Hide a message in an image - Robbers

Question

Choose a challenge from the Cops thread, determine the third hidden message, and describe how the system works.

Keep in mind limitations and possibilities available to Cops:

• You are not expected to guess any cryptographic secrets or additional information required to extract the hidden messages, as they should have already been included in their post.
• The hidden message will be in English
• The hidden message may be encoded as plain text, a text bitmap rendering, audio clip, or ascii art font. This encoding will be consistent across all hidden messages.
• No further processing will be required after obtaining the hidden message.
• Data is allowed to be hidden in metadata, but at least one bit of one pixel must have been used for something.

Score 1 point per cracked system.

Answer 1

CreaZyp154's

I don't know the first thing about image encodings, but it looks like in each of the three images every pixel is an index into a palette containing two identical colors. Messages are encoded as transposed images in the palette indices.

Thus, the third image says STEGANOGRAPHY:

Answer 2

emanresu A's

Image 1, which encodes HI, can be decoded by turning it into a 32×32 square:

Same with Image 2, which encodes BYE:

And, with Image 3:

The words OI You!

Since all the images are 1024×1, you just need to split it into segments 32 pixels wide, and stack them on top of one another.

Here's a tool I wrote to do this: https://gist.github.com/Radvylf/b5d1bc5f39903400b243abf2041feefe