14.7.1. (Another one of the topics that gets a lot of posts)
14.7.2. Hiding messages in other messages
- "Kevin Brown makes some interesting points about
steganography and steganalysis. The issue of recognizing
whether a message has or mighthave a hidden message has two
sides. One is for the desired recipient to be clued that
he should try desteganizing and decrypting the message, and
the other is for a possible attacker to discover illegal
uses of cryptography.
"Steganography should be used with a "stealthy"
cryptosystem (secret key or public key), one in which the
cyphertext is indistinguishable from a random bit string.
You would not want it to have any headers which could be
used to confirm that a desteganized message was other than
random noise." [Hal Finney, 1993-05-25]
14.7.3. Peter Wayner's "Mimic"
- "They encode a secret message inside a harmless looking
ASCII text file. This is one of the very few times
the UNIX tools "lex" and "yacc" have been used in
cryptography, as far as I know. Peter Wayner, "Mimic
Functions", CRYPTOLOGIA Volume 16, Number 3, pp. 193-214,
July 1992.[Michael Johnson, sci.crypt, 1994-09-05]
14.7.4. I described it in 1988 or 89 and many times since
- Several years ago I posted to sci.crypt my "novel" idea for
packing bits into the essentially inaudible "least
significant bits" (LSBs) of digital recordings, such as
DATs and CDs. Ditto for the LSBs in an 8-bit image or 24-
bit color image. I've since seen this idea reinvented
_several_ times on sci.crypt and elsewhere...and I'm
willing to bet I wasn't the first, either (so I don't claim
any credit).
A 2-hour DAT contains about 10 Gbits (2 hours x 3600 sec/hr
x 2 channels x 16 bits/sample x 44K samples/sec), or about
1.2 Gbytes. A CD contains about half this, i.e., about 700
Mbytes. The LSB of a DAT is 1/16th of the 1.2 Gbytes, or 80
Mbytes. This is a _lot_ of storage!
A home-recorded DAT--and I use a Sony D-3 DAT Walkman to
make tapes--has so much noise down at the LSB level--noise
from the A/D and D/A converters, noise from the microphones
(if any), etc.--that the bits are essentially random at
this level. (This is a subtle, but important, point: a
factory recorded DAT or CD will have predetermined bits at
all levels, i.e., the authorities could in principle spot
any modifications. But home-recorded, or dubbed, DATs will
of course not be subject to this kind of analysis.) Some
care might be taken to ensure that the statistical
properties of the signal bits resemble what would be
expected with "noise" bits, but this will be a minor
hurdle.
Adobe Photoshop can be used to easily place message bits in
the "noise" that dominates things down at the LSB level.
The resulting GIF can then be posted to UseNet or e-mailed.
Ditto for sound samples, using the ideas I just described
(but typically requiring sound sampling boards, etc.). I've
done some experiments along these lines.
This doesn't mean our problems are solved, of course.
Exchanging tapes is cumbersome and vulnerable to stings.
But it does help to point out the utter futility of trying
to stop the flow of bits.
14.7.5. Stego, other versions
- Romana Machado's Macintosh stego program is located in the
compression files, /cmp, in the sumex-aim@stanford.edu info-
mac archives.
- "Stego is a tool that enables you to embed data in, and
retrieve data from, Macintosh PICT format files, without
changing the appearance of the PICT file. Though its
effect is visually undetectable, do not expect
cryptographic security from Stego. Be aware that anyone
with a copy of Stego can retrieve your data from your PICT
file. Stego can be used as an "envelope" to hide a
_previously encrypted_ data file in a PICT file, making it
much less likely to be detected." [Romana Machado, 1993-11-
23]
14.7.6. WNSTORM, Arsen Ray Arachelian
14.7.7. talk about it being used to "watermark" images
14.7.8. Crypto and steganography used to plant false and misleading
nuclear information
- "Under a sub-sub-sub-contract I once worked on some phony
CAD drawings for the nuclear weapons production process,
plotting false info that still appears in popular books,
some of which has been posted here....The docs were then
encrypted and stegonagraphied for authenticity. We were
told that they were turned loose on the market for this
product in other countries." [John Young, 1994-08-25]
- Well...
14.7.9. Postscript steganography
- where info is embedded in spacings, font characteristics
(angles, arcs)
- ftp://research.att.com/dist/brassil/infocom94.ps
- the essential point: just another haystack to hide a needle
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