Stream ciphers are still widely used to efficiently encrypt large amounts of data. Contrary to asymmetric encryption, stream ciphers are easy to implement in hardware and offer a high encryption speed. Using information theory, it is possible to proof that an arbitrary level of security can be achieved. However small flaws in the implementation of stream ciphers can lead to severe weaknesses. T...

There are two basic types of symmetric algorithms: block ciphers and stream ciphers. Block ciphers operate on blocks of plaintext and ciphertext—usually of 64 bits but sometimes longer. Stream ciphers operate on streams of plaintext and ciphertext one bit or byte (sometimes even one 32-bit word) at a time. With a block cipher, the same plaintext block will always encrypt to the same ciphertext ...

The thesis mainly reviews the mathematical analysis of the security of stream ciphers. Firstly, we will introduce the background of stream ciphers with their design principles and theoretical security from the information theory viewpoint. Then we will introduce the algebraic tools for the analysis of linear recurring sequences followed by discussions on the two kinds of basic nonlinear filters...

The profile 1 submissions to the eSTREAM call for stream ciphers aim at achieving a high throughput in software. But, for the embedded systems, the trade-off between the throughput and the code size is more critical. We here study the ROM footprints of several eSTREAM stream ciphers on an ARM920T processor. Most notably we propose some modifications in the implementations of several ciphers whi...

Vaidyanathan suggested the use of filter banks with coefficients in finite fields as stream ciphers. We show how to break those ciphers. A more general class of ciphers is introduced, which includes many well-known block ciphers, like DES, IDEA, etc. These ciphers are derived from filter banks over group rings.

Hermes8 [6,7] is one of the stream ciphers submitted to the ECRYPT Stream Cipher Project (eSTREAM [3]). In this paper we present an analysis of the Hermes8 stream ciphers. In particular, we show an attack on the latest version of the cipher (Hermes8F), which requires very few known keystream bytes and recovers the cipher secret key in less than a second on a normal PC. Furthermore, we make some...

eSTREAM called for new stream ciphers designed for niche areas such as exceptional performance in software and hardware where resources are restricted. This project provides an open platform to discuss these ciphers. Trivium is one of the promising new ciphers submitted to it. Until now, no attack has been successfully applied to it. This paper illustrates new design principles of stream cipher...

We propose and analyze the Lizard-construction, a way to construct keystream generator (KSG) based stream ciphers with provable 2 3 n-security with respect to generic time-memory-data tradeoff attacks. Note that for the vast majority of known practical KSG-based stream ciphers such attacks reduce the effective key length to the birthday bound n/2, where n denotes the inner state length of the u...

Chaotic cryptology is widely investigated recently. This paper reviews the progress in this area and points out some existent problems in digital chaotic ciphers. As a comprehensive solution to these problems, a novel pseudo-random bit generator based on a couple of chaotic systems called CCS-PRBG is presented. Detailed theoretical analyses show that it has perfect cryptographic properties, and...

Stream ciphers are encryption algorithms used for ensuring the privacy of digital telecommunications. They have been widely used for encrypting military communications, satellite communications, pay TV encryption and for voice encryption of both fixed lined and wireless networks. The current multi year European project eSTREAM, which aims to select stream ciphers suitable for widespread adoptat...