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: Cryptography is a science of converting clear message into secret message "nonreadable message", where message was encrypted at sender side then decrypted at receiver side Vigenere is an example of substitution cipher, it has various limitations, in this paper we propose an advanced encryption algorithm which improves the security of Vigenere method by combining it with modern cipher method like Stream cipher, Stream cipher relatively regards as unbreakable method, and it uses binary form (instead of characters) where the Plaintext, Ciphertext and the Key are strings of bits When applying the proposed algorithm, we see that the mentioned above combination cipher has a high degree of security, where cipher based on just Vigenere method is not secure Also, the proposed algorithm makes the cryptanalysis, using frequency attack, more difficult General Terms Information security, cryptography

Abstract: Quantum Enigma Cipher is an epoch-making concept in the cryptography that may break the Shannon limit of the cryptography. Yuen-2000 (Y-00) protocol is a first generation toward the Quantum Enigma Cipher that overcomes the Shannon limit in cryptography relying on macroscopic quantum effects. Current Y-00 cipher is an encryption scheme where noise masking blocks an eavesdropper's reading of the physical ciphertext consisting of the mathematical structure. No such masking effect is realized only by using the mathematical encryption, because mathematical ciphertexts are composed of binary signals, "0" or "1" or deterministic symbols, and they are correctly discriminated. Y-00 cipher is one of the candidates to provide high transmission performance and a provable security simultaneously in the real world. In our present, Y-00 cipher, mathematical cipher and physical phenomena are combined. It features multi-level signaling by mathematical cipher and noise masking to hide the ciphertext in the quantum noise and other channel noise. In the paper, transmission performance of Y-00 cipher is experimentally investigated. A running test for 60 days of Y-00 cipher transceiver at 2.5 Gbit/s is demonstrated. In addition, a trial of a current direct modulation scheme using 4096 signal levels for realizing a compact Y-00 transceiver is demonstrated. Furthermore, a wavelength-division multiplexing transmission of Y-00 cipher is experimentally demonstrated, and 100-Gbit/s Y-00 cipher transmission is successfully transmitted over 120 km.

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: In this paper, we have proposed an encryption method which is developed by extending Playfair Cipher to make it more secure. Known as Polyalphabetic cipher, Playfair uses a key matrix containing 25 characters for encryption. This extended playfair cipher supports all 26 characters filled in two different key matrices, second matrix having extra checksum characters. As Playfair is susceptible to various attacks, so to avoid that, we included rotation operation on key matrices and swapping of rows and columns of key matrices according to randomly generated swap patterns. Cryptanalysis of new proposed extended cipher is done by performing various attacks and we conclude that this technique is more secure and can be used as a part of advanced encryption algorithms like AES, DES.

Abstract: We propose two stream ciphers based on a non-secure pseudorandom number generator (called the mother generator). The mother generator is here chosen to be the Mersenne Twister (MT), a widely used 32-bit integer generator having 19937 bits of internal state and period 219937 − 1. One proposal is CryptMT, which computes the accumulative product of the output of MT, and use the most significant 8 bits as a secure random numbers. Its period is proved to be 219937 − 1, and it is 1.5-2.0 times faster than the most optimized AES in counter-mode. The other proposal, named Fubuki, is designed to be usable also as a block cipher. It prepares nine different kinds of encryption functions (bijections from blocks to blocks), each of which takes a parameter. Fubuki encrypts a sequence of blocks (= a plain message) by applying these encryption functions iteratedly to each of the blocks. Both the combination of the functions and their parameters are pseudorandomly chosen by using its mother generator MT. The key and the initial value are passed to the initialization scheme of MT.

Abstract: In this paper, a new extension of the Playfair cipher algorithm is proposed to encrypt image data more securely. The proposed method constructs a 16×16 secret key matrix to scramble image data byte by byte. In addition, the algorithm complexity is increased using masking and XOR procedure. That is, the key is used to generate a mask that is subsequently XORed with the scrambled image. Experimental results showed that using two slightly different secret keys, the resultant encrypted images are still completely different.

Abstract: Cipher is a first polygraphic substitution cipher that works on digraphs, trigraphs (3 letter squares) or hypothetically blocks of any magnitude. The Hill Cipher utilizes a region of science called Linear Algebra, and specifically requires the client to have a rudimentary knowledge of matrices. It additionally makes utilization of Modulo Arithmetic (like the Affine Cipher). To perform decryption, the hill cipher requires the inverse of the key matrix. This is the major shortcoming of Hill cipher since every key matrix is not invertible. We will propose a new variant of hill cipher, which will find the decryption of the cipher text even when the key matrix is non invertible.

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: One of the well-known digraph substitution cipher is the Playfair Cipher. It secures information mathematically by mangling message with key. The privacy of intended sender and receiver information is protected from eavesdropper. However the original 5 x 5 Playfair Cipher can support only 25 uppercase alphabets. Here we have implemented a new technique which includes a rectangular matrix having 10 columns and 9 rows and six iteration steps for encryption as well as decryption purpose. This 10 x 9 rectangular matrix includes all alphanumeric characters and some special characters. Cryptanalysis is done to show that the modified cipher is a strong one. Finally we have implemented this concept with the help of MATLAB.

Abstract: We present a new, misuse-resistant scheme for online authenticated encryption, following the framework set forth by Fleischmann et al. (FSE 2012). Our scheme, COBRA, is roughly as efficient as the GCM mode of operation for nonce-based authenticated encryption, performing one block cipher call plus one finite field multiplication per message block in a parallelizable way. The major difference from GCM is that COBRA preserves privacy up to prefix under nonce repetition. However, COBRA only provides authenticity against nonce-respecting adversaries. As compared to COPA (ASIACRYPT 2013), our new scheme requires no block cipher inverse and hence enjoys provable security under a weaker assumption about the underlying block cipher. In addition, COBRA can possibly perform better than COPA on platforms where finite field multiplication can be implemented faster than the block cipher in use, since COBRA essentially replaces half of the block cipher calls in COPA with finite field multiplications.

Abstract: The block cipher used in the Chinese Wireless LAN Standard (WAPI), SMS4, was recently renamed as SM4, and became the block cipher standard issued by the Chinese government. This paper gives a method for finding the linear approximations of SMS4. With this method, 19-round one-dimensional approximations are given, which are used to improve the previous linear cryptanalysis of SMS4. The 19-round approximations hold with bias 2−62.27; we use one of them to leverage a linear attack on 23-round SMS4. Our attack improves the previous 23-round attacks by reducing the time complexity. Furthermore, the data complexity of our attack is further improved by the multidimensional linear approach.

Abstract: The Hill cipher algorithm is one of the symmetric key algorithms that have many variations but still not suited for all zeroes plaintext block. Chosen-plaintext attack can be possible on Toorani and Falahati Hill Cipher Algorithm by two closely related variants of Hill Cipher. In this paper we have presented a new approach of Hill Cipher (RDHill Cipher) using DNA cryptography and TFHill Cipher to overcome the drawbacks of TFHill. We implement this algorithm for image encryption in which firstly the image will be converted into binary value and the nibble of binary value will be rotated, then it will be converted into DNA, and then DNA to Amino Acids. Secondly TFHill Cipher can be applied on Amino Acids. The output is measured for the security level based on Correlation, histogram and entropy. The experimental results showed that the combination technique resulted in a higher entropy value and lower correlation, and a more uniform histogram, compared to the Hill Cipher, affine Hill, TFHill and SVK Hill Cipher. This implies the good quality of the retrieved image compared to the original one.

Abstract: Cryptography comes from the Greek words for "secret writing". The plain text is encrypted into the corresponding cipher text, using an algorithm and a key. Substitution and Transposition are two techniques used for converting data into non-readable form. Caesar Cipher is an example of substitution technique. In this paper we have proposed a cipher that uses basic encryption techniques of substitution and transposition. A single columnar transposition followed by a double substitution is applied on a Caesar cipher in order to make it a stronger and a more secure cipher.

Abstract: Manual analysis and decryption of enciphered documents is a tedious and error prone work. Often—even after spending large amounts of time on a particular cipher—no decipherment can be found. Automating the decryption of various types of ciphers makes it possible to sift through the large number of encrypted messages found in libraries and archives, and to focus human effort only on a small but potentially interesting subset of them. In this work, we train a classifier that is able to predict which encipherment method has been used to generate a given ciphertext. We are able to distinguish 50 different cipher types (specified by the American Cryptogram Association) with an accuracy of 58.5%. This is a 11.2% absolute improvement over the best previously published classifier.

Abstract: Cryptography is an art and science of converting original message into no readable form. There are two techniques for converting data into no readable form. Transposition technique, Substitution technique. In recent years there is drastic progress in Internet world. Sensitive information can be shared through internet but this information sharing is susceptible to certain attacks. Cryptography was introduced to solve this problem. Cryptography is art for achieving security by encoding the plain text message to cipher text. Substitution and transposition are techniques for encoding. When Caesar cipher substitution, Rail fence cipher and Columnar Transposition Cipher techniques are used individually, cipher text obtained is easy to crack. This Paper will present a perspective on combination of techniques like Rail fence and colounar transposition with one time pad cipher. One Time Pad is an example of substitution method. In this paper I will presented how to improve security of One Time Pad Cipher to make it more secure and strong by Its implementation with Rail fence and columnar transposition cipher

Abstract: Cryptography is a science that applies complex mathematics and logic to design strong encryption methods. Achieving strong encryption, the hiding of data's meaning, also requires perceptive leaps that allow creative application of known or new methods. So cryptography is also an art. We can say now that Cryptography is the art of achieving security by encoding messages to make them non-readable. Cryptography, as the most important aspect in the never ending evolving information technology era, is being criticized in its aspect. Information outbreaks make users doubtful on relying on their own information in current cryptosystems. Cryptography is used to maintain the secrecy and integrity of information, whenever it is exposed to potential attacks. Cryptography comes from the Greek words for "secret writing". The plain text is encrypted into the corresponding cipher text, using an algorithm and a key. Substitution and Transposition are two Techniques used for converting data into non-readable form. Rail Fence Cipher is an example of Transposition technique. In this paper we have proposed a cipher that uses basic encryption techniques of substitution and transposition. A double columnar transposition followed by a double substitution is applied on a Rail Fence cipher in order to make it a stronger and a more secure cipher.

Abstract: We present a new, misuse-resistant scheme for online authenticated encryption, following the framework set forth by Fleischmann et al (FSE 2012) Our scheme, COBRA, is roughly as efficient as the GCM mode of operation for nonce-based authenticated encryption, performing one block cipher call plus one finite field multiplication per message block in a parallelizable way The major difference from GCM is that COBRA preserves privacy up to prefix under nonce repetition However, COBRA only provides authenticity against nonce-respecting adversaries As compared to COPA (ASIACRYPT 2013), our new scheme requires no block cipher inverse and hence enjoys provable security under a weaker assumption about the underlying block cipher In addition, COBRA can possibly perform better than COPA on platforms where finite field multiplication can be implemented faster than the block cipher in use, since COBRA essentially replaces half of the block cipher calls in COPA with finite field multiplications

Abstract: Light weight block cipher algorithms are vital for constrained environment. It is easy to propose an algorithm that optimize any two factors like (security and cost), (security and performance) and (cost and performance) but it is difficult to optimize three factors together at the same time. In this paper, we propose a new lightweight block cipher algorithm called OLBCA. PRESENT lightweight block cipher algorithm is chosen because it is one of the most common and famous lightweight algorithms. Also, the International Organization for Standardization and the International Electro technical Commission (ISO/IEC 29192-2:2012) declared that PRESENT as a new international standard for lightweight cryptographic methods. We applied three attacks differential, integral attacks and boomerang attack. The results showed that OLBCA is better than PRESENT algorithms in three factors.

Abstract: In order to secure the information there are different polyalphabetic substitution ciphers are available. Out of these Vigenere cipher is considered to be most efficient and simplest one. Due to its repeating nature of the key it is also vulnerable to attacks. To overcome this, there are many researches going on to modify the conventional Vigenere Cipher. In this paper we have presented a review of recent modifications in Vigenere cipher and its cryptanalysis.

Abstract: Generally, the present disclosure provides technology modifying a first cryptographic cipher with one or more operations of a second cryptographic cipher. In some embodiments the technology leverages a mathematical relationship between representations of data used in the first and second ciphers to enable the substitution of one or more operations of the first cipher with one or more operations of the second cipher. The resulting modified cipher may in some instances exhibit improved performance and or security, relative to the unmodified first cipher. Methods, computer readable media, and apparatus including or utilizing the technologies are also described.

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: Nowadays, the use of mobile communication systems are growing increasingly across the world, huge sensitive information exchanging over these systems. The security problems of information confidentiality, authenticity, and integrity became a prime concern of issue for users and society. Symmetric cryptographic algorithms have been proposed to protect the information of the senders and receivers through mobile systems. There are various symmetric cryptographic algorithms such as KASUMI cipher, SNOW cipher, ZUC cipher, and AES cipher have been developed for achieving secure mobile communication systems. Some cryptanalysis techniques (e.g. Sandwich Cryptanalysis Technique, Sliding Property Technique, Differential Cryptanalysis Technique, and Biclique Cryptanalysis Technique) can be used to attack these symmetric ciphers, therefore there is a need for more analysis studies to address the security problems of these ciphers. This paper presents a comparative study of these symmetric ciphers with focus on analysis of their specifications, components, and some cryptanalysis techniques over each other.

Abstract: The Lai-Massey scheme, proposed by Vaudenay, is a modified structure in the International Data Encryption Algorithm cipher. A family of block ciphers, named FOX, were built on the Lai-Massey scheme. Impossible differential cryptanalysis is a powerful technique used to recover the secret key of block ciphers. This paper studies the impossible differential cryptanalysis of the Lai-Massey scheme with affine orthomorphism for the first time. Firstly, we prove that there always exist 4-round impossible differentials of a Lai-Massey cipher having a bijective F-function. Such 4-round impossible differentials can be used to help find 4-round impossible differentials of FOX64 and FOX128. Moreover, we give some sufficient conditions to characterize the existence of 5- , 6- , and 7round impossible differentials of Lai-Massey ciphers having a substitution-permutation (SP) F-function, and we observe that if Lai-Massey ciphers having an SP Ffunction use the same diffusion layer and orthomorphism as a FOX64, then there are indeed 5- and 6-round impossible differentials. These results indicate that both the diffusion layer and orthomorphism should be chosen carefully so as to make the Lai-Massey cipher secure against impossible differential cryptanalysis.

Abstract: Stream ciphers are symmetric key cryptosystems that are used commonly to provide confidentiality for a wide range of applications; such as mobile phone, pay TV and Internet data transmissions. This research examines the features and properties of the initialisation processes of existing stream ciphers to identify flaws and weaknesses, then presents recommendations to improve the security of future cipher designs. This research investigates well-known stream ciphers: A5/1, Sfinks and the Common Scrambling Algorithm Stream Cipher (CSA-SC). This research focused on the security of the initialisation process. The recommendations given are based on both the results in the literature and the work in this thesis.

Abstract: In today’s digital world cryptography is used to secure information in order to provide the privacy for the intended sender and receiver by managing the message with the public key. The objective of this work is to securing the key of Playfair cipher using RSA algorithm. It is a two stage application, in first stage the existing methods of Playfair cipher modified by increasing in the size of matrix, so that the restrictions of earlier works of PF cipher using 5×5 matrix were overcome in the proposed work. The proposed method use a 12×8 matrix which contain all alphabetic, numeric and special character use in keyboard as input. This work is an enhancement to the existing algorithms that uses 5×5 matrix to pick cipher characters. It makes use of alphabets both lower and upper case characters, number and special characters for constructing the contents of the matrix. In the second stage, RSA public key encryption technique is used for sending the key of the PF ciphers securely. Finally, the security strength of the whole system has been analyzed and tried to fulfil the requirement of security.

Abstract: In this paper, based on chaotic systems and balanced Feistel network structure, a symmetric block cipher with 256-bit secret key is proposed. The cipher operates on 64-bit plaintext blocks through 16 rounds computing. Within the kernel component of the cipher, i.e., round function F, a hyperchaotic system with four-wing attractors is used to improve the complicated and unpredictability of the ciphertexts. Furthermore, a chaos-based S-Box is adopted for generating the round subkeys. The numerical simulation results and security analysis has shown that the proposed cipher possess the desirable cryptographic properties and can be used in information security field.

Abstract: Cryptography is the art of encoding messages into an unreadable form from a sender and re-transforming back to its readable form at the receiver end. This is an enhanced Caesar cipher against frequency analysis using bidirectional shift. This algorithm encrypts message bit by bit or character by character (stream cipher) and uses one key ideology (symmetric key cipher), the sender encrypts the message before transmitting and the receiver decrypts upon receiving using the same key as the one used for the encryption. It shifts the plain text characters to different direction which eliminates repetition of characters in the cipher text. Previous versions of Caesar cipher hadonly 26 English alphabets to be encrypted, which the attacker knew that there were only 26 choices to choose from, to determine the plain text. And when the alphabet of the same type are encrypted, they will have the same symbol representing each, which gives hint to attacker on how to break it by using frequency cryptanalysis. The enhanced method (Enhanced Caesar cipher) has 95 characters as digital messages as against 26 alphabets. Based on this method, the sender will transposition the bits in the message according to their sequence arrangement (odd and even position) to shift the characters in the odd position to the left and characters in the even position to the right side, based on the key given by the user, as the key to both shifts. Shifting the plain text to different directions mitigates the problem of repetition which the previous version suffers from. To make decryption more difficult, each character will switch position with the next to randomize their arrangement. The cipher was successfully developed and working accurately. It was developed on java platform using java eclipse IDE and NETBEANS IDE 7. 1. 2. It has successfully passed all the tests and proven its accuracy obtaining the result of 100% repetition free. Thus, the proposed method is highly resistant to frequency analysis. This provides more security than the earlier versions and it serves as an option to be integrated with other algorithms to strengthen the security.