• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 5
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 10
  • 7
  • 6
  • 5
  • 5
  • 4
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • 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

The effects of asphalt binder oxidation on hot mix asphalt concrete mixture rheology and fatigue performance

Jung, Sung Hoon 02 June 2009 (has links)
Asphalt oxidation causes major changes to binder properties and is hypothesized to be a major contributor to age-related pavement failure such as fatigue cracking. Extensive laboratory aging research has been done to assess the effects of oxidation on binder properties. Previous work shows binder oxidation makes the binder stiffer and more brittle, leading to higher binder stresses under a given deformation. Failure occurs when these stresses exceed the strength of the binder. However, binder oxidation in pavements has not been studied in the same detail as laboratory aging of neat binders. The impact of binder oxidation on long-term pavement performance has been either underestimated or ignored. This research includes studies of binder oxidation in Texas pavements to compare the field aging with laboratory neat binder aging, the impact of binder oxidation on HMAC mixture aging and HMAC mixture fatigue performance, and fundamental rheological property changes of the binder and the mixture. Binder oxidation is studied in fifteen pavements from locations across Texas. Results indicate that unmodified binders in pavements typically oxidize and harden to a degree that exceeds generally accepted pavement aging assumptions. This hardening may also extend much deeper into the pavement than has been previously assumed or documented. Data suggest that pavements can oxidize at rates surprisingly uniform with depth once early oxidation occurs, and that these rates continue for an extended time. Laboratory-aged HMAC mixtures and binders were tested and analyzed for fatigue resistance and their rheological properties. Mixture aging shows the same aging mechanisms as neat binder aging. Both binder and mixture have a higher modulus with aging and a good rheological correlation. The decline in mixture fatigue life (determined using the calibrated mechanistic fatigue analysis approach with surface energy measurement) due to oxidation is significant. Pavement service life is dependent on the mixture, but can be estimated by a cumulative damage approach that considers binder oxidation and pavement loading rate simultaneously. The differences in expected pavement life arise from differences in the rate of binder stiffening due to oxidation and the impact of this stiffening on the decline of fatigue life.
2

Message Authentication Codes On Ultra-Low SWaP Devices

Liao, Che-Hsien 27 May 2022 (has links)
This thesis focuses on specific crypto algorithms, Message Authentication Codes (MACs), running on ultra-low SWaP devices. The type of MACs we used is hash-based message authentication codes (HMAC) and cipher-block-chaining message authentication code (CBC-MAC). The most important thing about ultra-low SWaP devices is their energy usage. This thesis measures different implementations' execution times on ultra-low SWaP devices. We could understand which implementation is suitable for a specific device. In order to understand the crypto algorithm we used, this thesis briefly introduces the concept of hash-based message authentication codes (HMAC) and cipher-block-chaining message authentication code (CBC-MAC) from a high level, including their usage and advantage. The research method is empirical research. This thesis determines the execution times of different implementations. These two algorithms (HMAC and CBC-MAC) contain three implementations. The result comes from those implementations running on the devices we used. / Master of Science / The deployments of 5G cellular networks are now onboard. The demand increased due to consumers and the availability of more affordable devices. The amount of investment in 5G technology and infrastructure increases market interest in IoT. The 5G network security is essential. How to secure user privacy and their sensitive data while they use 5g network has become a big issue and needs to be solved. However, not all popular crypto algorithms are suited to all devices, especially in those resource-limited microcontrollers. In this thesis, we will deal with Message Authentication Codes that provide the data integrity check. With resource limit devices, energy usage is an important issue. We will identify which implementations have better energy usage depending on the device features. This thesis will use three implementations for each algorithm. The result of our experiment provide a straightforward way that helps people understand which implementation can run more efficiently on specific ultra-low devices.
3

Κώδικες πιστοποίησης μηνυμάτων : σχεδιασμός και υλοποιήσεις σε πλατφόρμες υλικού και συγκριτικές αποτιμήσεις / Message authentication codes : designs and implementations in hardware platforms and comparisons

Χαράλαμπος, Μιχαήλ 16 June 2011 (has links)
Σε αυτή τη μεταπτυχιακή διπλωματική εργασία μελετήθηκαν, αναπτύχτηκαν και συγκριθήκαν αρχιτεκτονικές για κρυπτογραφικές εφαρμογές που χρησιμοποιούνται στης τεχνικές πιστοποίησης μηνυμάτων. Σε αυτές χρησιμοποιήθηκαν και τεχνικές βελτιστοποίησης της απόδοσης. Στην ασφάλεια μετάδοσης των πληροφοριών, η πιστοποίηση μηνύματος είναι μία θεμελιώδης τεχνική, η οποία χρησιμοποιείται για να επιβεβαιώσει ότι τα ληφθέντα μηνύματα προέρχονται από τον σωστό αποστολέα και ότι δεν έχουν τροποποιηθεί κατά τη μετάδοση. Στην πιστοποίηση μηνύματος, απαιτείται η χρήση ενός κώδικα πιστοποίησης μηνύματος (Message Authentication Code-MAC). Οι τεχνικές για να δημιουργηθεί ένα MAC γίνεται με δύο τρόπους: α)Με χρήση μίας hash συνάρτησης σε συνδυασμό με ένα μυστικό κλειδί και αναφέρεται σαν HMAC (Hash-based MAC). β)Με χρήση ενός block cipher αλγορίθμου κρυπτογράφησης σε συνδυασμό με ένα μυστικό κλειδί και αναφέρεται σαν CMAC (Cipher block-based MAC). Θα υλοποιηθούν οι δύο παραπάνω τρόποι-μέθοδοι παραγωγής MAC, σε πλατφόρμες υλικού με γνώμονα την αύξηση της ρυθμαπόδοσης τους. Θα αποτιμηθεί ο ρόλος τους στα κρυπτογραφικά συστήματα ασφαλείας και σε ποιές περιπτώσεις συνίσταται η χρήση της κάθε μίας τεχνικής. Έτσι θα ξεκαθαριστούν οι διαφορές τους και θα καθοριστεί το προφίλ των εφαρμογών στης οποίες κάθε μια εκ των δύο αυτών τεχνικών ταιριάζει καλύτερα. Οι υλοποιήσεις συγκριθήκαν στην ίδια πλατφόρμα υλικού που χρησιμοποιήθηκε για την τελική υλοποίηση ώστε σε κάθε περίπτωση, ανάλογα με της απαιτήσεις της εκάστοτε εφαρμογής, να βρεθεί και η βέλτιστη λύση από πλευράς κόστους. / In the present M.Sc. thesis, several architectures for message authentication codes were studied, developed and compared to each other. Performance optimization techniques were exploited as well. Message Authentication Codes (MACs) are widely used in order to protect both a message's integrity -by ensuring that a different MAC will be produced if the message has changed - as well as its authenticity (only someone who knows the secret key could have generated a valid MAC). A message authentication code is an authentication tag (also called a checksum) derived by applying an authentication scheme, together with a secret key, to a message. Typically MACs are produced through: α) HMAC mechanism which is based on a FIPS approved collision-resistant hash function in combination with a secret key (Hash-based MAC). β)CMAC mechanism which is based on a block cipher algorithm in combination with a secret key (Cipher block-based MAC). The above two ways (mechanisms) for producing MACs were designed and implemented in hardware taking into consideration the increase of their throughput. The cryptographic systems in which the above two are exploited were described. Their key role in these systems was valued through an investigation concerning the way of their incorporation. Thus, the differences between them were clarified determining the applications where each one is better befitted. HMAC and CMAC designs are implemented in the same hardware FPGA platform and compared to each other in terms of operating frequency, area consumption and throughput. In this way, the best solution between them concerning their overall cost can be designated.
4

Securing the Future of 5G Smart Dust: Optimizing Cryptographic Algorithms for Ultra-Low SWaP Energy-Harvesting Devices

Ryu, Zeezoo 12 July 2023 (has links)
While 5G energy harvesting makes 5G smart dust possible, stretching computation across power cycles affects cryptographic algorithms. This effect may lead to new security issues that make the system vulnerable to adversary attacks. Therefore, security measures are needed to protect data at rest and in transit across the network. In this paper, we identify the security requirements of existing 5G networks and the best-of-breed cryptographic algorithms for ultra-low SWaP devices in an energy harvesting context. To do this, we quantify the performance vs. energy tradespace, investigate the device features that impact the tradespace the most, and assess the security impact when the attacker has access to intermediate results. Our open-source energy-harvesting-tolerant versions of the cryptographic algorithms provide algorithm and device recommendations and ultra-low SWaP energy-harvesting-device-optimized versions of the cryptographic algorithms. / Master of Science / Smart dust is a network of tiny and energy-efficient devices that can gather data from the environment using various sensors, such as temperature, pressure, and humidity sensors. These devices are extremely small, often as small as a grain of sand or smaller, and have numerous applications, including environmental monitoring, structural health monitoring, and military surveillance. One of the main challenges of smart dust is its small size and limited energy resources, making it challenging to power and process the collected data. However, advancements in energy harvesting and low-power computing are being developed to overcome these challenges. In the case of 5G, energy harvesting technologies can be used to power small sensors and devices that are part of the 5G network, such as the Internet of Things (IoT) devices. Examples of IoT devices are wearable fitness trackers, smart thermostats, security cameras, home automation systems, and industrial sensors. Since 5G energy harvesting impacts the daily lives of people using the relevant devices, our research seeks to find out what kind of measures are necessary to guarantee their security.
5

HASH STAMP MARKING SCHEME FOR PACKET TRACEBACK

NEIMAN, ADAM M. January 2005 (has links)
No description available.
6

Fault Tolerant Cryptographic Primitives for Space Applications

Juliato, Marcio January 2011 (has links)
Spacecrafts are extensively used by public and private sectors to support a variety of services. Considering the cost and the strategic importance of these spacecrafts, there has been an increasing demand to utilize strong cryptographic primitives to assure their security. Moreover, it is of utmost importance to consider fault tolerance in their designs due to the harsh environment found in space, while keeping low area and power consumption. The problem of recovering spacecrafts from failures or attacks, and bringing them back to an operational and safe state is crucial for reliability. Despite the recent interest in incorporating on-board security, there is limited research in this area. This research proposes a trusted hardware module approach for recovering the spacecrafts subsystems and their cryptographic capabilities after an attack or a major failure has happened. The proposed fault tolerant trusted modules are capable of performing platform restoration as well as recovering the cryptographic capabilities of the spacecraft. This research also proposes efficient fault tolerant architectures for the secure hash (SHA-2) and message authentication code (HMAC) algorithms. The proposed architectures are the first in the literature to detect and correct errors by using Hamming codes to protect the main registers. Furthermore, a quantitative analysis of the probability of failure of the proposed fault tolerance mechanisms is introduced. Based upon an extensive set of experimental results along with probability of failure analysis, it was possible to show that the proposed fault tolerant scheme based on information redundancy leads to a better implementation and provides better SEU resistance than the traditional Triple Modular Redundancy (TMR). The fault tolerant cryptographic primitives introduced in this research are of crucial importance for the implementation of on-board security in spacecrafts.
7

Fault Tolerant Cryptographic Primitives for Space Applications

Juliato, Marcio January 2011 (has links)
Spacecrafts are extensively used by public and private sectors to support a variety of services. Considering the cost and the strategic importance of these spacecrafts, there has been an increasing demand to utilize strong cryptographic primitives to assure their security. Moreover, it is of utmost importance to consider fault tolerance in their designs due to the harsh environment found in space, while keeping low area and power consumption. The problem of recovering spacecrafts from failures or attacks, and bringing them back to an operational and safe state is crucial for reliability. Despite the recent interest in incorporating on-board security, there is limited research in this area. This research proposes a trusted hardware module approach for recovering the spacecrafts subsystems and their cryptographic capabilities after an attack or a major failure has happened. The proposed fault tolerant trusted modules are capable of performing platform restoration as well as recovering the cryptographic capabilities of the spacecraft. This research also proposes efficient fault tolerant architectures for the secure hash (SHA-2) and message authentication code (HMAC) algorithms. The proposed architectures are the first in the literature to detect and correct errors by using Hamming codes to protect the main registers. Furthermore, a quantitative analysis of the probability of failure of the proposed fault tolerance mechanisms is introduced. Based upon an extensive set of experimental results along with probability of failure analysis, it was possible to show that the proposed fault tolerant scheme based on information redundancy leads to a better implementation and provides better SEU resistance than the traditional Triple Modular Redundancy (TMR). The fault tolerant cryptographic primitives introduced in this research are of crucial importance for the implementation of on-board security in spacecrafts.
8

Cryptographic hash functions : cryptanalysis, design and applications

Gauravaram, Praveen Srinivasa January 2007 (has links)
Cryptographic hash functions are an important tool in cryptography to achieve certain security goals such as authenticity, digital signatures, digital time stamping, and entity authentication. They are also strongly related to other important cryptographic tools such as block ciphers and pseudorandom functions. The standard and widely used hash functions such as MD5 and SHA-1 follow the design principle of Merkle-Damgard iterated hash function construction which was presented independently by Ivan Damgard and Ralph Merkle at Crypto'89. It has been established that neither these hash functions nor the Merkle-Damgard construction itself meet certain security requirements. This thesis aims to study the attacks on this popular construction and propose schemes that offer more resistance against these attacks as well as investigating alternative approaches to the Merkle-Damgard style of designing hash functions. This thesis aims at analysing the security of the standard hash function Cellular Authentication and Voice Encryption Algorithm (CAVE) used for authentication and key-derivation in the second generation (2G) North American IS-41 mobile phone system. In addition, this thesis studies the analysis issues of message authentication codes (MACs) designed using hash functions. With the aim to propose some efficient and secure MAC schemes based on hash functions. This thesis works on three aspects of hash functions: design, cryptanalysis and applications with the following significant contributions: * Proposes a family of variants to the Damgard-Merkle construction called 3CG for better protection against specific and generic attacks. Analysis of the linear variant of 3CG called 3C is presented including its resistance to some of the known attacks on hash functions. * Improves the known cryptanalytical techniques to attack 3C and some other similar designs including a linear variant of GOST, a Russian standard hash function. * Proposes a completely novel approach called Iterated Halving, alternative to the standard block iterated hash function construction. * Analyses provably secure HMAC and NMAC message authentication codes (MACs) based on weaker assumptions than stated in their proofs of security. Proposes an efficient variant for NMAC called NMAC-1 to authenticate short messages. Proposes a variant for NMAC called M-NMAC which offers better protection against the complete key-recovery attacks than NMAC. As well it is shown that M-NMAC with hash functions also resists side-channel attacks against which HMAC and NMAC are vulnerable. Proposes a new MAC scheme called O-NMAC based on hash functions using just one secret key. * Improves the open cryptanalysis of the CAVE algorithm. * Analyses the security and legal implications of the latest collision attacks on the widely used MD5 and SHA-1 hash functions.
9

Etude du potentiel d'emploi des bitumes naturels dans la production des liants bitumineux durs et des enrobés à module élevé / The potential of natural bitumens in the production of hard bituminous binder and of high modulus asphalt concretes

Themeli, Andrea 03 July 2015 (has links)
Le but de ce travail est d’étudier le potentiel d’un bitume naturel (BN) extrait en Albanie pour la production des bitumes durs (BD) et des enrobés à module élevé (EME). Pour la production des BD, différentes techniques de raffinage du pétrole existent. Néanmoins, avec certains bruts pétroliers il est impossible de les fabriquer. De plus, les BD de raffinerie comportent souvent des défauts qui limitent leurs applications. Ces raisons, couplées à des questions d’approvisionnement, conduisent à chercher des méthodes de substitution. Dans ce contexte, il est intéressant d’utiliser des BN. Cette étude a montré que le BN d’Albanie donne des BD et des EME en conformité avec la Normalisation Européenne, résistants au vieillissement et performants aux basses températures. Un dosage adéquat permet de formuler des matériaux d’une dureté désirée en réponse des exigences techniques des applications routières visées tout en facilitant la gestion des stocks de bitumes dans les centrales d’enrobages. / The aim of this thesis is to study the potential of a natural bitumen (NB) mined in Albania in the production of hard bitumens (HB) and that of high modulus asphalt concrete (HMAC). Various petroleum refining techniques are available for the production of HB. Nevertheless, this is impossible with some crude oils. In addition, HB from refineries often present shortcomings which limit their applications. These reasons, coupled with practical issues related to HB supply, motivate the research of alternative methods. In this industrial context it is interesting to use NB. This study has shown that the Albanian NB provides HB and HMAC in accordance with European Standards, resistant to aging and relatively performant at low temperatures. The proper dosage of this NB allows the formulation of materials of desired properties, in response to the technical requirements of the considered road applications, facilitating in this way the use of bitumen stocks in asphalt concrete production plants.
10

Odposlech moderních šifrovaných protokolů / Interception of Modern Encrypted Protocols

Marček, Ján January 2012 (has links)
This thesis deals with the introduction to the security mechanism.The procedure explains the basic concepts, principles of cryptography and security of modern protocols and basic principles that are used for information transmission network. The work also describes the most common types of attacks targeting the eavesdropping of communication. The result is a design of the eavesdropping and the implementation of an attack on the secure communication of the SSL protocol..The attacker uses a false certificate and attacks based on poisoning the ARP and DNS tables for this purpose. The thesis discusses the principles of the SSL protocol and methodology of attacks on the ARP and DNS tables.

Page generated in 0.0279 seconds