Concealer

Concealer is a good small application that will help you hide your secret files inside binary files. You only have to add the file you want to hide and afterwards select the file inside of which you want to hide it, which will be the decoy.

The decoy can be any type of file, but it's better if it is a binary file (images, applications, or pdf), since those text files already have a bunch of strange content.

After, you just have to assign a password (although in the demo version, one will be created automatically) that will help you recover your hidden file in the future.

Finally, you will be given a file that looks just like the one that you've chosen as the decoy, but which actually contains your secret inside of it.

If you want to hide your secrets, Concealer is an application that's very effective since it allows you to convert any ordinary file on your computer into the holder of your secret.