Bit

Résumé

Le bit est l'unité la plus simple dans un système de numération, ne pouvant prendre que deux valeurs, désignées le plus souvent par les chiffres 0 et 1. Un bit peut représenter aussi bien une alternative logique, exprimée par faux et vrai, qu'un « chiffre binaire », binary digit en anglais, dont le mot bit, qui signifie « morceau », est aussi l'abréviation. Dans la théorie de l'information, un bit est la quantité minimale d'information transmise par un message, et constitue à ce titre l'unité de mesure de base de l'information en informatique. La quantité d'information effectivement transmise s'exprime en shannons, et ne peut dépasser la taille du message en bits. Les systèmes numériques traitent exclusivement des informations réduites en bits, en général associés dans des groupes de taille fixe appelés bytes (/bait/). Usages Le mot « bit » est la contraction des mots anglais binary digit, qui signifient « chiffre binaire », avec un jeu de mots sur bit, « petit morceau

Source officielle

https://fr.wikipedia.org/wiki/Bit

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Cours associés (90)

Students extend their knowledge on wireless communication systems to spread-spectrum communication and to multi-antenna systems. They also learn about the basic information theoretic concepts, about channel coding, and bit-interleaved coded modulation.

L'objectif de ce cours est d'introduire les étudiants à la pensée algorithmique, de les familiariser avec les fondamentaux de l'Informatique et de développer une première compétence en programmation (langage C++).

IC Design II presents the fundamentals of digital integrated circuit design. The methods and techniques aiming at the fabrication and development of digital integrated circuits are reviewed, the major design style pertaining to digital logic and memory are presented.

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Séances de cours associées (198)

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This thesis presents, firstly, an introduction to the current state of the art in isogeny-based cryptography, and secondly, a side-channel differential power analysis of SIKE—an isogeny-based key exchange algorithm—in semi-static mode. These attacks have been realized on an ARM implementation of SIKEp434 in the pqm4 library which is itself based on the reference implementation of the SIKE submission to the NIST post-quantum standardization process. We have analyzed the power consumption of an STM32F3 board which features an ARM Cortex-M4 microcontroller through Pearson’s correlation in the Hamming Weight model. We investigated an information leak of the 3-points Ladder involved in the decapsulation mechanism of SIKEp434. As this function was used to compute P + [m]Q where m is Bob’s private key and P, Q are two public points on a known elliptic curve, we showed that we can recover every bit of Bob’s private key by exploiting the power consumption as a bit distinguisher through a correlation with the result of an ADDS assembly instruction. A proof of leakage of the ADDS instruction of ARM has been demonstrated in this thesis. Ideas for countermeasures to prevent this attack are discussed.

2020

Chargement

Electric Field Effects in the Skyrmion Lattice Hosting Magnet Cu2OSeO3

Saumya Shivam

Magnetic skyrmions have garnered much attention in recent years because of their non trivial topology and potential to be used in next generation memory devices. They may exist individually or as a lattice of skyrmions(SkL). A number of investigations have been done on SkL in metallic samples, but recently a few magnetoelectric insulators have also begun to attract a lot of attention. The magnetoelectric nature of these materials presents a possibility to make prototype memory devices where skyrmions form a storage bit and can be controlled with only electric fields without the losses caused by Joule heating. We focus here on the material Cu2OSeO3, for which interesting electric field effects have been seen like the control of size of the region in the phase diagram where SkL is stable, creation of metastable skyrmions and the use of magnetolectric susceptibility to map the phase diagram. We use the magnetoelectric susceptibility to explore the above mentioned effects of electric fields, attempting to confirm previous reports of such effects using different techniques like neutron scattering and AC susceptibility. We also propose a new design to create metastable SkL state at low temperatures and confirm its existence using magnetoelectric susceptibility. We also attempt to measure the change in polarization between the SkL phase and the trivial phase on application of DC electric fields, which in principle could lead to electrical readout of skyrmions in a prototype skyrmion based memory device.

2018

Chargement

Motivated by concerns for user privacy, we design a steganographic system ("stegosystem") that enables two users to exchange encrypted messages without an adversary detecting that such an exchange is taking place. We propose a new linguistic stegosystem based on a Long Short-Term Memory (LSTM) neural network. We demonstrate our approach on the Twitter and Enron email datasets and show that it yields high-quality steganographic text while significantly improving capacity (encrypted bits per word) relative to the state-of-the-art.

2017

Chargement