Network security has become a crucial part of the modern communication system. The need for network security was arisen to sustain the confidentiality and integrity of the data and guard it against the unauthorised access. The steganography and cryptography are the two sides of a coin where the steganography hides the traces of communication while cryptography uses encryption to make the message incomprehensible.
The steganography does not employ changes in the structure of the message. On the other hand, the cryptography alters the standard secret message structure when transferred along the network.
Content: Steganography and Cryptography
|Basis for comparison||Steganography||Cryptography|
|Basic||It is known as cover writing.||It means secret writing.|
|Goal||Secret communication||Data protection|
|Structure of the message||Not altered||Altered only of the transmission.|
|Popularity||Less popular||More commonly used.|
|Relies on||Key||No parameters.|
|Supported security principles||Confidentiality and authentication||Confidentiality, data integrity, authentication, and non-repudiation.|
|Techniques||Spacial domain, transform domain, model-based and ad-hoc.||Transposition, substitution, stream cipher, block ciphers.|
|Implemented on||Audio, video, image, text.||Only on text files.|
|Types of attack||Steganalysis||Cryptanalysis|
Definition of Steganography
Steganography is a technique of hiding the communication by concealing the secret message into a fake message. The term steganography has Greek influences which means “covered writing”. The main idea behind the steganography is to prevent the suspicion about the existence of the information.
Earlier, invisible ink, pencil impressions on the handwritten characters, small pin punctures are the methods used to hide the message. Simplest technique of hiding a message is to create a message in which only a few significant characters contains the secret message.
The steganography technique involves a cover carrier, secret message, stego key and stego carrier. Text, audio, image and video behaves as cover carriers which contain the hidden information embedded in it. Stego carrier is generated using a cover carrier and embedded message. Stego key is also used as supplementary secret information like a password used by the recipient to extract the message.
Forms of steganography –
Text: In this steganography, the text can be used as a cover media. To hide the message a word or line can be shifted; whitespaces can be used, even the number and position of the vowels are utilised to conceal the secret message.
Audio: Audio stenography can conceal the secret message in the audio file with the help of its digital representation. It can be achieved easily as a typical 16-bit file has 216 sound levels, and a few levels difference could not be detectable by the human ear.
Video: Video steganography brings more possibilities of disguising a large amount of data because it is a combination of image and sound. Therefore, image and audio steganography techniques can also be employed on the video.
Image: It is the most pervasively used form of steganography, the reason behind this is that it causes least suspicion.
The main disadvantage of using the steganography is a significant amount of overhead it produces for hiding a small amount of information. Additionally, the system must not be discovered otherwise it is useless.
Definition of Cryptography
The cryptography provides several encoding schemes for achieving the security while communicating in a public network. The word cryptography originated from a Greek word, which signifies “secret writing”. The cryptography can be understood by an example, where a sender sends a message which initially exists in the plaintext. Before the transmission of the message over the network, it is encrypted and converted into the ciphertext. When this message is received at the receiver’s end, it is again decrypted back into the plaintext.
Types of the cryptography –
Symmetric key cryptography (Secret key cryptography): This type of cryptography uses a key for encrypting and decrypting the plain text and cipher text respectively. The only condition here is that it shares the same key for the encryption and decryption and it also consumes less execution time.
Asymmetric key cryptography (Public key cryptography): This scheme uses two keys named as a private key and public key. The public key is provided by the receiver to the sender to encrypt the message while the private key is applied by the receiver itself to decrypt the message. The keys can be reused with other entities.
Key Differences Between Steganography and Cryptography
- The meaning of the steganography is “covered or hidden writing” while cryptography signifies “secret writing”.
- Steganography is an attempt to achieve secure and undetectable communication. On the other hand, cryptography intends to make the message readable for only the target recipient but not by others through obtaining a disguised form of message.
- In steganography, the main structure of the message is not changed whereas cryptography imposes a change on the secret message before transferring it over the network.
- The cryptography is prevalently used unlike steganography, which is not so familiar.
- The degree of the security of the secret data is measured by the key length which makes the algorithm strong and unbreakable. Conversely, there is no such thing in steganography.
- Steganography provides only confidentiality and authentication. On the contrary, the principles of security provided by the cryptography are confidentiality, integrity, authentication, and non-repudiation.
- Spacial domain, transform domain embedding and model-based are some of the algorithms used in steganography. In contrast, the cryptography uses techniques named as transpositional, substitution, stream and block ciphers.
- The steganography can be employed on any medium such as text, audio, video and image while cryptography is implemented only on the text file.
- The reverse engineering employed to decode the message in cryptography is known as cryptanalysis. As against, the technique used to detect the presence of the steganography is known as steganalysis.
Steganography is the science deals with how communication can be disguised while cryptography is the science of transforming the content of the communication and making it obscure. It also implies the difference between breaking the system, the steganography is defeated if the presence of steganography is disclosed, whereas in cryptography the attacker must not be able to read the secret message otherwise the system is broken. The security of the steganography depends on the secrecy of the data encoding system.