From: hfinney@shell.portal.com (Hal Finney) This homophonic cypher sounds interesting. If the authorities demand your keys, you could scramble each row of the matrix (scrambling each row separately), so that only the dummy message can be recovered.
hmm.. how about rendering the document as a bitmap (or other picture format), uuencode it ( or something similar with encryption of its own ) and then interleaving the ascii dummy message with the ascii of the uuencoded picture before applying this scheme.
Real ascii messages have a character set of about 2^6, so the actual size of the key matrix will be 2^12, and that means that each entry will be about 12 bits. For full generality in handling binary data the character set would be 2^8, meaning a matrix of size 2^16 entries with each entry being 16 bits. This is a 128K byte key, which is pretty cumbersome. Also, the cyphertext is twice as big as the plaintext, which will stand out too.
right, so some kind of squeezing it down one more time maybe ? :-)
Plus, once the authorities see your decryption algorithm it may be pretty obvious that it was designed for this specific purpose, and whatever pressures they applied to make you reveal the key may now be redoubled until you reveal the "real" key.
In all seriousness, we are rapidly approaching enough multimedia saturation that we will also have sound file formats, picture file formats, animation and video formats which can all be used as vehicles for homowhatever schemes. Have a text to speach application record your words into a sound file format, and apply some of your crypto wizardry to make it into weird music, use rhythym tracks mixed in as convincing cover and maybe some harmonic riffs as a red herring to keep snoops from realising that the file might not be what it seems to be. how about encoding real time video signals used in desktop vid-conferencing. and slip encoded documents into the picture as colorful border graphics. Govt snoops tend to act out their information gathering rituals like squirels that have eating disorder, they can't find enough empty holes to fill with nuts (ie: important data ) that they might need to analyse later. so instead of trying to be elegant, be pigs. Bloat your content with obfuscated bric a brac, and banal tracts on technical issues that put hard core nerds to sleep. Our net-universe has vast resources to tap for source material to be used this way. Solid Engineering technique and clever hacks applied to your method, will probably leave trails and artifacts that another crypto engineer can smell! Apply art, and be eratic in order to facilitate keeping your adversary off the track he expects to find. ----- ------ ----- In a previous incarnation, I lived in a house on the same piece of land as an individual who was suspected of engaging in illicit horticultural activities. It soon became evident that my phone was also being monitered. Silly bastards couldn't get anything straight! I actually got a call inquiring about a person with his first name and my last name. :-) and then a day or so later my phone rang and when I picked up the receiver before I said anything I heard the sounds of a dispatch center, and then a womans voice chirped. "operations- may I help you" I replied... *uh... you called me*. she hung up abruptly. It would almost be humorous if they weren't so clueless as they waste our tax dollars in their characteristicly inept fashion! anyway, I gathered that their recorders operated automaticaly, so I took up the habit of dialing into my VAX at work, and playing rogue for hours and hours. Bet somebody made overtime while they assaulted their eardrums with the modulated hiss representing my little ascii hero getting lost in the maze of twisty little passages that all look the same.
A one-time-pad has the advantage that the key is the same size as the file, and there is no size expansion in encryption, plus it's a plausible approach to use for high-security encryption. It will take less space and still allows for multiple decryption.
so .. the dummy file you pad with, you'd just have one? or do you mean you'd make a new one each time? it would get pretty obvious if the same file kept popping up . I guess you could claim to have obsessive compulsive disorder and that this file is your obsession? If you really want to buffalo them you would need an intelligent agent application to compose dummy text for padding that would be reasonably unique each time. I would think that if you could write such an agent it wouldn't be much more work to have it encode whole words with other whole words and apply some linguistic formula, leaving the encrypted file looking like an ordinary, and uninteresting file. It might even be fairly simple to apply a word exchange scheme similar to the classic mentalists routines before encrypting the file, thus obscuring the meaning while still allowing the gestapo to feel that you've complied satisfactorally with giving them access. I find that left brain analytical types tend to only apply left brain methodology and thinking in their designs. Throwing right brain methodology into the equation could add just enough incongruence to the process that it might serve to confuse the shit out of the cryptographer trying to make sense of it through left brain analysis. In fact it might serve to heighten the incongruence factor when the crypt-breaker is a two-left-brain type.. present company who relate to that chosen lifestyle, please take no offense BTW ! :-) So, anyway, my humble apologys to those who may think my flights of fancy are malicious fluff, or an annoyingly gross abuse of S/N here. My mind actually does work this way, I don't know what I can't do. LUX ./. owen By the way, Monday - Oct 11th is National Coming Out of the Closet Day. write an encryption scheme that encodes man pages as homo-erotic sonnets, and send the output to your congress-critter(TM), sign them with Sam Nunns name for bonus points.