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From: Michael Dwyer (mdwyer, timestreamtech dot com) Date: 2001.03.08 - 16.38 MST
Damnit, man, I'm at WORK right now! Why couldn't you send me this one on a weekend or something... well, not this weekend... Anyway... --- Jay Miller <jnmiller, cryptofreak dot org> wrote: > Okay, so my original "this is gonna be a piece of cake" idea didn't > pan > out. The parity bit business isn't working out. Consider the first > 20 > bits in the thing: > > 1 1 1 1 0 0 1 1 0 0 1 1 0 1 1 1 0 0 0 1 Are we sure we've got the keying correct? The bits come out significantly different if you consider it to be phase-shift or manchester encoding. I need to sit down and stare at it a while, and can't do that right now. :( > Parity just doesn't seem to work on that sucker. And the 'inserting > one or zero to break up a BRK' doesn't apply, either.. Parity is limited to none, even, or odd. That should be relatively easy to eyeball... Should be. Do we know that this is a consumer modem? Is this assured to be on a phone? With more info, we could make assumptions... For instance, since the frequency doesn't change, it isn't FSK, so it isn't a 300-baud modem. PSK looks a bit more reasonable, but it should be noted that PSK encodes 2 bits per transition, so we could be reading it all wrong. They could be using Manchester encoding, but I've never heard of that being used in modem technology, so I would doubt it. Consumer modems generally run [n|o|e][8|7][1|1.5|2], and that should be easy to clock out, right? <sigh> Modems are asynchronous, so there should be some form of clocking in the signal, too -- if not the stop bits. I really have to look at my notes, so I'm mostly just spewing ideas for the rest of you. Good luck. > I was also thinking that any encryption would, it seems to me, have > to be applied to letters rather than bits.. so we shouldn't have to > worry about that. Right? Our first step need to be finding a reasonably bitstream. The encryption is an entirely different problem. That said, I cannot imagine the prof being THAT evil -- I'm looking forward to PigLatin or ROT13. :) More later... __________________________________________________ Do You Yahoo!? Get email at your own domain with Yahoo! Mail. http://personal.mail.yahoo.com/ -- This is the mod-chal mailing list. To unsubscribe, email majordomo, cryptofreak dot org with message body 'unsubscribe mod-chal'. Or, for more information, visit http://www.cryptofreak.org/.
This archive was generated by hypermail 2b30 : 2001.09.26 - 14.03 MDT |
