- cypherpunks-legacy@lists.ogf.org

Tagging data to detect thieves
by Hal 12 Mar '93

12 Mar '93

Mark Ringuette asks about schemes to detect which copies of some proprietary information were used to resell the data. I recall reading a paper on this in the proceedings of one of the crypto conferences within the past several years. Unfortunately, I don't have a more accurate reference handy. The authors referred to this problem as "digital fingerprinting" (i.e. adding a "fingerprint" to each copy of a document). As I recall, the idea was to twiddle bits in such a way that any subset of copies up to a specified size would have a certain number of identically twiddled bits. The thiefs who cross-correlate 64 (or however many) copies will not know about the bit twiddles which were common to all 64 copies. Their output will still contain those common bit-twiddles, and this information allows the thiefs to be caught. The paper shows a formula for the number of possible bit-twiddle-places and the number of bit-twiddles per copy needed, as a function of how many copies you are defending against the bad guys getting. It was basically just a combinatorial/counting argument. I do seem to recall that if the bad guys could get a lot of copies the number of bits needed grew exponentially. I don't know whether defeating an attack with 64 copies was practical using this scheme. Mark also asked about secret sharing. The classic secret sharing paper is "How to Share a Secret"; I think it was by Shamir, in an old CACM from the 70's. As I recall, he proposed encoding the data as a K-1 degree polynomial in some modulus field. Give each person a point on the polynomial. K points are required to recover the polynomial. I don't recall how the encoding of the data as a polynomial was to be done, but the author showed that K-1 points gives you no information about it. Hal 74076.1041(a)compuserve.com

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Re: HIDE: embedding msgs into snd & graphics
by blojo＠sting.Berkeley.EDU 12 Mar '93

12 Mar '93

> I would have it take a GIF file and a > binary file to be embedded, and produce an output GIF with the low order > bit of each byte changed to be the next bit of the embedded binary file. I've been thinking about writing this too, but, alas, I have been too busy. If you write this program, I would encourage you to support encoding/decoding in more than just GIF files. My main reasoning behind this is something like: if there is one piece of software that is commonly used to hide data in noise bits, and it only supports one format, then things in that one format are automatically suspect-- it's almost as bad as not hiding the data. I'd encourage you to support JPEG and sunaudio formats (though the info density one could store in each of these is probably a lot lower than what you could pack into a GIF), as well as some less-used formats like tiff and rast. Hmm... and if you can figure out how to pack a useful amount of data into an XPM, I'll be really impressed. I don't know if you actually know GIF format (I don't) but I know that you'd have to do some reasonably intelligent churning of the data. For one, it's just not going to be as easy as dropping a noise bit from each n-byte set; GIF format is fairly compressed as I understand. Also, if you're not careful, you'll end up with a picture that chokes displays after encoding that worked fine before encoding. (Many machines have 8-plane displays, which means a 256-color colormap. If you mess with the noise bits on a GIF that has 200 colors, you're going to come up with one that has 400 colors. Many display programs (like xv) will compress the colormap when they see this; the X server will also slide colors together when you allocate things and the map is full. BUT, such high-colormap-size gifs would basically have "I AM A CONTAINER FOR ENCRYPTED DATA" tattooed on the backs of their necks. -J

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Re: CYPHERPUNKS=EMAIL HARASSEMENT?
by Mark C. Henderson 12 Mar '93

12 Mar '93

-----BEGIN PGP SIGNED MESSAGE----- Subject: Re: CYPHERPUNKS=EMAIL HARASSEMENT? On Mar 11, 21:16, Michael Brennan wrote: } Subject: Re: CYPHERPUNKS=EMAIL HARASSEMENT? } } Brushing this matter aside as a non-issue and pretending there is no } problem will not make the problem go away! UNSUBSCRIBE REQUESTS SENT TO } CYPHERPUNKS-REQUEST ARE BEING IGNORED!!! Well, sending a 3000 line file to hundreds of people, wasn't the correct response to the situation. But, to add something constructive, why don't we use majordomo to handle list additions and delections automatically? Mark - -- Mark Henderson mch(a)squirrel.wimsey.bc.ca markh(a)wimsey.bc.ca -----BEGIN PGP SIGNATURE----- Version: 2.2 iQCVAgUBK6A2sPfE/ap/JEqpAQEK6AQAqejFaX3122HwrkLibTYr/rEGEoL6qpSv sSn2oVxoOJXc+R52P8RCZzfp/X0O5tp92tUf4sAL2YKIlb72W2y9rXZ9TXMxpmxi AgRqqpts1uoKAfUMBaM9Lr0QJ2V7fnMRjOJiu2mU/bSbC4Tzr15reKjmhkQDDZXo FoybTVchSEw= =3DYZ -----END PGP SIGNATURE-----

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Re: HIDE: embedding msgs into snd & graphics
by tcmay＠netcom.com 12 Mar '93

12 Mar '93

Matt Thomlinson writes: >The idea of using a DAT tape as a mode of transport, however, doesn't >appeal that greatly to me. To send a message, I have to pull out one of my >prevoiusly recorded DAT host-tapes, then record over the 5th song with my >mix of host/message pair, then fed-ex it (or hand-deliver it) to my >target. If I take this signal and push it across internet, I no longer >have the passive-looking DAT tape in my DAT music collection. Instead, I >have a 900k sound file that I push across the net. Since the net is >usually not used to push the latest Michael Jackson tune, it might raise a >flag. > >Tim's comments are valid and definitely help solve problems on the >physical level: now how about cyberspace? Granted, a DAT can carry more data in the LSBs--about 80 MB, about the length of 10 Bibles--than one really needs. The GIF option I mentioned allows a widely disseminated image file to contain about 32 KB in just the LSBs of a 512 x 512 x 8-bit gray scale image. A color image could easily hold three times more (LSBs in each color channel). And some GIFs are much larger than 512 on a side. So, a fairly long message could be inserted into the "noise floor" bits of a scanned or frame-grabbed image, or of a piece of "original art" and then posted worldwide in one of the GIF groups. Who knows what evil messages are even now being sent in GIFs of Cindy Crawford and Claudia Schiffer? Use your imagination and you'll see there are several other easy ways to hide messages. (Again, we're talking steganography--check the "Glossary" in the soda.berkeley.edu archives if this is new to you.) -Tim May -- Timothy C. May | Crypto Anarchy: encryption, digital money, tcmay(a)netcom.com | anonymous networks, digital pseudonyms, zero 408-688-5409 | knowledge, reputations, information markets, W.A.S.T.E.: Aptos, CA | black markets, collapse of governments. Higher Power: 2^756839 | Public Key: MailSafe and PGP available.

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CASH/BANK: combo
by Karl Barrus 12 Mar '93

12 Mar '93

-----BEGIN PGP SIGNED MESSAGE----- Hal saw through my laziness attempt: I thought it would be "easiest" for a cash accepting remailer to increment an account (marking bills as spent) and have users request more bills from the bank rather that filter requests through me. However, this does lead to a perpetually full bank account... But actually, a full service bank isn't required (although maybe that would be nice) - all that's really needed is for the remailer software to compare the included digicash versus a spent cash list and a valid cash list. The banking portion need only be one command for me to use: one that deposits newly created cash into the valid cash list. When a letter arrives, the digicash is checked, added to the spent cash list, and re-routed. For privacy, requests for digicash could come to me via anonymous remailers, along with the appropriate header to allow me to respond. This would render logs relating digicash and user useless, since I wouldn't know who is requesting digicash bills. On the other hand, somebody could store up several digicash bills by routing their request through the various remailers. But I'll accept that risk, hoping that nobody on this list would prepare a email attack (except for the unfortunate folks who can't seem to unsubscribe :-) JUST KIDDING!!) /-----------------------------------\ | Karl L. Barrus | | elee9sf(a)menudo.uh.edu | <- preferred address | barrus(a)tree.egr.uh.edu (NeXTMail) | \-----------------------------------/ -----BEGIN PGP SIGNATURE----- Version: 2.2 iQCVAgUBK6Ap24OA7OpLWtYzAQHZQAQAo2ofd6lPBx/7XMR3Jr+7G2atMzevNcj3 Wtdrjr1GQJ+15z9duu3vh3yyV4j0rswyJlqp3eJZPCcb1NgEeKVZ1pP54YjDRwL2 UOKcHD55g+SIckIYVE+VFo4s2Ha8CKgtRgHmRV6+MJgiheBBOaOQxjFqRMpru3pO fE9mYRkNUII= =NyB0 -----END PGP SIGNATURE-----

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Cypherpunks know they're cool
by Marc.Ringuette＠GS80.SP.CS.CMU.EDU 12 Mar '93

12 Mar '93

Hey, man, we're the cypherpunks. We're too hip to worry about a trivial little mail bomb. But if we did get upset...well, who do you think has the bigger arsenal of dirty tricks, him or us? Heh. Marc p.s. I'm being interviewed by a campus radio show, regarding cypherpunk-related stuff. I'd welcome any suggestions on topics to bring up, or ammunition to add to my pro-privacy and pro-anonymity arguments. Send them directly to me and I'll summarize to the list.

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Re: HABRECHT=EMAIL HARASSEMENT
by ghabrech＠ultrix.ramapo.edu 12 Mar '93

12 Mar '93

A pesk, me? Ha! The only reason I did it was because I asked a month ago, politely, to be taken off and every day I still have a ton of junk messages in my mailbox. The other person (Name cut off in reply) was right. I'm sick and tired of reading some news about bullshit. I mean it seems that some people have been writing in whenever they have to take a crap. Some of the articles are excellent, some ok, but when you have to weed through 20-30-even 40 messages to get one or two good ones it's just not worth it. Therefore I wish to be taken off. If, in a while, things get straightened up I may resubscribe but for now, I don't have the time. George (The E-mail harrasser) Habrecht ghabrech(a)ultrix.ramapo.edu (for those who wish to mail my mailbox.... I'll nuke it anyway :) ).

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[CRYPT: Dingaling Denning & random # generators]
by Doug Humphrey 12 Mar '93

12 Mar '93

>As I posted once to sci.crypt: encrypted communication is virtually >interchangeable with and indistinguishable from communication itself. >How does someone `know' that you are encrypting a message? This is not strictly true. While someone might not be able to tell that you are engaged in the act of encrypting a message, the transmission of encrypted communications is often detectable. Spread spectrum transmissions often look like an increase in the noise floor of certain communications channels, prompting systems to think that there are malfunctions, and to dispatch someone to take a look at the facility. If they throw a spectrum analyser on it, it doesn't look like valid data in most cases, just noise. With voice communications it is easy to recognize the patterns that speech generates, and they look very different from the randomness that simple crypto produces. Unless one uses a post-crypto wave shaper to simulate the amplitude changes that speech produces, it is simple to build a circut that can make a pretty accurate evaluation of voice/data/crypto going by it. Nothing more difficult in 1993 than was the first 2600 hz detector circut when it was put into widespread production use in the phone network. In fact, given that modern switches are already digitizing the signals, a little DSP hardware should make quick work of the first cut, narrowing down which lines should receive harder evaluation to see if people are trying to protect their privacy. >To do something like have completely tappable communications, we'd need >half the country to monitor the other half, to make sure nothing out of >context is going on. You under estimate some technologies ;-) >Only problem with this is, who monitors the monitors? Who watches the watchmen? >No, I don't buy that paranoid plop about how it would be "trivial" to >set up filters that "detect" encryption, or that this is happening on a >widespread scale by the NSA in the U.S. This is an absolutely absurd >claim. It would not be trivial. On the other hand, an order allowing the modification of the entire telephone network to allow the FBI to have "most-favored-wiretapper" status is also non-trivial, and some are trying to make it happen. >These mechanisms could be just as trivially defeated (although >a-priori knowledge of their function may be required). People who >think encryption is different from communication think that symbols are >different than letters. Speaking as a programmer, good luck explaining >it to a computer. Maybe you over-estimate technology here. We are not talking about breaking crypto here, just detecting it. By its nature it changes the overall composition of the data. Randem data still looks random, it is true, but a phone call represents a certain context, and within that context there is an expected behaviour pattern (or ten or twenty behaviours, but it makes no difference). Within the context, it can be easy to see the change that crypto brings, unless there are active means taken against it. Doug

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HABRECHT=EMAIL HARASSEMENT
by tcmay＠netcom.com 12 Mar '93

12 Mar '93

<<PLEASE FOLKS! Don't "mail-bomb" this or any other list with humongous files!!>> Michael Brennan writes: >Hopefully my subject line got someone's attention. >I just received a 3K file in my mailbox from George A. Habrecht with >lines repeating over and over "Please unsusbcribe me!!!" Perhaps many >of you simply deleted it without even noticing what the mail said. But you >should all take note that the cypherpunks list is starting to piss off > a lot of people who would be supportive of what you are doing if not >for the huge volumes of unwanted mail. ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ (My mail reader said nearly 80 kilobyes...perhaps your figure was in _lines_?) I don't know what the delay has been in unsubscribing people. As always, send requests to the list maintenance address, "cypherpunks-request(a)toad.com". The list manager, Eric Hughes (hughes(a)soda.berkelely.edu) has been away at the CFP conference this week...perhaps this is part of the delay. In any case, the 80 KB (according to my mail reader, Eudora) file was sent by George Habrecht, and was not "caused" by Eric Hughes, nor was it caused by "the cypherpunks list." So lighten up on this point, will ya? >Loading up peoples mailboxes with unwanted mail is IRRESPONSIBLE! >Is this what cypherpunks wants to become known for on the net? It's really >Don't any of you cypherpunks think that maybe sending huge volumes of >unwanted mail to people is innappropriate? Don't you think that maybe >someone should get their act together and rectify this situation?!!! Huh? Like I said, it was Mr. Habrecht who sent the "huge volumes of unwanted mail" and not the Cypherpunks list (unless you're advocating that someone screen postings for content and length?). So if you're angry at getting an 80 K file, be angry at Habrecht. His frustration at having to wait some extra time to get off the list is no excuse for mail-bombing a couple of hundred people! The average Cypherpunks message is about 3 KB, or about 4% of Habrecht's message. With about 25 Cypherpunks messages a day (I'm guessing), Habrecht equalled the average list volume in his angry action. If there are 200 subscribers, then he caused roughly "200 list-days" of mail to go out to readers...all because he couldn't get off the list exactly when he gave the order! As for the average mail volume...well, it is fairly light compared to some other mailing lists. And it is not the list manager who determines the volume, it is of course the list members. The list software simply "reflects" incoming messages to the distribution list...if people write a lot, a lot goes out. Q.E.D. As Sinbad O'Connor would put it: "Know the real enemy." -Tim May P.S. What I did was to _reply_ to Mr. Habrecht, explaining the situation. I attached my reply to a *quoted copy* of his message AND MAILED IT BACK TO HIM! (Actually, my mailer splits incoming messages into 24 KB pieces, so I only mailed one of these back to him....he got off lucky. If several more people do this, he'll think twice about mail-bambing a list again.) -- Timothy C. May | Crypto Anarchy: encryption, digital money, tcmay(a)netcom.com | anonymous networks, digital pseudonyms, zero 408-688-5409 | knowledge, reputations, information markets, W.A.S.T.E.: Aptos, CA | black markets, collapse of governments. Higher Power: 2^756839 | Public Key: MailSafe and PGP available.

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UNSUBSCRIBE ME!!!!!
by ghabrech＠ultrix.ramapo.edu 12 Mar '93

12 Mar '93

DAMN!!!!! UNSUBSCRIBE ME ALREADY!!!!! GHABRECH(a)ULTRIX.RAMAPO.EDU ghabrech(a)ultrix.ramapo.edu

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