December 2003 - cypherpunks-legacy

Re: crypto technique - error
by Karl Lui Barrus 17 Dec '03

17 Dec '03

Argh! I made a math error reducing one of the terms. g and g' do yield the same answer. Whew, I thought something was messed up :-) Karl

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Re: Photocopying money
by catalyst＠netcom.com 17 Dec '03

17 Dec '03

>It's the same chip that's used in vending machines to scan dollar bills. To my knowledge, vending machines don't do optical recognition. They have a pair of photo-sensors, it's true, but these are used in conjunction with tractors only to measure the bill. Another sensor decodes the magnetic ink to determine validity and denomination. I saw this demonstrated recently on a PBS science program. 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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re:backing
by F_GRIFFITH＠CCSVAX.SFASU.EDU 17 Dec '03

17 Dec '03

>workable barter currency? Aug/Sept 93 Mother Earth News has an article "The Ultimate Barter" about "A currency based on time-hours is a boon to a rural community." >poorly-backed digital currency will win out over e.g. U.S. dollars? Depends on legal tender status (see post by Perry). Note too his point that digital currency needn't be poorly backed. However, also note that government issued dollars would circulate in preference to gold backed digital currency issued by someone else according to Greshams law (which was stated in reference to metal coins, but applies to other forms as well). Solution might be to denominate digital currency in something other than $ (e.g. gold grams) & have parallel monetary system develop.

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Re: crypto technique
by Karl Lui Barrus 17 Dec '03

17 Dec '03

-----BEGIN PGP SIGNED MESSAGE----- Well, I couldn't resist trying to find A, B, C, D, E, F. You may be on to something, Matt. The equations are underspecified, and have many solutions - here are some I generated (any of them match what you picked? :-) > 103 110 10 1 51 139 > 103 156 251 1 151 19 > 103 169 254 1 157 43 > 103 72 17 1 191 195 > 103 111 5 1 209 99 > 103 1 18 1 237 203 > 103 202 16 1 251 187 > 5 237 10 5 43 139 > 5 201 4 5 99 91 > 5 64 3 5 113 83 > 5 200 23 5 129 243 > 5 62 8 5 173 123 > 5 164 21 5 185 227 > 5 198 12 5 189 155 Maybe you could look at what these alternate solutions are - it could turn out that the mod operation creates extra valid solutions, which would be quite undesirable. But then, without the mod, the equation may be too easy to pick apart. Or maybe there is some other attack I haven't thought of or don't know about. -----BEGIN PGP SIGNATURE----- Version: 2.3a iQCVAgUBLMXDk4OA7OpLWtYzAQH/YwP/aTP4NwJ257A7GT1iWk7uhCYNEyJGTnkK UrEm0Pw2n1yq3bMwzEem2EPbK+XOIzP1ql0VdgpLOyQ+7quMGWl1+IKY9Ht7wd2J cy0ynJm8N1BZiJjJ2GHza+jAlqsOeVOICyT7f6Jxf/RU79/KSGQ/Jb0j52sHgrEi LfIBPXZueUc= =nzmt -----END PGP SIGNATURE-----

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Re: Backing
by baumbach＠atmel.com 17 Dec '03

17 Dec '03

Isn't a finite source of backing a problem since it rewards those who hoard it? Also If neither Alice or Bob have a backed currency, does that mean they cannot trade? It has always frustrated me to see poor people stay poor, because they believe they have to get their wealth from someone else. People can create their own wealth. A currency that ignores this possibillity seams bad to me. Has anyone invented a workable "barter currency"? Can I.O.U.'s be created such that they work like money? Peter Baumbach baumbach(a)atmel.com

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Photocopying money
by I still don't know your name, stranger. 20-Oct-1993 1925 17 Dec '03

17 Dec '03

>It's true. Canon did indeed create such a chip. It's the same chip >that's used in vending machines to scan dollar bills. They built a >prototype copier which prevented copying money, but I don't know if they >actually decided to install the chip in all their assembly-line >production copiers or not tho. Nope. There is no "chip" that scans dollar bills. Dollar bill scanning is based on the magnetic ink in a few simple stripes, the presence (actually, absence) of UV fluorescent inks, and not on optical recognition per se, and besides, we all know how "reliable" such machines are. NOT! Besides, even if a pattern-match chip existed that could do it fast enough, simply turning the bill a few degrees (say, 45 degrees, across the glass) would render the problem intractable... And how about adding a background of stripes... something to really confuse the chip.... Sorry, no. -Bill

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Re: Paper Shredders
by koontzd＠lrcs.loral.com 17 Dec '03

17 Dec '03

Having been an AFSC 30670 (Electronic and Cryptographic Equipment Systems Technician), and been assigned in hazardous areas you use document destroyers on paper stuff - glass vials with grenade fuses). Equipment destroyers were 35 lb thermite charges, designed to sit on top of a standard piece of equipment in a 19 inch relay rack. I had orders to Iran but got diverted when the Shah fell. The liquid in the document destroyers was clear, and we got to set one off for demo purposes twice a year (never did get to set off thermite, though). Had a one acre room half filled with crypto, thermite would have brought the roof and lots of airconditioners down. All the key cards were treated with lead acetate, they would burn without leaving anything but a greasy wisp of ash.

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subscribe
by Gregory W. Kamen 17 Dec '03

17 Dec '03

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Re: Paper Shredders
by owen＠autodesk.com 17 Dec '03

17 Dec '03

> Stanton McCandlish says: > > > Does anyone know of an AFFORDABLE shredder that really destroys documents > > > by cutting them into confetti, rather than the easy-to-reassemble strips > > > that the typical shredder does? > > > > Yeah, it's called fire. > Fire is, of course, an optimal solution, and those of us who live or > work in a building with a fireplace or incinerator would do well to > use it. However, its hard to spend every day burning things, and > besides that, many of us live and work in urban areas where fireplaces > and other places you can burn large numbers of papers are rare. The > question is thus not out of place. brings back ugly memorys of burn detail, back when I was stationed at a SAC command and control post up in the mountains near Westover AFB. Every scrap of paper that was discarded had to be incinerated, and we rotated through a schedule that made sure everybody got their chance to share the experience. > By the way, the standard method for destroying embassy documents in > case of siezure (not done during the Iran hostage crisis) is > reportedly Thermit grenades. (Thermit would likely reduce a filing > cabinet to slag in moments.) Sounds to me like an enterprising pyro could have a nice little operation, contracting with individuals to burn or blow up their sealed bags of trash. I understand that Beavis and Butthead might be looking for a new job, hey the little weinerheads might amount to something after all! :-) LUX ./. owen

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Re: crypto technique
by Karl Lui Barrus 17 Dec '03

17 Dec '03

-----BEGIN PGP SIGNED MESSAGE----- Another possible problem with the technique is that the multiple solutions are all valid. For example, with two nestings and a = 11/2, b = 8, c = 25/2, d = 3, P = 16 I obtain g = 903 + 4675/4 x + 3025/8 x^2 mod 16 g' = 7 + 3/4 x + 81/8 x^2 mod 16 where the g' is obtained from g by reducing the coefficients mod 16. Solving the resulting equations yields two solutions: a = 11/2, b = 8, c = 25/2, d = 3 (what I chose) a = 31/2, b = 6, c = 17/2, d = 2 Plugging in the second solution: h = 359 + 6851/4 x + 16337/8 x^2 mod 16 h' = 7 + 3/4 x + 81/8 x^2 mod 16 Notice that h' equals g'! So the other solution can be used to form the same polynomial (which we already saw doesn't encrypt uniquely). Can this other solution be used for decryption as well? I'd check but I've REALLY got to go study now :-) -----BEGIN PGP SIGNATURE----- Version: 2.3a iQCVAgUBLMXZsYOA7OpLWtYzAQFjMAP/Si1RuZjfnBNjLauB20rXaUXQMQqyiWBU n/ur7ckXSEmWnADYQqZqCy1tb/+vf5zThQD2IpbF5IH8roxYG99nZQBvvtZAQfEO 3EdbM1esMTS/I0DwcLqkuG26GNNWYGZWi8MQ/0+eXfMa9BXZvkDTuuVBzzHBSXxW 84CVKvitZ68= =FeJW -----END PGP SIGNATURE-----

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