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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

ATPG based Preimage Computation: Efficient Search Space Pruning using ZBDD

Chandrasekar, Kameshwar 06 August 2003 (has links)
Preimage Computation is a fundamental step in Formal Verification of VLSI designs. Conventional OBDD-based methods for Formal Verification suffer from spatial explosion, since large designs can blow up in terms of memory. On the other hand, SAT/ATPG based methods are less demanding on memory. But the run-time can be huge for these methods, since they must explore an exponential search space. In order to reduce this temporal explosion of SAT/ATPG based methods, efficient learning techniques are needed. Conventional ATPG aims at computing a single solution for its objective. In preimage computation, we must enumerate all solutions for the target state during the search. Similar sub-problems often occur during preimage computation that can be identified by the internal state of the circuit. Therefore, it is highly desirable to learn from these search-states and avoid repeated search of identical solution/conflict subspaces, for better performance. In this thesis, we present a new ZBDD based method to compactly store and efficiently search previously explored search-states. We learn from these search-states and avoid repeating subsets and supersets of previously encountered search spaces. Both solution and conflict subspaces are pruned based on simple set operations using ZBDDs. We integrate our techniques into a PODEM based ATPG engine and demonstrate their efficiency on ISCAS '89 benchmark circuits. Experimental results show that upto 90% of the search-space is pruned due to the proposed techniques and we are able to compute preimages for target states where a state-of-the-art technique fails. / Master of Science
2

Transition Fault-Driven Delay Defect Diagnosis in the Presence of Process Variations

Toulas, Theodoros 01 December 2015 (has links)
It is shown that the path delay fault (PDF) model may not be very effective in guiding post silicon debug. It is also shown that the multiple transition fault (MTF) model allows for significant reduction of the initial suspect set. However the number of faults is much higher than the number of PDFs. A Monte Carlo approach is presented that uses multiple transition faults with appropriately assigned weights to identify defective embedded segments. It is experimentally verified that the approach guides diagnosis more efficiently than the path delay fault model. Fault-implicit algorithms are presented to cope with fault-related scalability challenges. Our results in ISCAS '89, ISCAS'85, ITC '99 benchmarks show a huge reduction in the suspect set using the proposed fault model and algorithms. It is shown that the proposed method guides effectively fault diagnosis.
3

Protection des contenus des images médicales par camouflage d'informations secrètes pour l'aide à la télémédecine / Medical image content protection by secret information hiding to support telemedicine

Al-Shaikh, Mu'ath 22 April 2016 (has links)
La protection de l’image médicale numérique comporte au moins deux aspects principaux: la sécurité et l’authenticité. Afin d’assurer la sécurité, l’information doit être protégée vis-à-vis des utilisateurs non autorisés. L’authenticité permet quant à elle de s’assurer que la donnée reçue n’est pas modifiée, n’est pas altérée, et qu’elle est bien envoyée par l’expéditeur supposé. La « technique » cryptographique garantit la sécurité en faisant l’hypothèse que l’expéditeur et le destinataire ont des clés permettant respectivement de crypter et de décrypter le message. De cette manière, seule la personne possédant la bonne clé peut décrypter le message et accéder au contenu de la donnée médicale. Dans cette thèse, nous avons apporté plusieurs contributions. La principale contribution est la proposition de solutions de tatouage d'images médicales robustes et réversibles dans le domaine spatial basées respectivement sur l’analyse de concepts formels (FCA) et le diagramme de décision binaire par suppression des zéros (ZBDD). La seconde est une approche de tatouage d’image médicale semi-aveugle pour la détection de modifications malveillantes. Une autre contribution est la proposition d'un système de chiffrement symétrique sécurisé basé sur les N-grams. La dernière contribution est un système hybride de tatouage et de cryptographie d’image médicale qui s’appuie sur une nouvelle forme de carte chaotique (chaotic map) pour générer des clés ayant des propriétés spécifiques, et qui permet d'obtenir une meilleure efficacité, une grande robustesse et une faible complexité par rapport aux approches existantes. / The protection of digital medical image comprises at least two main aspects: security and authentication. In order to ensure the security, the information has to be protected from the unauthorized users while the authentication confirms that the received data is not affected or modified and is sent by the intended sender (watermarking). The cryptography technique proves the security issues by assuming the intended sender and intended receiver have some security aspects called keys. So, after encryption of the digital material from the sender side, the person who has the key (receiver) can decrypt and access the content of the digital material. In this thesis, we have brought several contributions. The main one is the provision of robust and reversible medical image watermarking solutions in the spatial domain based respectively on FCA and ZBDD. The second one is a semi-blind medical image watermarking approach for the tamper detection. Another contribution is the proposal of a secure symmetric encryption system based on N-gram. The last contribution is a hybrid watermarking and cryptography medical image system which focuses on a new form of chaotic map to generate keys with specific properties, and achieves better efficiency, high robustness and low complexity than the existing approaches.

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