March 1993 - cypherpunks-legacy

Re: warning to "sci" anonymous posters
by Al Billings 16 Mar '93

16 Mar '93

This is another message on the Cancel Message Generator issue in news.admin.policy. In article <C3tzrs.5t5(a)redpoll.neoucom.edu> Richard Depew <red(a)redpoll.neoucom.edu writes: > As I promised yesterday, I emailed each recent anonomous poster >in the "sci" hierarchy a note explaining what may happen this >weekend. > >Dick >=-=-=-=-=-=-=-=-= >Dear anonymous poster, > > You may not be aware of the discussion in news.admin.policy >concerning the propriety of posting anonymously to newsgroups which >have not invited such postings. As someone who has posted anonymously >to the "sci" hierarchy recently, you should read it. > > I am writing to inform you that if Julf, admin(a)anon.penet.fi, >does not soon block anonymous postings to the "sci" hierarchy, then >I will activate an "Automated Retroactive Minimal Moderation" script >that will cancel postings to this hierarchy from his server. This is >intended to restore the pre-Julf status quo, at least temporarily, >over the weekend. > > Rest assured that there is nothing personal in this. I have not >read your postings, and I have no reason to believe that they were out >of line in any way other than being anonymous. I have nothing against >anonymous postings to groups that have decided to accept such >postings, nor do I object to any newsgroup deciding to do this. I >*do* object to Julf's permitting his server to post to newsgroups >without any effort to determine whether the readers of those newsgroups >want to permit anonymous postings. > > You have several possible courses of action if you wish to post >to the "sci" hierarchy while the "Automated Retroactive Minimal >Moderation" is in effect: > >*1 convince Julf to accept the "Petersen Proposal" for default > settings for different hierarchies. I promise to turn off the > ARMM script as soon as I hear that he will do this (or anything > reasonably responsive). > >*2 convince the readers of the newsgroup to which you want to post > that anonymous postings should be accepted in that newsgroup. > I can think of several valid reasons that may prompt such a desire, > but the decision should be made by the readers of the newsgroup, not > imposed by a single person such as Julf, or me. I promise to > abide by whatever decision the newsgroup makes. This does not > need to be a formal vote. A straw vote with a clear majority will > suffice. > >*3 have a friend post for you, use a different anonymous server, > or, if all else fails, post under your own name. People used to > do this, you know. :-) > > If none of these suit you, then simply be patient, and wait until >Monday. I intend to run ARMM, if I run it at all, for less than 48 >hours... this time. This is merely intended to be a demonstration >that an effective enforcement mechanism for blocking postings from a >particular site can work. > > I apologize in advance for any inconvenience this may cause you. >My argument is with Julf and is about the default setting for entire >hierarchies; it is not with you or your particular postings. > >Sincerely, >Dick Depew >=-=-=-=-=-=-=-=-= >-- >Richard E. Depew, Munroe Falls, OH red(a)redpoll.neoucom.edu >"Leap years are a pain; the earth should be stabilised." - Geoff Collyer > and Mark Moraes in getabsdate.3

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[detecting interesting lines to look at]
by Doug Humphrey 16 Mar '93

16 Mar '93

> And don't tell me they can > build computers that can distinguish between a PGP file transmission > and some > hormone crazed 15 year old dork downloading the latest GIF of Cindy Crawford > or a ZIPed ware. I've looked at hexdumps of GIFs and ZIPs and for all > practical purposes they look about as random as PGP data. If the NSA > can build a parellel computer that scans all the trunks in the U.S. > simultaneously AND can tell the difference between PGP streams and ZIP/GIF > file data streams, then I just might as well go and shoot myself right > now. > >Er.... you might want to get your gun out..... the middle of hexdumps of >GIF's and ZIP's and PGP files may look the same, but the file headers >are quite distinguishing. If you want to hide encrypted data, each >person needs to find their own way of doing it ---- if everyone hides it >in the low bits of a GIF file, it would be very simple for the NSA to >scan GIF files to see if the low bits looked like the header of a PGP >file..... To some extent, this discussion is ignoring the importance of "context". Yes, if you have to do detailed searches of the data traveling down a million lines, you are likely to fail. That is why you don't do it. What you DO is look for things that look out of the ordinary, things that alone would look fine, but within a given context would look wrong, and then search those exception cases in more detail. Example, someone comes up with a way that voice looks just like fax from the data spectrum standpoint. Great, no way that anyone can scan the line and figure out, in the few seconds that they are scanning, that what they are seeing is really voice. So, you attack it by looking at connection records, and looking for what looks like fax machines from the data standpoint, but seems to have a usage record (times of day, duration of calls, time between retrys, etc) of telephones. Remember, even though the technology has changed, the end users of it have not, and the end users are the ones that you are looking for, the ones who are setting up the usage records. So, they now have a catagory of "fax machines that behave like fax machines" and "fax machines that behave like phones". Wonder which ones they will use the Special Equipment on, eh? Same goes for PGP vs. GIFS. The guy moving 4k long GIFS is the guy moving the PGP stuff that looks like GIFS. It doesn't nail all of the possible uses, but this is all a game of the odds anyway, and in the long run the usage patterns, the more meta data, can give people good clues to work with.

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Re: HIDE: embeddin msgs into snd & graphics
by Derek Upham 16 Mar '93

16 Mar '93

> I think Eli is right, too, that lossy compression is pretty much out of the > question for this application. It would be too easy to lose the message > that is encoded in the low-order bits. Uh, unless the JPEG FAQ sheet has seriously mislead me, lossy compression would be excellent for this sort of steganography. In the standard JPEG encoding procedure, an image is broken into square blocks of pixels, eight per side. These blocks are run through a 2-D discrete cosine transform, producing a set of cosine waves that are equivalent to the original blocks (within small errors). If the original image was smooth (a natural image, for example), the low- frequency waves will contain all the information necessary for reproducing the block; the high-frequency waves will contain nothing but faint noise. So the JPEG encoder _dumps_ the high-frequency cosine waves. That's how the format gets a lot of its compression. This is where steganography comes in. Take these empty wave slots and stick your data in them. For example, if the wave magnitudes are stored as four-byte integers, store one byte of data in the lowest- order byte in the slot (or go down to four, two, or even one bit per integer, if necessary; floating-point would be wonderful, here). As long as the hidden data representation looks like very tiny values to the JPEG decoder, the data should be completely unnoticeable on display---but the steganographic decoder will know where to look for it and what to do with it. Anyone have honest-to-god practical experience with JPEG/JFIF to assess the feasibility of this technique? Derek Derek Lynn Upham University of British Columbia upham(a)cs.ubc.ca Computer Science Department ============================================================================= "Ha! Your Leaping Tiger Kung Fu is no match for my Frightened Piglet Style!"

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HIDE (Fnord): Targa-24/YUV/D-xxx and headers
by Seth Morris 16 Mar '93

16 Mar '93

W.r.t. the steganography issue and image files (although I think sound files are probably more useful), Targa-24 images are RGB bytes (triples for each pixel, bottom-left to top-right), and seem appropriate for hiding a msg. They are also widely supported for conversion and function as a nice "device independant" image format (The Stone Soup Group's PicLab does a good job on them, IMHO). Does anyone know anything about YUV format? Also, DYUV or some other delta compressed format seems good. If a pixel changes by one more or one less than it "should" the image simply looks like a mediocre scan. Hmmm..... FLI is a delta format... is it appropriate? So... can someone whip up a utility to strip the PGP header and then perfoem some simple filtering (^= with some magic numbers, perhaps, or with some function of the preceeding bytes? Can this eventually help recover a better image, if that could ever be important? I don't think so) and tack on a valid Targa or other header (or correct any headers on images we've slid into). I just started a new job and am swamped, or I'd have written first and posted later ;-) . Seth morris <seth.morris(a)laUNChpad.unc.edu>

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HIDE: embeddin msgs into snd & graphics
by Hal 13 Mar '93

13 Mar '93

The considerations that Eli mentioned make it clear that embedding data in the low bits of an image is not as trivial as it sounds, with commonly-used image formats. In the case of GIF, Eli points out that you may have a 256 entry color table, with each pixel indexing into that table. Flipping the low bit of a pixel may lead to a completely different color. What you could do is to renumber the color table so that, to the extent possible, every even-numbered color has some odd-numbered color that is similar (close in color space), and vice versa. Then rather than just altering the low-order bit of each pixel, you'd change the color of that pixel to be the nearest color of opposite even-odd-ness. For the decode step, though, you could still just check the low-order bit of the (uncompressed) image. That renumbering step sounds like the tricky part. I think Eli is right, too, that lossy compression is pretty much out of the question for this application. It would be too easy to lose the message that is encoded in the low-order bits. Images that would be good candidates for this would be natural, scanned-in pictures. Hand-drawn artworks and most computer-generated images would not have enough natural randomness to allow the message to be slipped in unnoticeably. Fortunately, nudes would fall into the useful category, and they make up a large fraction of the images people exchange. Hal 74076.1041(a)compuserve.com

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Re: Cypherpunks know they're cool
by Marc.Ringuette＠GS80.SP.CS.CMU.EDU 13 Mar '93

13 Mar '93

> Hmm..... how is this alike, and how is this different, from a hardliner > NRA saying, "We should ask people to protect themselves by wearing > bulletproof vests, instead of trying to ban guns"? Ted, please don't be a bonehead on purpose. I bet you can see the difference between some bits coming down a wire and a bullet coming at you at 1000 feet per second. It has to do with the level of threat and the feasibility of protecting yourself. > As long as we are really being freedom-loving, there's nothing we can do > (or should _want_ to do) to get people to attend groups that allow > anonymous posters, if they only want to travel in "real person only" > circles. Not true at all! Just because I like freedom doesn't mean I shouldn't try to convince people to act in a way that is more freedom-loving. -- Marc Ringuette (mnr(a)cs.cmu.edu)

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CYPHER: Plain encypher
by Matthew J Miszewski 13 Mar '93

13 Mar '93

In response to all those interested in disguising messages in complicated graphics/sound/random # generators/etc I believe this would unnecessarily defeat the purpose. TLA types become suspicious when they see random pgp type data transmissions flying across their screens. When they get one of these monsters, they of course attempt to decrypt it (assuming its from someone they wish to monitor (All of us?). They also become suspicious when incredibly long plain text transmissions are broadcast. It seems desireable to have a mode of encryption that will encrypt my message and then package it in a short (relatively) plain text message. The NSA/CIA/FBI wont bother trying to decrypt messages that are the equivalent of 'My slide show of my trip to Florida". And even if they were to suspect, or by some miracle decrypt it, you have your Plausible Deniability. Make the message generator sufficiently general that all final messages are plausible real messages. Only those expecting a message that is encrypted in plain text will know they have one. They would have the key to decrypt it. And no one would be the wiser. Matt mjmiski(a)macc.wisc.edu

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Re: HIDE: embedding msgs into snd & graphics
by blojo＠sting.Berkeley.EDU 13 Mar '93

13 Mar '93

> I think color images, as opposed to mapped, would be the way to go > for steganography. More room, and nobody expects them to compress. Yeah; but even if we're talking full 24-bit images, we're going to have problems. Once 24-bit displays become standard, I really doubt that there will be many images stored in a non-lossy format. And once you try to hide data in a lossy encoding scheme, you run into a lot (though not all) of the problems you have with colormaps. It would be a lot easier to hide data in an image if one had a control-image (the original) as well as the altered-image (the one holding the message), but this defeats half the niftiness of trying to do things this way. > Eli ebrandt(a)jarthur.claremont.edu -J.

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An Appeal to Calm
by tcmay＠netcom.com 13 Mar '93

13 Mar '93

Folks, Tempers have flared. Angry words have been sent out to the list. We've all been mail-bombed by an angry member of the list (who wants off--NOW!). I guess this is our first real flame war--now we're a real mailing list! But let's not let the current controversy confuse our very real mission, nor hide the progress we've seen so far (remailers, spread of PGP, experiments with digital cash, etc.). If we let the list self-destruct through a few unfortunate incidents, all hope is lost. * The "unsubscribe" problem will hopefully soon be fixed. Maybe an automatic handler (like "majordomo," someone suggested) can be installed. * Mailing lists like this one characteristically have wildy fluctuating traffic levels. No messages for a couple of days (leading to "Is the list broken?" queries) and then 50 messages in a single day (leading to "Enough already! I can't take the volume." messages). Remember, it is the list membership that is generating the volume, not the list management (such as it is). * Some have said the "cypherpricks" list is generating all noise and no signal. Many of us would disagree. Actual code is being written, deployed, and experimented with. One bunch is helping with PGP, another is writing and deploying remailer programs, another is pursuing steganography (hiding messages). Pretty impressive. Especially for a new mailing list. * And relatively little flaming is going on. The closest we've come to a real act of malice was the mail bombing of the list by a disgruntled member--I won't go into that further. * There are serious issues involving the uses and abuses of these various tools and capabilities. Anonymous postings carry obvious concerns. So does untraceable electronic mail, with the potential for extortion threats and even fully-secure markets for assassinations and other crimes. Some of these issues have been discussed on the list. No doubt some see these debates as "noise." Well, a mailing list cannot of course only cater to one particular set of needs. * If we don't discuss these kinds of issues on this list, who will? The FBI and NSA undoubtedly. So why not we the people? I hope things can calm down a bit. -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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Re: Cypherpunks know they're cool
by Marc.Ringuette＠GS80.SP.CS.CMU.EDU 13 Mar '93

13 Mar '93

Ted Ts'o writes, > What I don't understand is, why are people complaining? We're just > seeing people exercise their sacred right to free speech..... all over > this mailing list. After all, isn't this what you were working towards? Heh. I agree with Ted. Try taking the same advice we'd give someone who received a offensive anonymous note: quit your bitching & moaning, you losers! Yeah, yeah, I know, volume attacks are of a different kind than offensive content. But my own belief is, if our software is broken, we shouldn't blame the doofus who comes along and tickles it. If we end up having a problem of volume harrassment, we should expect to have to PROTECT OURSELVES with some half decent mailing list software. For instance, something that accepts mail only from subscribers or that shunts large messages (or excessive number of messages from a single person) to the moderator for review. The fact that we have stupid software is our own fault. To me, this has the same feel to it as the current flap about anonymous newsgroup postings. The right answer, in my opinion, is to use news distribution software which can filter out anonymous postings (and, in order to enable that, and prior to the availability of "real person" cryptographic certificates, to ask that all remailers provide a special header line). What these solutions have in common is that we ask people to protect themselves, rather than requiring everyone else to adhere to their notions of good behavior. Which brings to mind the potential problem that 99% of everybody may choose to participate exclusively in "real person only" groups. Any hints at a solution to that one? How about if we try to convince people to participate in "pay as you go" groups using digital postage? That would solve many of the problems, in a way that is less offensive to the freedom-loving among us. -- Marc Ringuette (mnr(a)cs.cmu.edu)

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