From: Eric Fogleman <Eric.Fogleman@analog.com>
Date: Thu, 11 Mar 93 10:10:59 PST
To: uri@watson.ibm.com
Subject: Re: Hiding Encrypted Messages
Message-ID: <9303111807.AA16545@ack.adstest.analog.com>
MIME-Version: 1.0
Content-Type: text/plain


> > 2. Then take an encrypted PGP file and dispurse it bit-by-bit into the
> > LSB (least-significant-bit) of each sample.  This wouldn't distort the
> > sound sample to any extent noticable by the human ear.  Thus each byte
> > of PGP file would be dispursed into 8 bytes of sound file.  Thus if
> > you wanted to send a 20k PGP file, you would have to put it into a
> > 160k music file.
> > If you're ever forced to explain what that file contains (unlikely, since
> > you can always take the Fifth Ammendment) you can just play it on your
> > computer and have the NSA/SS/FBI/Whatever listen to James Brown go
> > "Hyeeeah... I feel good!"
> 
> a) This method has essentially the same complexity, as one-time pad,
>    but without it's strength.
> 

Insert pgp-encrypted (not plaintext) into the sound file...  It's then
no weaker that pgp.

> b) If it's played and recognized - one can trace your source (a CD, a
>    tape of radio broadcast, whatever) and do a comparison. Then the
>    file containing of all the LSBs is cryptanalyzed...

Use a "windows sound system" board and record yourself talking --
No "reference source"... The codec on that board has better than 
two bits of noise per 16 bit word through the ADC channel...

Nice idea, thug!

===================================================================
Eric Fogleman                              eric.fogleman@analog.com
Analog Devices Semiconductor               Voice: (617) 937-2275
804 Woburn Street                          Fax: (617) 937-2024
Wilmington, MA  01887-3462                 
===================================================================