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steganographic encryption

Hide encryption in plain sight
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There is a lot of talk about the legality of "Common folk" having access to software encryption technology. I'm sure there are plenty of people in political positions who do not believe that ordinary citizens have the right to private communication.

While it is not currently the case, it is possible that one day, even sending an encrypted message could be illegal. Even if it were not, the argument could be made that if there are agencies spying on people (and this is not a place to argue as to whether or not this happens), receiving messages that are obviously encrypted could result in more intense and thorough spying on that individual.

Steganography is the practice of hiding sensitive things in plain sight, but in such a way that only the hider and the recipient are able to use the item (most often this is used in computer encryption).

In modern computing, it is estimated that this often takes place in images sent between two parties wishing to share a secret. The problem with hiding this information in images is twofold -

One, the method of encrypting and decrypting must be shared, as there is no common protocol for this. This introduces the possibility of interception of the means of decryption.

Problem the second: Given its nature, steganography in images either has a limited storage capacity, or is easy to see with distortions in the image.

Bring in the idea: Using standard off the shelf encryption (such as pgpi), generate a message with your recipient's public encryption key. Run your encrypted message through a dictionary similar to that for the "one time password library" (like S/key - see link), with an exception - the dictionary is much larger, has many more words per unit.

I should elaborate on this point: I mention S/key because it takes a small but complicated string and turns it into whole words. That is the only relation to OTP. The method of re-encryption I outline here otherwise has nothing to do with one time passwords.

Using the fact that your new dictionary is much larger, form basic sentences and paragraphs that "almost" tell a story - that is, they would pass microsoft word's grammar checker.

When the recipient gets the message, s/he will run it through the library backwards, arriving at the original encrypted message, which will then be unencrypted as standard.

The library will be set up with no checksums or data verification techniques, such that any string of words, whether it was generated with the library or not - can be "unconverted". This will prevent spies from simply checking to see if the message has been made up with the library or not.

The message received would be much much larger than the one it boils down to when unencrypted, but it would appear as just a message to any spying agencies trained to pick out encrypted messages in the ether. Moreover, if you were being personally scrutinized, the message would look like most of the spam that is sent these days, the messages of garbage sentences that are used to throw off bayesian filters.

The obvious trick is in sending the message then, and not receiving it - It is one thing to receive a message that looks like spam than to send one - once again, triggering our covert agencies' attention. To solve this problem, one might implement one or more of the following ideas: 1) Cherry pick the result of the library conversion to represent an intelligible message 2) utilize systems such as anonymous remailers, TOR, and public network facilities (schools, someone's unlocked wifi, cyber cafes) to hide the origin.

ericscottf, Feb 28 2008

S/key http://en.wikipedia.org/wiki/S/KEY
One time password info [ericscottf, Feb 28 2008]

Linguistic Steganography http://semantilog.ucam.org/biblingsteg/
The state of the art around 2006 [jutta, Feb 29 2008]


       Well, that's the problem, isn't it? You have a shared secret between you and the recipient. This method involves public software and no shared secrets.
ericscottf, Feb 28 2008

       1) Just because your s/key scheme produces a series of words that are valid in Word, doesn't mean they'll form a story. That's a whole other animal.
2) If the dictionary you're using is public, what stops me from using it to get back to the public-key encrypted message?
3) It won't look like spam unless your message is *very* short, and then only if there are one or more URLs floating around in it.

       What's wrong with PKI by itself?
phoenix, Feb 28 2008

       The general field of cyphertext masquerading as human language text is called "linguistic steganography". It's far too low-bandwidth in practice, but I like your idea of making the input public key cyphertext, for any form of steganography. I don't know whether people already do that or not.   

       Spam generators and steganography programs have quite a bit in common, and address similar problems - your main worry would be how to not get spam-filtered by your recipients!
jutta, Feb 29 2008

       Phoenix: 1) Part of what the software will do is to assemble the proper words to form basic sentences. This is why the dictionary has many words per unit. It can choose from a noun, verb, adjective, for a single spot. The story doesn't have to be great, remember, we're trying to make our messages blend in with the background, not win a pulitzer. 2)Yes, the dictionary will be public. If encryption required secrets in the software, it would be useless. Like i wrote: "The library will be set up with no checksums or data verification techniques".... This means you could use the software to go from the doubly-encrypted message to the raw PGP on any string of words, whether or not it was actually encrypted with this. That means you won't be able to tell if this message is encrypted or not - you'd get either an unencryptable message (if you have the proper private key) or a string of garbage that *looked* like an encrypted message. If you don't have the key, it all looks the same.   

       Spammers (though i have dealt with my spam problem and i haven't gotten any in awhile) send large blocks of random text and words in an effort to ruin peoples' bayesian filters. This would look like that, only with better sentence structure (though I've seen some spam where it was just sections of novels)   

       Una: It is not a secret shared with a small group - the library would be public. I don't do anything illegal, but I don't believe that anyone has the right to spy on my conversations, or even know that i'm having conversations i don't want spied on. the "nothing to hide" argument is a fallacy at best and dangerous at worst. I could go into detail about how when peoples are spied upon casually and with no basis, you are in more danger, but as i mentioned in the beginning of my entry, this is not the place for that. Even if it were, i'm not the type to argue about such things with people.
ericscottf, Feb 29 2008

       Here's another idea for ultra-secure email which cannot be intercepted by any known computer snooping system: Once you press the 'Send' button, the email client doesn't send the email, but looks up the snail-mail address of the recipient in your address book, and sends the email and address to your printer to print the email and an envelope. You stick a stamp on (postage calculated by your email program), nip outside and post it.
hippo, Feb 29 2008

       "Part of what the software will do is to assemble the proper words to form basic sentences...Spammers (though i have dealt with my spam problem and i haven't gotten any in awhile) send large blocks of random text and words in an effort to ruin peoples' bayesian filters. This would look like that, only with better sentence structure (though I've seen some spam where it was just sections of novels)"
I understand you're trying to obfuscate the fact that the message is encrypted. I'm just not sure that's possible (today) and, if it were, that you'd be successful hiding from me if I were actively parsing your sent mail.

       If we're working on the presumption that the underlying PKI is unbreakable, you're safe sending the unobfuscated (but encrypted) message. On the other hand, if you presume the PKI can be/has been compromised, it would be trivial to de-obfuscate your message anyway.   

       I say go for it if it makes you feel better, but it strikes me as if you're painting your safe to look like a television.
phoenix, Feb 29 2008

       Well, that's the entire idea, isn't it? Avoid the issue of untrustworthy agencies paying more attention to you because you are sending encrypted messages by removing their ability to easily tell that you are sending encrypted messages.   

       You (representing some unpleasant agent) are not *actively* parsing my mail, you are monitoring your giant screen that says "echelon" at the top. I look no different than the 6 trillion other people in the world. This system makes my emails look like all the rest. You have no reason to take any closer of a look at my life than anyone else's. The privacy of my life has just increased.   

       This idea was never to increase the strength of public key encryption, as that is completely unnecessary. public key encryption, in my (and most other sane peoples') opinion, is relatively secure.   

       Isn't that why so many safes are hidden behind pictures?
ericscottf, Feb 29 2008

       That just makes you *more* suspicious in my book. Anyway, we've already keyed in on you through this post and will be keeping an eye on you from now on.
phoenix, Feb 29 2008

       Certainly it makes me more suspicious, but there's no way to tell (if my idea works properly).   

       That aside, i haven't had a working public key for years. Just because i don't have a need for it doesn't mean i don't find the ideas fascinating...
ericscottf, Feb 29 2008

       Wondering if governments could get one half of a paranoid schizophrenic to spy on the other personliaty/ies?
DrCurry, Feb 29 2008

       Where do the stegosauruses come in?
bnip, Mar 02 2008

       Steganography is the hiding of the existance of the message itself. i.e. The concealment that there was a message in the first place. It is the inverse of spam, irt: Spam: I am AND should be here, Steg: I am not AND did not go there.   

       This message can be plaintext, and in early instances usually was, or ciphertext. In the case of ciphertext; over the result a covertext is applied to produce a stegotext. The fact that all the components have been named in cryptological jargon is a sure sign that this is baked, possibly widely known to exist. However, I am not aware of any commercial products.   

       1. Regardless of the lack for a shared secret key you are still not addressing the fact that there is knowledge that the two parties have communicated. The legislation you are so worried about would include a phrase similar to: "Where the parties could reasonably have been expected, or proved, to have communicated, those communications being clandestine, presumed or otherwise, etc..."   

       2. Diffie-Hellman-Merkle key exchange protocols like PGP, PK, ECC, discrete logarithm leave a recognisable signature in the ciphertext, due to their algorithms. It stems from the fact that you exchange a set length key, then hash, block cipher, etc. This could be disguishable (yuk) by parsing the text/image and looking for that signature. It is quite often that cryptanalysts will know your encryption method from the "fingerprint" of the ciphertext. This does, in no way, aid in the brute force cryptanalysis itself. Unless of course you have access to the certificates or private key. Your method does nothing to obfuscate this signature.   

       3. The most effective known application of steganography, in its purest form (not these paedophile rings, serving only to hide content not communication), is the multi-directional transmission of a constant stream of noise. Noise is good because it is completely random, much like the OTP encrypted data being transmitted. Multi-directional is good (as opposed to sending your best friend a constant stream of noise) as it has no address-ability (yuk). The success of this method relies on the fact that you can only use OTP. The method of "switching on" the Pad during this noise is one of the miracles of human innovation.   

       4. Google mimic functions.   

       5. In the same way that PKI suffers a "man-in-the-middle" attack, your idea would benefit from a "man-in-the-middle" defense. Daily posting and subscription to an arbitrary RSS feed, social network, etc, could hide the fact that you are directly communicating to an individual as opposed to the normal group. (assuming that we are only intend avoiding the possibility of investigation, as the stegotext will not stand under scrutiny).
4whom, Mar 02 2008

       On a lighter, and not completely different, note. The standard joke, here, for general encryption is:   

       The phrase: "I must confess my undying urge to love you." passed through several iterations of Google translator or Babelfish (in several, varying, languages), should in the end return your true feelings.
4whom, Mar 02 2008


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