Most of us used lemon juice as invisible ink to write letters to our friends while we were kids. Seeing words emerge — almost magically — as we put a white sheet of paper up in front of a candle flame was an indescribable thrill. What you could not have realised at the time is that this experiment shows both oxidation and steganography!
We’ll look at some common steganography tools and how they can help with steganalysis in this article. But first, let’s take a look at how steganography came to be, as well as the distinctions between steganography and cryptography.
Security Through Obscurity: What Is Steganography?
Steganography is the art of concealing data (in some medium — text, photograph, etc.) inside another entity in plain sight. This method helps you to submit data undetected and without arousing suspicion.
While the first known use of steganography dates back to ancient Greece, it was Johannes Trithemius in 1499 who gave it a name with his book Steganographia. Digital steganography has grown in popularity over time as a result of technical advancements. Here are few examples of more recent steganography:
- microdots being heavily used during the world wars,
- prisoners blinking in Morse code, and
- Cicada 3301 internet puzzles.
Modern spy rings also used steganography to leak secret information back to intelligence, such as the Illegals Program, a network of spies that used steganography to leak classified information back to intelligence.
So, what is steganography and how does it work? Consider the following scenario:
Let’s say Erin needs to give Todd a hidden letter that no one else knows about. He hides the hidden message inside a carrier object, such as an audio clip or an image file, using a steganographic technique. Erin can now submit a new stego entity to Todd without arousing suspicion thanks to the embedding mechanism.
Since the secret message is hidden, it seems to be an ordinary file to the untrained eye. Todd uses the same steganographic approach to retrieve the hidden message from the target after receiving it. To provide additional protection, a key is often used in conjunction with the steganographic process. Todd would use the same key to extract the hidden message if Erin uses this additional security measure.
What Is Cryptography?
Cryptography is the process of encrypting data by converting it into an unreadable format using mathematical principles and algorithms. Public or private key cryptography is used to encrypt the info. The same key is used to encrypt and decrypt a message in public key (or symmetric key) cryptography. Different keys — a public and a hidden key that are mathematically identical to each other — are used in private key (or asymmetric key) cryptography.
The below are the prime goals of modern cryptography:
- Trustworthiness. Integrity can’t decrypt the hidden letter (or ciphertext) since it was sent to someone who wasn’t expecting it. The message transmitted must be sent to the recipient unaltered, or the alteration must be identified at the very least.
- Non-repudiation is a term that refers to a person’s refusal to The sender cannot later deny transmitting the letter, and the receiver cannot later deny receiving it.
- Authentication is the process of verifying someone’s identity. The sender and receiver will verify each other’s identities as well as the message’s origin and destination.
So, what’s the difference between steganography and cryptography, after all of this?
Steganography vs Cryptography
Steganography is often confused with cryptography because both the techniques intend to keep your data private from prying eyes. The ways they achieve said goals, however, are very different:
- With cryptography, any eavesdropper will know that the information you’re exchanging has been encrypted and rendered unreadable without knowing the secret decryption key.
- Steganography, on the other hand, camouflages your data and transmits it using seemingly innocuous carrier media to prevent snoops from knowing that a secret exchange is taking place.
|Basis for Comparison||Steganography||Cryptography|
|Goal||Conceals the occurrence of any exchange between parties to facilitate secret communication.||Encrypts the contents of visible communications to protect the data.|
|Concealment Tactic||The embedded message is invisible to an unaware observer.||The encrypted message is indecipherable to anyone without the decryption key.|
|Supported Security Principles||Confidentiality and authentication||Confidentiality, data integrity, authentication, and non-repudiation|
|Implementation Techniques||Spatial domain, transform domain, distortion, etc.||Asymmetric key encryption, symmetric key encryption, etc.|
|Counter Steps||Use rigid protocol specifications, data sanitizationMonitor data exchanges, perform analyses that include looking for structural oddities suggestive of manipulation||Use reverse engineering to break complex algorithms Implement cryptography export laws that prohibit the transfer of such devices or technology between countries|
Tools for Steganography
Let’s take a look at some steganography methods. We’ll talk about how they’re used to mask and relay information across files and media invisibly.
Xiao Steganography is a free application with a user-friendly gui. You may use this programme to hide your hidden messages inside BMP or WAV files. All you have to do is instal a WAV or BMP file as the messenger, then the hidden file you want to hide. It supports RC4, Triple DES, and hashing as encryption algorithms. From the list, choose the algorithm you want to use and save the stego-medium. The recipient would continue to use the same technique to decode it.
Steghide is an open-source command-line programme that allows you to mask your message in an image or audio file.
After changing the file extensions as needed, use the following command to insert your hidden message into a carrier file:
> steghide embed -cf image.jpg -ef secret.txt
On the receiver’s end, to extract the secret image, run the following command:
> steghide extract -sf image.jpg
To view additional info on the file received, before proceeding to extract it, you can execute the command as follows:
> steghide info image.jpg
Note: This tool accepts input in the form of JPEG, BMP, WAV, and AU, and the embedded message is not limited to text. It uses Rijndael’s algorithm, a block cipher with a key size of 128 bits, and it’s recommended for Mac and Linux users.
Crypture is a command-line interface that takes BMP as an input file and hides your messages within it. The BMP image file must be eight times bigger than the hidden data file, for example. On the plus side, the programme is just 6 KBs in size and does not entail any download.
SSuite Picsel Security
SSuite Picsel is a free lightweight standalone tool for steganography that is part of the SSuite office applications suite. Using a different technique that uses image files as keys, you can use this method to mask text inside image files. In addition to the image file containing the hidden code, another image file is used as a key for encryption rather than a password. It takes BMP, JPG, JPEG, and WMF files as input.
DeepSound is an audio steganography application that allows you to conceal or remove hidden messages from audio files or CD tracks. To boost data security, it also supports AES-256 encryption. The programme also includes an easy-to-use audio converter module that supports FLAC, MP3, WMA, WAV, and APE, among other audio formats.
Alternative techniques include StegoMagic, OpenPuff, Netcross, and others.
How do we know when messages are concealed using steganography now that we’ve looked at how to hide information? Steganalysis is a subfield of knowledge concealment that does only that. This procedure aims to detect suspicious packages, decide if they contain secret payloads, and try to retrieve them if possible. Steganography and steganalysis are basically two sides of the same coin: the former hides information, while the latter detects and recovers it.
Steganalysis can be performed using a variety of methods and techniques, but they can be narrowly divided into two types: targeted (or specific) steganalysis and blind (or universal) steganalysis. The targeted steganalysis approach is completely reliant on the steganographic algorithm that is used to hide the hidden data, while the processes of blind steganalysis are unaffected by the underlying algorithm. Visual, statistical, and systemic attacks are all forms of targeted steganalysis.
Here are some resources to look at if you want to try your hand at steganalysis:
- StegExpose is a steganalysis instrument that specialises in LSB steganography (LSB stands for “least important bit”) identification and quantitative steganography. It has a command-line interface which can detect distortion of lossless images like PNG and BMP. It analyses photographs in bulk and generates reports and customizations that make it easier for non-forensic users to use.
- Niels Provos, a security researcher, developed the steganalysis tool Stegdetect. StegoHunt is a commercially available commodity that can be used as a substitute.