« Womcodes » construits à partir de géométries projectives

Nous considérons des mémoires constituées de positions permettant l'écriture irréversible d'un bit (wits) . Un wit contient initialement un zéro, qui peut être définitivement transformé en un . Nous utilisons des techniques de codag e pour réutiliser ces mémoires à écriture unique avec un rendement élevé .We consider storage media which consist of a number of write-once bit positions (wits) . A wit initially contains a "0", that may be irreversibly overwritten with a "1". It was shown by Rivest and Shamir [5] that, by coding techniques one can reuse such a write-once memor y (worn) up to a very high rate . We present two new cyclic womcodes, based on PG (2,2) and PG (3,2) respectively , which attain the RS-bound. These codes can be decoded with a decoding algorithm for Hamming codes . Some other high-rate womcodes, derived from those above, are discussed

SoK: Plausibly Deniable Storage

Data privacy is critical in instilling trust and empowering the societal pacts of modern technology-driven democracies. Unfortunately, it is under continuous attack by overreaching or outright oppressive governments, including some of the world\u27s oldest democracies. Increasingly-intrusive anti-encryption laws severely limit the ability of standard encryption to protect privacy. New defense mechanisms are needed. Plausible deniability (PD) is a powerful property, enabling users to hide the existence of sensitive information in a system under direct inspection by adversaries. Popular encrypted storage systems such as TrueCrypt and other research efforts have attempted to also provide plausible deniability. Unfortunately, these efforts have often operated under less well-defined assumptions and adversarial models. Careful analyses often uncover not only high overheads but also outright security compromise. Further, our understanding of adversaries, the underlying storage technologies, as well as the available plausible deniable solutions have evolved dramatically in the past two decades. The main goal of this work is to systematize this knowledge. It aims to: - identify key PD properties, requirements, and approaches; - present a direly-needed unified framework for evaluating security and performance; - explore the challenges arising from the critical interplay between PD and modern system layered stacks; - propose a new trace-oriented PD paradigm, able to decouple security guarantees from the underlying systems and thus ensure a higher level of flexibility and security independent of the technology stack. This work is meant also as a trusted guide for system and security practitioners around the major challenges in understanding, designing, and implementing plausible deniability into new or existing systems

Covering Radius 1985-1994

We survey important developments in the theory of covering radius during the period 1985-1994. We present lower bounds, constructions and upper bounds, the linear and nonlinear cases, density and asymptotic results, normality, specific classes of codes, covering radius and dual distance, tables, and open problems