How do you embed info in pictures?

Coding a few pixels or making the equiv of a microdot using a few pixels from a hi-res image.

Here’s the idea although I haven’t ever actually tried it.

Using the jpeg encoding standard as an example, the image file consists of a certain number of bits that represent a pixel. If you have a 24-bit resolution file, every 24 bits represents a pixel. In general the low order bit, the last of the 24, if changed will have little impact on the overall image.

Now take the data you want to embed as a bit stream and make the low order bit of every pixel representation match the corresponding bit of your data file. You have not changed how the image looks much, and you have embedded data that can later be extracted from the image.

Note that this is a very simplified answer. This can get complicated when you start to look at the particulars of the image encoding and if you start to include error correction in your hidden data.

I’m not exactly sure what you mean by embedding the passwords. But you can hide an archive (with whatever documents you’d like) within an image.
You’ll want to have your image file (input.jpg) and archive file (input.rar), and have them, say, in C:\Folder
Open up command prompt and say cd C:\folder to point to the folder, and then do copy /b input.jpg + input.rar output.jpg.
Anyone browsing through your stuff will just think it’s a standard image. They can open it up, and it’ll open just like any image would. But you could also open it up with an archive program and it’ll show everything from input.rar inside.
I threw a quick video on youtube. But it’s still processing at the moment. And ooh, a recommended video is a Janelle Monae song? I can deal with that.

The practice of hiding information in pictures is a kind of steganography.

There are several programs available to help you with this. More information available here.

There is a straightforward way to do this: IPTC information. You can get a free application called IrfanView that will let you enter IPTC info as well as view any such information a picture contains.

http://bppdocs.camner.net/html/iptc_info.htm
http://www.irfanview.com

This is substantially different from steganography, which is a method of embedding hidden information into pictures (or other kinds of binary files) by manipulating a few bits of the color information.