Re: Steganography -- Tell-tale signs?

Hi there!

I'd appreciate some help from you experts in 
steganography.

1) If I hide some PGP encrypted data in a
gif, jpg or wav file will there be any tell tale 
signs to the naked eye of an expert? If yes,
what are they?

2) Would it better to hide the data in 
a jpg with black and white image rather
than a color one?

3) Are there any tools at the moment 
to expose (not crack) the hidden encrypted 
data? If none. are there tools in development?

If this appears twice please accept my apologies.
I didn't see the first posting and so I assumed it 
was lost in transit. Please email replies to me 
directly if this is off-topic. Thank you.

Makofi

> 
> Hi there!
> 
> I'd appreciate some help from you experts in 
> steganography.
> 
> 1) If I hide some PGP encrypted data in a
> gif, jpg or wav file will there be any tell tale 
> signs to the naked eye of an expert? If yes,
> what are they?

If you stego too many bits in a figure, it may become apparent.

> 
> 2) Would it better to hide the data in 
> a jpg with black and white image rather
> than a color one?
> 

24 bit color has more data, therefore its easier to hide random data.

> 3) Are there any tools at the moment 
> to expose (not crack) the hidden encrypted 
> data? If none. are there tools in development?

Not really.  If you make sure there are no predictable headers, and use a
good encryption algorithm, it is almost impossible to tell the presence of
a hidden file unless you compare a file untouched with the one with data
in it.

> 
> If this appears twice please accept my apologies.
> I didn't see the first posting and so I assumed it 
> was lost in transit. Please email replies to me 
> directly if this is off-topic. Thank you.
> 
> Makofi
>

> > 1) If I hide some PGP encrypted data in a
> > gif, jpg or wav file will there be any tell tale 
> > signs to the naked eye of an expert? If yes,
> > what are they?
> 
> If you stego too many bits in a figure, it may become apparent.

The new version of Photoshop coming out this fall includes the ability to
embed "digital watermarking":

(from http://www.news.com/News/Item/0,4,3188,00.html: 

                Digital watermarking
                adds copyright information to
                a photograph that doesn't alter the photo's
                appearance. The watermark is detectable even
                after the photo is edited or printed and rescanned. 

Question: Will stegonagrphying (?) the picture with noise mar the
watermark? Will a digital signature *and* something embedded into the
graphic through steganography seriosly affect a 24-bit image?

Furthermore: What about browsers? Could cookies or binary info be embedded
into images on the fly so that a java applet could preserve information or
states between pages, of different sites?

Just thoughts..

Jason Vagner