Secrets Hidden in Images (Steganography) - Computerphile

Secret texts buried in a picture of your dog? Image Analyst Dr. Mike Pound explains the art of steganography in digital images.

This video was filmed and edited by Sean Riley.

[orazioballal]

If you download this video you'll discover that every single frame contains "I'm the editor working hours in the basement, please send help"

[JustOneAsbesto]

Steganosaurus is my favourite dinosaur.

[garethdean]

Truly this is a remarkable area of study. Why just the other day I was looking at what appeared at first to be a picture of a herd of braying donkeys. It was only with careful scrutiny of the image I realized that O was actually staring at a picture of parliament.

[samnub]

From now on, I'm going to watermark all my image work with the tragedy of darth plaguis the wise

[TommiHimberg]

A very interesting video on how e.g. the entire works of Shakespeare can be hidden in one digital photo. Kudos to Dr Pound for yet another extremely clear and understandable explanation of a complex topic!

[lollelolle]

I could listen to this guy for ages and never get bored. The topics he presents are so fascinating and he presents them very well. Nice work

[CliveReyes]

Every time Dr. Pound makes a video he goes "oh I've written a program for this..." then they never show us the code! It would be fantastic if you guys could share Dr. Pound's work for learning purposes.

[richard]

I must have watched a million Tech videos and read three times as many online articles before I found this guy here on computerphile and I have come to realize without question that this man is dangerous. Very few people possess this level of knowledge and the videos are by far the best on the internet. Keep up the good work!👍👍

[jody]

My professor didn't give us any detailed explanation on this topic but you gave a wonderful one. Thank you!

[Mysteryem]

A fairly good example of steganography that you may have come across without realising was the video game Spore. In it, you could drag the images of into the game's editor and it would then read the hidden data describing that creation from within the image and load it into the editor.

[bambel]

I am very glad you didn’t just show us the image and have us take your word for it that the images were different!

[shanedk]

I played around with this a bit in the late '80s. I wrote a program that would take a TGA file and put the message in the two least significant bits of each channel, just as he describes in the video. I found that I could tell the point at which the message stops, because the image just gets a bit less noisy and more clean. This could be an indication to someone else that you were hiding a message, if they were familiar with the process.

My solution was to generate random numbers and do the rest of the pixel data randomly. If your message is encrypted (which it should be; steganography is no substitute for sound encryption), then it should be indistinguishable from randomness anyway, so this should successfully hide the fact that you've hidden a message to begin with.

Of course, this isn't going to work with lossy algorithms like JPG. Today, just use PNG.

[Delicious]

There was a story about how a big company like Tesla found out who leaked their documents.

Every employee that got those documents received his version. And the only difference was a double space-character somewhere in the doc.
So after it got leaked, they only had to look where in that doc the double space was, and therefore found the whistleblower

[skrdman]

This is brilliant. You can effectively store 1/4 as many bits of data in an image as the image has while only modifying the original image by less than 1/64th.

[thechrisgrice]

Okay, the message at the start had me laughing.

[dustinbreakey]

you telling me that there are secret messages in the rarest of pepes?

[TheCreatorJames]

Every time I research and implement something, Computerphile releases a video within a week on the same topic. GG Computerphile.

[robertcrier]

I love your videos, i bought like 8 books on security including the CISSP exam study, and I’m learning a ton from watching your videos. I even studied cryptography because i love computers, i used to love science, now its CS.

[lukasdon]

Instead of trying to detect JSTEG, wouldn't it be possible to destroy the message by slightly altering the image? For instance, you could add a very slight blur, NR or USM which doesn't alter the image that much, but completely ruins any hidden message. Or add a small and complex distortion pattern, etc.

In other words: if I upload a JSTEG image to facebook/whatsapp, and then the image gets recompressed/resized or noise reduction is applied, then it would be impossible for the receiving party to recover the message hidden inside.

[staticbuilds]

I am thankful I know game design as knowing how PNG images are used to optimize textures helped me understand this greatly.