Security Features on and with Documents: A Survey

Image Scrambling is a part of data security and comes under the concept of data hiding. This means that the images, when scrambled, remain safe and secret from malicious sources. This would, in turn, keep the data scrambled and can be taken only by valid people.

Today, this has become a part of cryptography, even though it is not definitely encryption through an algorithm.

Ref. [1] suggested that image scrambling can be used in real time to safeguard data and gave us examples of Sudoku puzzles and Rubik’s cubes. Here, the image matrix is obtained and scrambled, which results in a matrix that is very different from the original image. Then, when this image is unscrambled, the original image is returned.

Ref. [2] Concludes that Image scrambling can be done two-way using the Arnold transform algorithm. Arnold transform can be confusing at times due to its complexity.

The Arnold transform algorithm processes under the concept where the n numbers of iterations are performed, and n is used as the key. The image is encrypted by shuffling the planes simultaneously. This has been done numerous times.

The Sudoku pairs are used to scramble blocks here and are then used as a part of Image Scrambling.

This is a set of bits arranged corresponding to a given bit position (MSB or LSB types) in a binary number representing signals. A Bitplane is meant to be regarding a discrete digital signal. For instance, audio or video forms may be taken.

The Most Significant Bit can be the most effective one with higher or critical approximation values of the plane, and LSB-Least Significant Bit would give us the lower values. Image Scrambling is also used here. This would mean that the Planes of an image are changed and then those bits are used as a key for the encryption of the original image.

Ref. [3] Suggested a new bit-plane decomposition algorithm using Image Scrambling where the result is received. This would mean that any image similar to the source image is taken, and bit plane methodology is used for decomposition of that image. It is then used as the key for the encryption. The Plane that can be used as a key can be decided by the user themself.

Ref. [4] Concluded that Arnold scrambling, a technique that uses the Arnold transform algorithm, and Bit Scrambling, which is performed as Bit Plane Decomposition, can be used for the encryption and decryption process.

The former is said to be simpler and easier to workout than the latter since Arnold Scrambling becomes somewhat confusing. Image Scrambling is generally a topic that is more common and known than Arnold Scrambling.

Here, the bit plane with a number of Most Significant bits would contribute more when compared to the Least Significant ones. This is because the Most Significant ones are of larger intensity.

Steganography is the technique of concealing a message inside another or even more in a new format itself.

Here, one can conceal a new message within another one where the message that is visible may be unimportant, or the concealed message may be offensive or critical. These concealing may be done in both audio and video files. Most recent examples of these uses are Micro-Ink, which would be very small, like 1cm in diameter.

Ref. [5] uses an approach where for encryption Caesar cipher and Vigenère cipher are used to get the encrypted data. They are then combined with the hash function for Steganography purposes. This would lead to an increase in speed and security when compared to the other methods of LSB Image Steganography algorithms.

The Fig. 1 would give us a general example of how data can be embedded into an image for Security features.

Figure 1.

Indian Rupee with its features that are highlighted

It shows Indian Currency and its Security features. The Indian currency has various security features such as:

• Color Shifting ink when it is exposed to light.

• Microprint of the currency value.

• RBI written on the Spectacles of Mahatma Gandhi, which is not visible to the naked eye.

• Some other typographic unique features that cannot be duplicated easily.

• Numbers written in Braille script.

• Raised-up print that is shown at a certain angle.

• The watermark of Mahatma Gandhi and electrolyte numerical of the currency written

Out of these features, almost four or five are part of Steganography. It has its basics here, and hence, any data can be embedded into an image.

It means sending a message through a secured channel by encrypting it using a code, which is later decrypted by using another code. The code used is called a key.

In Cryptography, there are various algorithms that are commonly used. Some are the AES, DES, and RSA. In each and every algorithm, the process of encrypting and the number of rounds of encryption varies. As well as the way the encryption is done.

For example, in AES, there 13 rounds of process which would result in encrypting the whole data. For decryption, the same method is used, but with the reversing of the processes done.

Ref. [6] Uses Image encryption techniques and channel coding. Chaotic maps are used here that are based on Cryptography. They give us a wide range of Security and would help in real-time data more.

Figure 2 shows us the general concept of Cryptography. It branches out to various other methods of cryptography as well later on. The image depicts how plain text by the sender is encrypted using a Public key to make it Cipher text.

Figure 2.

Cryptography concept

The Decryption is done using the same key that is made Private such that only the receiver knows about that. Once the decryption is done, the original text is received back by the Receiver. In the mean while all the other ways used to decode the encrypted text would result in error only.

Blockchain is defined as a mathematical structure that can store data corresponding to a particular detail or the component specified.

From Refs. [7,8,9,10], which are based on the concept of Blockchain and its various methods of implementation, it can be concluded that Blockchain is becoming a trending technology while using medical images nowadays. Physicians would like to see the various stages of improvement or the disease of a patient along with the comments or descriptions given to them respectively. Refs. [11, 12] also adds that Blockchain would mean that the data is safe and can be viewed only by the necessary person.

Ref. [13] tells us about how to encrypt an image securely using Blockchain. Here, the images are scrambled and random permutation is used and blocks are obtained.

These blocks are later mapped with cipher blocks. The Blockchain is obtained using the SHA-512 hash. That is later embedded in covering audio signals for enhanced protection.

Here, the image is taken first and encrypted and then the Block permutation is performed on that for shuffling them. Later the data is embedded that needs to be sent along with the image.

Once the receiver gets the specified data, they need to decrypt them first to get the data and the image separately, after which the data is kept secret as it is, and after reversing the process of encryption, the original image is returned as supposed.

When it comes to accuracy, Cryptography and blockchain technology can be considered, as they are the latest and most used.

When considering both of them together, the accuracy tends to be higher than when they are taken separately. The rest of the technologies also give us the result, but the accuracy rate tends to lessen them.

The efficiency would depict as to which level can the result be accepted and dependency of the technologies.

As seen in Table 2, the efficiency of Blockchain is higher when other technologies, such as Steganography and Scrambling, are involved. Cryptography gives us much higher one compared to Steganography.

This is because the latter one was used from olden times and cryptography gives the latest version.

The reliability would tell us how reliable the results are. When compared using various algorithms of the above-mentioned technologies, Cryptography has a wide range of algorithms that perform well and have more recent updates. This holds good for Blockchain as well.

This is one of the most important metrics that needs to be checked. Security is provided through all the technologies since they are basically used for encryption purposes only. But the level differs. Blockchain would provide security for the data and cryptography uses algorithms for that. Some of these algorithms are complex, which would make it difficult for them to be processed at the earlier stages.