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A nonce is a cryptographic input value which must never repeat within a given context. Nonces are important for the security of many cryptographic building blocks, such as stream ciphers, block cipher modes of operation, and message authentication codes. Nonetheless, the correct generation of nonces is rarely discussed in the cryptographic literature. In this paper, we collect a number of nonce generators and describe their cryptographic properties. In particular, we derive upper bounds on the nonce collision probabilities of nonces that involve a random component, and lower bounds on the resulting nonce lengths. We also discuss an important practical vulnerability of nonce-based systems, namely the nonce reset problem. While ensuring that nonces never repeat is trivial in theory, practical systems can suffer from accidental or even malicious resets which can wipe out the nonce generators current state. After describing this problem, we compare the resistance of the nonce generators described to nonce resets by again giving formal bounds on collision probabilities and nonce lengths. The main purpose of this paper is to provide a help for system designers who have to choose a suitable nonce generator for their application. Thus, we conclude by giving recommendations indicating the most suitable nonce generators for certain applications. [ABSTRACT FROM AUTHOR]

In this paper, we describe a cache-timing attack against the stream cipher HC-256, which is the strong version of eStream winner HC-128. The attack is based on an abstract model of cache timing attacks that can also be used for designing stream ciphers. From the observations made in our analysis, we derive a number of design principles for hardening ciphers against cache timing attacks. [ABSTRACT FROM AUTHOR]

Cache timing attacks are a class of side-channel attacks that is applicable against certain software implementations. They have generated significant interest when demonstrated against the Advanced Encryption Standard (AES), but have more recently also been applied against other cryptographic primitives. In this paper, we give a cache timing cryptanalysis of stream ciphers using word-based linear feedback shift registers (LFSRs), such as Snow, Sober, Turing, or Sosemanuk. Fast implementations of such ciphers use tables that can be the target for a cache timing attack. Assuming that a small number of noise-free cache timing measurements are possible, we describe a general framework showing how the LFSR state for any such cipher can be recovered using very little computational effort. For the ciphers mentioned above, we show how this knowledge can be turned into efficient cache-timing attacks against the full ciphers. [ABSTRACT FROM AUTHOR]

Entity recognition does not ask whether the message is from some entity X, just whether a message is from the same entity as a previous message. This turns turns out to be very useful for low-end devices. The current paper proposes a new protocol – the ˵Jane Doe Protocol″ –, and provides a formal proof of its concrete security. The protocol neither employs asymmetric cryptography, nor a trusted third party, nor any key pre-distribution. It is suitable for light-weight cryptographic devices such as sensor network motes and RFID tags. [ABSTRACT FROM AUTHOR]

The stream cipher Rabbit was first presented at FSE 2003 [3], and no attacks against it have been published until now. With a measured encryption/decryption speed of 3.7 clock cycles per byte on a Pentium III processor, Rabbit does also provide very high performance. This paper gives a concise description of the Rabbit design and some of the cryptanalytic results available. [ABSTRACT FROM AUTHOR]

We present Badger, a new fast and provably secure MAC based on universal hashing. In the construction, a modified tree hash that is more efficient than standard tree hashing is used and its security is proven. Furthermore, in order to derive the core hash function of the tree, we use a novel technique for reducing Δ-universal function families to universal families. The resulting MAC is very efficient on standard platforms both for short and long messages. As an example, for a 64-bit tag, it achieves performances up to 2.2 and 1.3 clock cycles per byte on a Pentium III and Pentium 4 processor, respectively. The forgery probability is at most 2-52.2. Keywords: MAC, universal hash, tree, pseudo-random generator [ABSTRACT FROM AUTHOR]

We propose a new attack on the self-shrinking generator [8]. The attack is based on a backtracking algorithm and will reconstruct the key from a short sequence of known keystream bits. We give both mathematical and empirical evidence for the effectiveness of this attack. The algorithm takes at most O(20.694L) steps, where L is the key length. Thus, our attack is more efficient than previously known key reconstruction algorithms against the self-shrinking generator that operate on short keystream sequences. [ABSTRACT FROM AUTHOR]