RC4 GGHN Cryptography Algorithm for Message Security

Cryptography is a technique that is generally used in security in the process of exchanging information in the form of text messages, picture messages, or others involving two or more users. There are many types and classifications of cryptography developed to date that are able to provide security for the information sent. Modern cryptography that is popular and widely used is the Rivest Cipher (RC4) algorithm. RC4 cryptography is a type of stream cipher, which processes units or input data at one time. This research will use a combination of several message character lengths, namely 50, 100, 250, 500, 1000, 2500, 5000, 10000 characters, and tested using several key lengths, namely 5, 10, 25, 50, 100 characters. from testing with message length parameters and keys then the results will be compiled into a table and described into an image for easy understanding. Research results show it can be concluded that the length of the key used in encryption does not significantly affect the effectiveness of the system processing time. In addition, the length of the text has a big influence in determining the length of the system process in encrypting and decrypting messages. the more the number of characters that will be sent, the higher the processing time required to perform the security process once using the RC4 GGHN cryptography algorith

Distinguishing Attacks on Stream Ciphers Based on Arrays of Pseudo-random Words

In numerous modern stream ciphers, the internal state consists of a large array of pseudo-random words, and the output key-stream is a relatively simple function of the state. In [Paul-Preneel], it was heuristically shown that in various cases this structure may lead to distinguishing attacks on the cipher. In this paper we further investigate this structural attack. We present a rigorous proof of the main probabilistic claim used in the attack in the basic cases, and demonstrate by examining a concrete example (the cipher SN3) that the heuristic assumptions of the attack are remarkably precise in more complicated cases. Furthermore, we use the general technique to devise a distinguishing attack on the stream cipher MV3 requiring $2^{82}$ words of key-stream. Unlike the attacks in [Paul-Preneel], our attack does not concentrate on the least significant bits of the words, thus allowing to handle the combination of more operations (XORs, modular additions and multiplications, and rotations by a fixed number of bits) in the update and output rules of the cipher

ElsieFour: A Low-Tech Authenticated Encryption Algorithm For Human-to-Human Communication

ElsieFour (LC4) is a low-tech cipher that can be computed by hand; but unlike many historical ciphers, LC4 is designed to be hard to break. LC4 is intended for encrypted communication between humans only, and therefore it encrypts and decrypts plaintexts and ciphertexts consisting only of the English letters A through Z plus a few other characters. LC4 uses a nonce in addition to the secret key, and requires that different messages use unique nonces. LC4 performs authenticated encryption, and optional header data can be included in the authentication. This paper defines the LC4 encryption and decryption algorithms, analyzes LC4\u27s security, and describes a simple appliance for computing LC4 by hand

Cryptanalysis of symmetric key primitives

Block ciphers and stream ciphers are essential building blocks that are used to construct computing systems which have to satisfy several security objectives. Since the security of these systems depends on the security of its parts, the analysis of these symmetric key primitives has been a goal of critical importance. In this thesis we provide cryptanalytic results for some recently proposed block and stream ciphers. First, we consider two light-weight block ciphers, TREYFER and PIFEA-M. While TREYFER was designed to be very compact in order to fit into constrained environments such as smart cards and RFIDs, PIFEA-M was designed to be very fast in order to be used for the encryption of multimedia data. We provide a related-key attack on TREYFER which recovers the secret key given around 2 11 encryptions and negligible computational effort. As for PIFEA-M, we provide evidence that it does not fulfill its design goal, which was to defend from certain implementation dependant differential attacks possible on previous versions of the cipher. Next. we consider the NGG stream cipher, whose design is based on RC4 and aims to increase throughput by operating with 32-bit or 64-bit values instead of with 8-bit values. We provide a distinguishing attack on NGG which requires just one keystream word. We also show that the first few kilobytes of the keystream may leak information about the secret key which allows the cryptanalyst to recover the secret key in an efficient way. Finally, we consider GGHN, another RC4-like cipher that operates with 32-bit words. We assess different variants of GGHN-Iike algorithms with respect to weak states, in which all internal state words and output elements are even. Once GGHN is absorbed in such a weak state, the least significant bit of the plaintext words will be revealed only by looking at the ciphertext. By modelling the algorithm by a Markov chain and calculating the chain absorption time, we show that the average number of steps required by these algorithms to enter this weak state can be lower than expected at first glance and hence caution should be exercised when estimating this numbe

Towards a General RC4-Like Keystream Generator

RC4 was designed in 1987 when 8-bit and 16-bit processors were commercially available. Today, most processors use 32-bit or 64bit words but using original RC4 with 32/64 bits is infeasible due to the large memory constraints and the number of operations in the key scheduling algorithm. In this paper we propose a new 32/64-bit RC4like keystream generator. The proposed generator produces 32 or 64 bits in each iteration and can be implemented in software with reasonable memory requirements. It has a huge internal state and offers higher resistance to state recovery attacks than the original 8-bit RC4. Further, on a 32-bit processor the generator is 3.1 times faster than original RC4. We also show that it can resist attacks that are successful on the original RC4. The generator is suitable for high speed software encryption

Design of Stream Ciphers and Cryptographic Properties of Nonlinear Functions

Block and stream ciphers are widely used to protect the privacy of digital information. A variety of attacks against block and stream ciphers exist; the most recent being the algebraic attacks. These attacks reduce the cipher to a simple algebraic system which can be solved by known algebraic techniques. These attacks have been very successful against a variety of stream ciphers and major efforts (for example eSTREAM project) are underway to design and analyze new stream ciphers. These attacks have also raised some concerns about the security of popular block ciphers. In this thesis, apart from designing new stream ciphers, we focus on analyzing popular nonlinear transformations (Boolean functions and S-boxes) used in block and stream ciphers for various cryptographic properties, in particular their resistance against algebraic attacks. The main contribution of this work is the design of two new stream ciphers and a thorough analysis of the algebraic immunity of Boolean functions and S-boxes based on power mappings. First we present WG, a family of new stream ciphers designed to obtain a keystream with guaranteed randomness properties. We show how to obtain a mathematical description of a WG stream cipher for the desired randomness properties and security level, and then how to translate this description into a practical hardware design. Next we describe the design of a new RC4-like stream cipher suitable for high speed software applications. The design is compared with original RC4 stream cipher for both security and speed. The second part of this thesis closely examines the algebraic immunity of Boolean functions and S-boxes based on power mappings. We derive meaningful upper bounds on the algebraic immunity of cryptographically significant Boolean power functions and show that for large input sizes these functions have very low algebraic immunity. To analyze the algebraic immunity of S-boxes based on power mappings, we focus on calculating the bi-affine and quadratic equations they satisfy. We present two very efficient algorithms for this purpose and give new S-box constructions that guarantee zero bi-affine and quadratic equations. We also examine these S-boxes for their resistance against linear and differential attacks and provide a list of S-boxes based on power mappings that offer high resistance against linear, differential, and algebraic attacks. Finally we investigate the algebraic structure of S-boxes used in AES and DES by deriving their equivalent algebraic descriptions