Modified Playfair cryptosystem for improved data security

Abstract

Playfair is the earliest known classical block cipher which is capable of taking two characters as a unit in the process of encryption and decryption. However, the cipher is suffering from vulnerability to many cryptanalysis attacks due to a lack of confusion and diffusion properties, an inability to handle numbers and special characters in the process of encryption and decryption, and a host of other deficiencies. Although several modifications and improvements had been done by different researchers, the emphasis has been on the modification of the key matrix to accommodate more characters to increase the keyspace. No attention has been given to increment in the size of the block that the Playfair cipher can handle at a time. In this paper, a modified Playfair (MPF) cryptosystem that is capable of handling different block sizes with high diffusion and confusion properties is developed. cryptanalysis of the developed cryptosystem was carried out and the results show that the MPF cryptosystem is resistant to Known plaintext attack, chosen-plaintext attack, chosen ciphertext attack, frequency analysis attack, autocorrelation attack, differential cryptanalysis attacks, entropy attacks, brute force attack, and can handle variable block sizes.

A Lightweight Image Cryptosystem for Cloud-Assisted Internet of Things

“…Confusion and diffusion constitute the two vital features of cryptography techniques [25,26]. Researchers use substitution boxes (S-boxes) to achieve the confusion property [27], while the bit permutation technique is normally used to achieve the diffusion property [28]. However, the use of an S-box increases the demands for memory (for storage) and computing power (for production) [29].…”

Efficient Mapping Scheme for Elliptic Curve Cryptosystem in a Multiprocessing Environment

“…Algorithm 4: Reshuffling of bits during Reverse mapping Process [49] Module ReshuffleforReversemapping(ctext, secretkey) Output: plaintext[1…”

“…Pseudocode for Reshuffling bits (adopted from[49])Module Reshuffleformapping( mtext, secretkey) Output Atext[1..C]: 1D array of bits Variables Integer: k, col, x, C msg[1..C]: arrays of bits START LET C = LENGTH(mtext) INITIALIZE msg as empty array LET k = 1 FOR col = 1 TO C LET x = secretkey[col] LET msg( k) = mtext[x] LET k = k + 1 END LET atext = mtext DISPLAY atext STOP…”