Metadata is so last decade. ;-) Ever heard of steganography? It's a technique where you can hide, for instance, a textfile inside an image file, all neatly encrypted and password protected. There are several tools outthere, I use Photocrypt. According to the description of Photocrypt it works as follows:

It implements a modified LSB (least significant bit) substitution algorithm with password protection. Every bit of secret data is stored in the less significant bits (not always least) of the image pixel color values. This makes the stego-image practically identical to the original image. The algorithm depends on the key so it is unfeasible to extract data without the key.

The algorithm used in this program can be explained briefly as:

The 1st row of image is used to store the SHA1 digest of the password. The bits used to hide the data depends on the key itself. This is required to add password-verification feature.

The secret data starts from the beginning of the 2nd row. The bits used to hide the data depends on the key itself. The \0 character is appended at last to mark the end of text.

So, there you go! And try to think about the things you see online or the files people send you... is there something hidden inside it?
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