SecretLayer is a Windows program to encrypt and hide messages inside a photograph (jpg, png, gif, bmp), this is known as steganography. The program tweaks photo pixels and embeds tiny pieces of extra information in them without changing how the pictures look to the human eye.
The tests I performed made the carrier photos indistinguishable from the original files except for being slightly bigger in size, a few Kilobytes more, depending on the size of the secret message. You will be told by SecretLayer how much data you can hide inside each photograph, a progression bar indicates how many bytes you can hide as you type. Or if you add an attachment, you are told what the maxium size can be. This is the kind of program that computer beginners can use, it comes with a video tutorial and a wizard allowing you to learn how all works in under 5 minutes.
With SecretLayer you can send covert messages sidestepping email by uploading images with hidden data to a personal photo album or website, the receiver will only have to visit the website and save the photo. With one small caveat, the person decrypting the message has to know what encryption algorithm and key length were used, you will have to transmit this one way or another, just once if you don’t change the arrangement.
This is a very easy to use program with a wizard guiding novices step by step and an advanced function that lets you choose encryption algorithm of in between AES, Blowfish, IDEA, CAST, DES and RC5. Secret Layer displays information about the security level of each encryption method and keybit length, there are also security tips in the password window so that you do not enter anything that could be guessed or easily broken. A small improvement I feel the developer could make is adding a password strength meter.
After encrypting a file you can choose where to save the image, ticking a box tells SecretLayer that you would like to shred the original picture, something I would advice you to do. Wiping the original picture will make it nearly impossible for somebody to find out if the resulting photograph contains hidden data inside or not. To discover steganography in a digital photo the original is needed to make a comparison.
SecretLayer can also wipe the data you are hiding when you are done. The integrated file wiping utility is much appreciated, eliminating secret messages in plain text considerably increases your security.
I always liked steganography because it is very hard to detect and if you add to that encryption, mass surveillance loses capabilities, the powers that be can’t scan every single picture on the Internet looking for hidden data. Of course I would have preferred an open source tool, other than that, I liked SecretLayer and I am convinced that if PGP was as easy to use there would be many more users.
To your attention, the free version of Secret Layer, called Light, does not encrypt data, it only hides it, if you want encryption and be able to split and hide data in between multiple photos, which allows for bigger files to be hidden, you will have to buy this program and, steganography without encryption might fool your room mate but not somebody who has the right tools to extract data. For a, not so easy to use free alternative check out OpenPuff Steganography.
As it is usual in these programs, the person you communicate with will need to have it installed too.