3 ms·

For extra security, it's good to provide the option of encrypting the message before hiding it in the image. Doesn't encryption make it easier to detect hidden

by dchest 14y ago

For extra security, it's good to provide the option of encrypting the message before hiding it in the image. Doesn't encryption make it easier to detect hidden messages, because it generates a uniform pseudorandom output, something that an image without the hidden message doesn't have?

gw 14y ago
I haven't done much steganalysis so don't know what difference it will make for an attacker searching over large numbers of images, but it's at least useful if you're more worried of attackers who already suspect there is a hidden message.
harshpotatoes 14y ago
All images have some amount of random noise in them due to the thermal fluctuations of the sensor. With some clever techniques, I wonder if it could be possible to hide the pseudorandom encrypted message in the image to make it appear slightly noisier? Or maybe hide the message in images with already low SNR?
thalur 14y ago
I would have guessed the opposite - I would expect the least significant bits to have a random distribution (if the image is a photo from a camera, that is) so if the least significant bits of the image have a non random distribution that might be a hint that there is something hidden there. Of course, all of this is moot if the image is lossily compressed.
peterwwillis 14y ago
This paper recommends embedding AES using a thresholding algorithm: http://www.scribd.com/doc/62034623/A-Multi-Layered-Secure-Robust-and-High-Capacity-Image-Steganographic-Algorithm http://www.scribd.com/doc/62034623/A-Multi-Layered-Secure-Ro... This paper is really good at explaining image steganography from a beginner's standpoint: https://docs.google.com/viewer?a=v&q=cache:kWVnLQVjyR0J:martinolivier.com/open/stegoverview.pdf+&hl=en&gl=us&pid=bl&srcid=ADGEEShqeA3VSpam5rS7capPIrbzk22kTtJBMEBWVtXQ-jSrv6GAT4IX1L0KIzbA_PvhL8_IvJhyLk8LWn3IMK-VZO5Rb-8yMPYEIZa71yZ7HaXsPTdXF69vF6mUS5aE6lJA_YXFYxQO&sig=AHIEtbQg9VAMBeSntkcN-_WClletsaZMpQ&pli=1 https://docs.google.com/viewer?a=v&q=cache:kWVnLQVjyR0J:... In my opinion, the whole point of embedding a "secret" message in an object is defeated if there's the possibility that the "secret" may be revealed. The math involved in cryptography is much harder to defeat than the art of detecting a structured message layered into an object, so I prefer to just pass a plain-old encrypted message. But if you want to prevent someone even thinking you're passing an encrypted message, embedding that encrypted message in an image or audio can be beneficial. And risking someone finding out the actual secret just because you thought they might be able to tell you're sending one is not worth it.
- dchest 14y ago
  Thank you for the links! Indeed, I was thinking about applying some form of encryption that is harder to distinguish from image data than just AES in standard modes.

by dchest 14y ago

gw 14y ago

I haven't done much steganalysis so don't know what difference it will make for an attacker searching over large numbers of images, but it's at least useful if you're more worried of attackers who already suspect there is a hidden message.

harshpotatoes 14y ago

All images have some amount of random noise in them due to the thermal fluctuations of the sensor. With some clever techniques, I wonder if it could be possible to hide the pseudorandom encrypted message in the image to make it appear slightly noisier? Or maybe hide the message in images with already low SNR?

thalur 14y ago

I would have guessed the opposite - I would expect the least significant bits to have a random distribution (if the image is a photo from a camera, that is) so if the least significant bits of the image have a non random distribution that might be a hint that there is something hidden there. Of course, all of this is moot if the image is lossily compressed.

peterwwillis 14y ago

This paper recommends embedding AES using a thresholding algorithm: http://www.scribd.com/doc/62034623/A-Multi-Layered-Secure-Robust-and-High-Capacity-Image-Steganographic-Algorithm http://www.scribd.com/doc/62034623/A-Multi-Layered-Secure-Ro... This paper is really good at explaining image steganography from a beginner's standpoint: https://docs.google.com/viewer?a=v&q=cache:kWVnLQVjyR0J:martinolivier.com/open/stegoverview.pdf+&hl=en&gl=us&pid=bl&srcid=ADGEEShqeA3VSpam5rS7capPIrbzk22kTtJBMEBWVtXQ-jSrv6GAT4IX1L0KIzbA_PvhL8_IvJhyLk8LWn3IMK-VZO5Rb-8yMPYEIZa71yZ7HaXsPTdXF69vF6mUS5aE6lJA_YXFYxQO&sig=AHIEtbQg9VAMBeSntkcN-_WClletsaZMpQ&pli=1 https://docs.google.com/viewer?a=v&q=cache:kWVnLQVjyR0J:... In my opinion, the whole point of embedding a "secret" message in an object is defeated if there's the possibility that the "secret" may be revealed. The math involved in cryptography is much harder to defeat than the art of detecting a structured message layered into an object, so I prefer to just pass a plain-old encrypted message. But if you want to prevent someone even thinking you're passing an encrypted message, embedding that encrypted message in an image or audio can be beneficial. And risking someone finding out the actual secret just because you thought they might be able to tell you're sending one is not worth it.

dchest 14y ago
Thank you for the links! Indeed, I was thinking about applying some form of encryption that is harder to distinguish from image data than just AES in standard modes.