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 Post subject: Steganography
PostPosted: Sun Jan 29, 2017 11:14 am 
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I am not sure if anyone here would be interested, but during the bad weather I entertained myself indoors by writing a program that hides text messages in jpg image files. The general technique is called steganography, but my program uses none of the techniques described in the article.

I am not sure how 'useful' such a program is.... it was more of a mental exercise. Some might find it entertaining, though, so I thought I would share.

Anyway, the program is free to all - let me know what you think.

Phill

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 Post subject: Re: Steganography
PostPosted: Thu Apr 27, 2017 4:11 pm 
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Yes, but can you hide a photo in text?

All in all cool stuff. I'll have to use something like this if I ever put photos on the internet with my information hidden in it so that if it is lifted it can be verified that it was my work.
What happens if someone reduces image size to a thumbnail, is the hidden message left intact? What if it is cropped? How robust to modifications is it?

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 Post subject: Re: Steganography
PostPosted: Fri Apr 28, 2017 1:22 am 
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I.D.10-t wrote:
Yes, but can you hide a photo in text?

I am not sure what you are asking. The amount of data required for an image is much, much larger than the amount of data required for a piece of text. And the accuracy of the data required for the image is much lower than the accuracy required for text. So the small amount of accurate data needed for a line of text can be hidden inside the inaccuracies in the large amount of data for an image. I cannot see h ow it would be practical to hide an image in text unless the image were very small and the text was very large.

I.D.10-t wrote:
What happens if someone reduces image size to a thumbnail, is the hidden message left intact? What if it is cropped? How robust to modifications is it?

Not at all robust - that was not its goal. Any modification of the image requires a re-encoding stage, and that will lose the hidden data.

There are other forms of steganography that hide a low quality image inside a 'high quality' image. I would image that these are more robust against modification but I cannot see that being useful as a digital watermark.

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 Post subject: Re: Steganography
PostPosted: Wed Jun 21, 2017 4:42 pm 
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DrPhill wrote:
I.D.10-t wrote:
Yes, but can you hide a photo in text?

I am not sure what you are asking. The amount of data required for an image is much, much larger than the amount of data required for a piece of text. And the accuracy of the data required for the image is much lower than the accuracy required for text. So the small amount of accurate data needed for a line of text can be hidden inside the inaccuracies in the large amount of data for an image. I cannot see h ow it would be practical to hide an image in text unless the image were very small and the text was very large.

At first I was joking, but there are ways of hiding file size in unused storage space and making file sizes look appropriate. Not a programmer, but it seems like a fun challenge.
.
DrPhill wrote:
I.D.10-t wrote:
What happens if someone reduces image size to a thumbnail, is the hidden message left intact? What if it is cropped? How robust to modifications is it?

Not at all robust - that was not its goal. Any modification of the image requires a re-encoding stage, and that will lose the hidden data.

There are other forms of steganography that hide a low quality image inside a 'high quality' image. I would image that these are more robust against modification but I cannot see that being useful as a digital watermark.
How could you make it more robust and include audio?

I do not code this kind of thing, but I like to nest things. Video>audio>text. I do like to ask things of people that can tell me what is impossible and those that say let me get back to you.

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 Post subject: Re: Steganography
PostPosted: Sat Jul 01, 2017 11:09 am 
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I think Id-10-t is speaking of the Microdot - famous in 1950s spy movies and probably nowhere else.

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