Abstract: The Hill cipher is resistant to brute-force and statistical attacks, but it can be broken with a known plaintext-ciphertext attack (KPCA). In this paper, we propose a modification of the Hill cipher, HCM- PRE, which is still resistant to brute-force and statistical attacks, and is resistant also to KPCA due to dynamic encryption key matrix generating. With the modification, the new HCM-PRE can be applied widely in the systems which need high security (e.g., image encryption). Experimental results show that the proposed modification is significantly more effective in the encryption quality of images than original Hill cipher and its known modifications (HCM-PT, HCM-H, HCM-HMAC, and HCM-EE) in the case of images with lar ge single colour areas, and slightly more effective otherwise. HCM-PRE is about two times faster than HCM-EE and HCM-HMACand four times faster than HCM-H in the frame of our experiments.

Abstract: Protecting data from malicious attacks during storage and transmission is the reason for using encryption. Encryption can be achieved by two methods – Transposition and Substitution. Transposition refers to changing the order of characters in a given text. On the other hand, substitution is the process of replacing each character of the plaintext with some other character. Using a combination of transposition and substitution for encryption leads to greater security when compared to using either of them separately. Vigenere Cipher is a poly-alphabetic cipher. It is based on the substitution technique which uses multiple substitution alphabets. In this paper, we introduce double columnar transposition on Vigenere Cipher to enhance its security making cryptanalysis difficult.

Abstract: Before the invention of computers, cryptography was mainly concerned with textual patterns. Nowadays, this emphasis has shifted and cryptography now makes extensive use of different fields including bioinformatics. The fundamental idea behind the cipher presented here is to transform any kind of binary message; such as text, sound tracks, and even images, into the form of a single-stranded DNA sequence. Subsequently, digraphs of codon triplets are encrypted using a grid of 8x8 codon matrix that is randomly constructed according to some secret key. Although the encryption/decryption rules were kept almost the same as the classical 5x5 Playfair, using the DNA encoding step makes it almost impossible for an attacker to perform a frequency analysis on that vast number of character digraphs. Furthermore, an interweaving step is added to scramble the encrypted sequence offering more randomness. When compared with other modifications of the Playfair cipher, the proposed method showed a number of advantages including the ability to cipher any type of digital media, the elimination of plain-text preprocessing step, and the applicability to be integrated into larger security systems such as DNA steganography. Furthermore, due to the very weak correlation between cipher-data and original message, the proposed method shows a strong robustness against cipher attacks.

Abstract: When it comes to information hiding it is always a question whether to use Steganography or cryptography. Cryptography scrambles the message so that is it unrecognizable and without proper key the Encrypted message is useless. With the help of steganography messages can be passed over the network discreetly as it provides secure data hiding. It is very challenging and emerging field of research. Steganography can be simple as LSB technique or can be complicated as transform domain techniques, each technique have their own advantage. Both of these techniques are often confused with each other because in a way both are used to hide data. This paper discusses the important aspects of Steganography and Cryptography. How a simple LSB steganography technique in images can be complicated further using combination of Cryptography and Pseudo-random number generator.

Abstract: A format-preserving cipher including an encryption and a decryption scheme supporting non-linear access to input data by allowing the selection of portions of data from a potentially larger dataset to be encrypted, thus avoiding a necessarily sequential access into the input plaintext data. The cipher first defines a forward mapping from the allowable ciphertext values to an integer set of the number of such allowable ciphertext values, and a corresponding reverse mapping. It also supports exclusion of a certain set of characters from the ciphering process. Further, the encryption algorithm can encrypt the input plaintext data while preserving its original format and length and a corresponding decryption algorithm. The cipher advantageously embodies the encryption and decryption of multi-byte values or strings of data, thus fitting a variety of industrial needs.

Abstract: A variable-length block cipher apparatus and method capable of format preserving encryption are disclosed. An encryption device for a variable-length block cipher apparatus includes an encryption key generation unit configured to generate encryption round keys eRKo, eRK 1 ,..., eRK Nr using a secret key and the number of rounds Nr, and a ciphertext output unit configured to output ciphertext having a length identical to that of plaintext using the plaintext and the encryption round keys. 7. A decryption device for a variable-length block cipher apparatus includes a decryption key generation unit configured to generate decryption round keys dRK 0 , dRK 1 ,..., dRK Nr using a secret key and a number of rounds Nr, and a plaintext restoration unit configured to restore ciphertext into plaintext having a length identical to that of the ciphertext using the ciphertext and the decryption round keys.

Abstract: Data transmission has become very common in human's daily life. This data transmission can be confidential or the data may be intended for a section of people. The data that is intended to be transmitted to a particular recipient should be read only by the corresponding person and not anyone else. For this reason, the best way to protect the data is by encryption. This provides security from stealing of data. This paper deals with a mechanism to encrypt a data using flip-flops and double substitution method. The basic idea to obtain blocks of plain text and then use T-flip-flops along with double substitution to result in a convincing cipher text. The result is a cipher text obtained by using plaintext itself for encryption. This algorithm can be used to transmit bit sequence of any length, thus ensuring the usage of bandwidth to desirable level. This method may result in an Electronic Code Book (ECB). The keys used will be asymmetric. The receiver just follows the steps in reverse order to retrieve the data or plaintext from the received cipher text.

Abstract: Character type cipher is always used in web application system and can be deciphered by the illegal users through "run dictionary", so, a new random encryption algorithm for character type cipher is put forward in this paper. The encryption parameters are randomly generated in the algorithm, and random confusion is adopted in the cipher text structure, so the same plaintext can produce different ciphertexts.the experimentation shows that the algorithm is feasibility and validity.

Abstract: In this analysis, we have developed an asymmetric b lock cipher which is involving a key bunch matrix A ( = [a ij ]) in the process of encryption, and B ( = [b ij ]) in the process of decryption. The keys a ij are used as powers of the plaintext elements, and the keys b ij are used as the powers of the ciphertext elements. Here , we have made use of Euler’s totient function and Euler’s theorem in the development of the cipher. The cryptanalysis clearl y shows that the strength of the cipher is quite significant.