course, the 15th is when the ExI-BATF (Extropy Institute - Bay Area >Transhumanist/Task Force, for the extropianly-impaired) meeting would >normally be held. I think we can ask Dave Krieger to put this off one week >to the 22nd. If so, then I'll be happy. What d'ya say Dave? Dammit, I specifically picked 3rd Saturdays so they wouldn't conflict with cpunks. Okay, just this once. Remind me at New Year's so I get it right in announcements. dV/dt

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Re: anonymous video rental store
by jim＠bilbo.suite.com 17 Dec '03

17 Dec '03

I'm not convinced a simple anonymous customer/buy-back(or deposit) mechanism is the ideal solution. First, the clerk sees what videos you rent and might be able to identify you from a picture. Second, if the store issues ID cards, then the store can track which videos are rented by each ID. Although the store doesn't know for your real identity, it wouldn't be to hard to find it out in many cases. The clerk coud look out the store window and get the license number of your car. You could avoid some of these problems if the store didn't issue permanent ID cards, but instead issued one-time ID cards. You would get a new ID card everytime you rented some videos. This would make it impractical for the store to automatically track your rentals. This doesn't eliminate the posibility of a clerk remebering your face and pairing it up with a specific rental, or a rental pattern. "Oh yeah, I remember that guy. he usually comes in late Friday night, just before closing. He always rents children's videos. Is he some kind of pervert?" Jim_Miller(a)suite.com

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Re: Improved DH system.
by collins＠newton.apple.com 17 Dec '03

17 Dec '03

Howdy, >I have been told that there is a new improved version of >DH key exchange, which is authenticated. Could >someone give me the reference, and/or tell me what it is >all about?........ Diffie?? I'm back at the office and can (finally) provide the information, sorry for the delay. The paper is "Authentication and Authenticated Key Exchanges" by Whitfield Diffie, Paul C. van Oorschot, and Michael J. Wiener, published in _Designs, Codes and Cryptography, 2, 107-125 (1992), by Kluwer Academic Publishers. Here is some notation, and a brief description of the basic protocol. Almost everything from this point forward is quoted directly from the paper. {.} Braces indicate a hash function. {x, y} is the result when a hash function is applied to x concatenated with y. S_A Alice's secret key for a signature scheme. S_A(x) is Alice's signature on x. S_A{x} is Alice's signature on the hashed version of x. P_A Alice's public key for a signature scheme. If the signature scheme is a public-key cryptosystem, then we define P_A{x} and P_A(x) to be Alice's public key encryption function with and without hashing. E_K(x) Encryption using a symmetric cryptosystem with key K. [...] 5.1. Basic [Station-to-Station] Protocol The STS protocol consists of DH key establishment, followed by an exhcange of authentication signatures. In the basic version of the protocol, we assume that the parameters used for the key establishement, (i.e., the specification of a particular cyclic group and the corresponding primitive element a) are fixed and known to all users. While we refer to the DH operation as exponentiation, implying that the underlying group is multiplicative, the description applies equally well to additive groups (e.g., the group of points of an elliptic curve over a finite field). We also assume in this section that Alice knows Bob's authentic public key, and vice versa; this assumption is dropped in the following section [which I did not type in]. [...] Alice Bob ----- --- a is known, x is random ------------- a^x --------------->> a is known, y is random K = (a^x)^y = a^(xy) <<---- a^y, E_K(S_B{a^y, a^x}) ---- K = (a^y)^x = a^(xy) ------- E_K(S_A{a^x, a^y}) ------>> The paper is a very good read. It describes the motivations behind the protocol; how to assure (or dis-abuse) yourself of the security of other protocols; modifications; other uses; etc. I highly recommend it. Hope this helps, Scott Collins | "Few people realize what tremendous power there | is in one of these things." -- Willy Wonka ......................|................................................ BUSINESS. voice:408.862.0540 fax:974.6094 collins(a)newton.apple.com Apple Computer, Inc. 5 Infinite Loop, MS 305-2B Cupertino, CA 95014 ....................................................................... PERSONAL. voice/fax:408.257.1746 1024:669687 catalyst(a)netcom.com

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