This thesis is focused on a relatively new branch of computer security called Cryptovirology. It uses cryptography and its principles in conjunction with designing and writing malicious codes (e.g. computer viruses, trojan horses, worms). Techniques such as viral propagation through computer networks, capabilities of current viruses and similar threats are described. Beside cryptography and computer viruses, design of the cryptovirus and methods of a cryptoviral extortion attack along with their related potential are also analyzed below in this paper. As a proof of the concept in the given area of cryptovirology, a demonstrational computer program was written. The program was implemented with the respect to the satisfaction of the essentials set to the cryptovirus.

Security protocols are used for establishing secure communication over insecure network. This document gives a brief introduction into description and formal specification in the area of security protocols design. It also includes description of the aplication library, its functions and methods how to use it.

This document describes methods of user authentication and authorisation via a trusted server. There is analysis of the system Kerberos, which is used as an inspiration for desing of a new authentication scheme. There are analysed programming layers and interfaces for specific applications ensuring user authentication and authorisation. The document contains a design and detailed description of a new authentication scheme. This scheme is implemented into the communication between email client and imap server.

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Following circumstances such as mergers and acquisitions, the IT systemsassociated with the participating organisations may need to share access towardsservices and systems with eachother. Access towards systems and services is oftencontrolled using secret information such as passwords or keys. This implies thatsharing access between IT systems is achieved by sharing secret information. This thesis proposes new methods for automatic synchronization of secretsbetween different secret management systems that may not be natively compatiblewith one another. After examining how the already existing secret managementsystems function as well as created a data centric threat model, a system design wasproposed. A secret proxy connects to each secret management system which in turnconnects to a central secret distributor that handles and updates the other proxies. The results indicate that such a system can be implemented and securely distributesecrets automatically. By synchronizing secrets automatically, the work involvedwith supporting several secret management systems in parallel which all needaccess to some common secrets could be reduced. / Under omständigheter så som sammanslagning av organisationer kan ett flertalseparata IT-system tilhörande de olika organisationerna behöva dela åtkomst mottjänster med varandra. Åtkomst mot tjänster regleras ofta med hjälp av hemliginformation så som lösenord eller nycklar. Detta innebär att delning av åtkomstmellan IT-system uppnås genom delning av hemlig information mellan dessasystem. Detta arbetet föreslår nya metoder för att automatiskt synkronisera lösenord ochhemligheter mellan flera hemlighetshanteringssystem som normalt sett inte ärkompatibla med varandra. En arkitekturell modell togs fram efter att en utvärdering av redan existerandehemlighetshanteringssystems funktionalitet samt en analys av den framtagna hotmodellengjorts. En proxy ansluter till det lokala hemlighets-hanteringssystemetsom i sin tur ansluts till ett centralt distribueringssystem vars jobb är att hanteraoch uppdatera alla proxys. Resultatet påvisar att ett system för att automatiskt synkronisera hemligheter påett säkert sätt går att bygga både i teorin och i praktiken. Automatisk synkroniseringkan minska det arbete som krävs för att hantera flera parallella system däralla behöver ha tillgång till gemensamma hemligheter.

Ensuring trustworthiness through mobile nodes is a serious issue. Indeed, securing the routing protocols in Mobile Ad Hoc Network (MANET) is of paramount importance. A key exchange cryptography technique is one such protocol. Trust relationship between mobile nodes is essential. Without it, security will be further threatened. The absence of infrastructure and a dynamic topology changing reduce the performance of security and trust in mobile networks. Current proposed security solutions cannot cope with eavesdroppers and misbehaving mobile nodes. Practically, designing a key exchange cryptography system is very challenging. Some key exchanges have been proposed which cause decrease in power, memory and bandwidth and increase in computational processing for each mobile node in the network consequently leading to a high overhead. Some of the trust models have been investigated to calculate the level of trust based on recommendations or reputations. These might be the cause of internal malicious attacks. Our contribution is to provide trustworthy communications among the mobile nodes in the network in order to discourage untrustworthy mobile nodes from participating in the network to gain services. As a result, we have presented an Elliptic Curve Diffie-Hellman key exchange and trust framework mechanism for securing the communication between mobile nodes. Since our proposed model uses a small key and less calculation, it leads to a reduction in memory and bandwidth without compromising on security level. Another advantage of the trust framework model is to detect and eliminate any kind of distrust route that contain any malicious node or suspects its behavior.

An audit log enables us to discover malfeasance in a system and to understand a security breach after it has happened. An audit log is meant to preserve information about important events in a system in a non-repudiable manner. Naturally, the audit log is often a target for malicious actors trying to cover the traces of an attack. The most common type of attack would be to try to remove or modify entries which contain information about some events in the system that a malicious actor does not want anyone to know about. In this thesis, the state-of-the-art research on secure logging is presented together with a design for a new logging system. The new design has superior properties in terms of both security and functionality compared to the current EJBCA implementation. The design is based on a combination of two well-cited logging schemes presented in the literature. Our design is an audit log built on a Merkle tree structure which enables efficient integrity proofs, flexible auditing schemes, efficient queries and exporting capabilities. On top of the Merkle tree structue, an FssAgg (Forward secure sequential Aggregate) MAC (Message Authentication Code) is introduced which strengthens the resistance to truncation-attacks and provides more options for auditing schemes. A proof-of-concept implementation was created and performance was measured to show that the combination of the Merkle tree log and the FssAgg MAC does not significantly reduce the performance compared to the individual schemes, while offering better security. The logging system design and the proof-of-concept implementation presented in this project will serve as a starting point for PrimeKey when developing a new audit log for EJBCA. / En granskningslogg är viktig eftersom den ger oss möjligheten att upptäcka misstänkt aktivitet i ett system. Granskningsloggen ger också möjligheten att undersöka och förstå ett säkerhetsintrång efter att det har inträffat. En attackerare som komprometterar ett system har ofta granskningsloggen som mål, eftersom de ofta vill dölja sina spår. I denna rapport presenteras en litteraturstudie av nuvarande forskning på säkra loggingsystem samt en design av ett nytt loggingsystem. Det nya loggingsystemet har bättre säkerhetsegentskaper och funktionalitet jämfört med den nuvarande implementationen i EJBCA. Designen bygger på en kombination av två välciterade forskningsartiklar. Vår design är en granskningslogg baserad på en Merkle träd-struktur som möjliggör effektiva bevis av loggens integritet, flexibel granskning, effektiv sökning och exportfunktionalitet. Förutom Merkle träd-strukturen består den nya loggen även av en FssAgg (Forward secure sequential Aggregate) MAC (Message Authentication Code) som förstärker loggens motstånd mot trunkeringsattacker och möjliggör fler sätt att granska loggen. En prototypimplementation skapades och prestandamätningar genomfördes som visar att kombinationen av Merkle träd-loggen och FssAgg MAC:en inte försämrar loggens prestanda jämfört med de individuella logglösningarna, trots att starkare säkerhet uppnås. Designen av det nya loggingsystemet samt prototypimplementationen kommer att utgöra en grund för PrimeKeys arbete med att implementera en ny audit log i EJBCA.

Advanced enough quantum computers promise to revolutionise fields such as cryptography, drug discovery and simulations of complex systems. Quantum computers are built on qubits which are fragile and susceptible to error-inducing interference, which is called noise. The aim of this study was to examine the effects of varying levels of noise interference on the success rate and runtimes of a quantum computer circuit design built to implement Shor’s quantum factorisation algorithm. This was conducted using the Qiskit framework for quantum computer simulation and custom noise model creation. Our results show a correlation between the level of noise interference on a circuit and the probability of getting the correct measurement. We also found a greater impact of readout errors on the success rates, one-qubit depolarising errors on runtimes and that two-qubit depolarising errors greatly affected both, which was also discussed in the study. Our findings are in line with previous research and help to highlight the importance of minimising errors on critical quantum logic gates in an algorithm. / Tillräckligt avancerade kvantdatorer lovar att revolutionera områden så som kryptografi, utveckling av nya läkemedel och simulering av komplexa system. Kvantdatorer är uppbyggda av qubits vilka är ömtåliga och mottagliga mot felinducerande interferens, vilket kallas brus. Målet med denna studie var att utforska effekten av varierande brusnivåers interferens på lyckade försök samt körtiden av en kvantdatorkrets designad för att implementera Shors algoritm. Detta gjordes med Qiskits ramverk för kvantdatorsimulering och anpassningsbara brusmodeller. Våra resultat visar en korrelation mellan nivån av brusinterferens på en krets och sannolikheten av att få den korrekt mätningen. Vi fann även en större påverkan av avläsningsfel på kvoten lyckade försök, en-qubit depolariserande fel på körtid och att två-qubit depolariserande fel hade en stor påverkan på båda, vilket vi även diskuterat i studien. Våra resultat är i linje med tidigare studier och hjälper till att lyfta fram vikten av att minimera inducerade fel på kritiska logiska grindar i en kvantdatoralgoritm.

Internet of Things (IoT) refers to a network of global and interrelated computing devices that connects humans and machines. It connects anything that has access to the internet and creates an avenue for data and information exchange. Devices within the IoT environment are embedded with processors, sensors and communication hardware that helps these devices collate data, analyze data (when needed), and transfer data amongst themselves. Even with the existence of IoT in making things easier for users and with the introduction of newer variants of IoT, several security and privacy challenges are introduced. In the rapidly evolving landscape of the Internet of Things (IoT), ensuring secure data sharing has become a critical concern. Attribute-based encryption (ABE) has emerged as a promising cryptographic technique for addressing security challenges in IoT environments. Attribute-Based Encryption (ABE) is a cryptographic method that provides public key encryption and access control based on attributes allocated. ABE can be used to encrypt data transmitted between IoT devices and the cloud. In situations where several devices have to interact with each other (e.g., smart home interacting with the user’s hospital IoT system), an intranet of things is formed, and these data is stored in the cloud. ABE can serve as a secure means of transmitting this data since these devices already possess unique attributes that can grant users access control. In this thesis, we aim to present a systematic review of the Attribute-Based Encryption techniques specifically designed for secure data sharing in IoT environments. The objective of this review is to analyze and synthesize existing research, identify trends, and highlight key findings in the field. Therefore, the document survey is chosen as the research strategy. PRISMA framework is followed in searching the eligible literature in 5 databases (Springer, ACM Digital library, Google Scholar, IEEE, Research Gate, Research Square, and Science Direct), with a final set of 30 articles retrieved from ACM Digital Library, IEEE, and Science Direct, all included for analysis. The results show insights on the several ABE approaches used in implementing a secure data sharing framework with access control (which involves enforcing policies that help data owners determine who can and cannot access their data), data privacy (which involves measures taken to ensure that confidentiality, integrity, and availability of any shared data), and data security (which involves practices that help protect any form of shared data from unauthorized access, tamper, or disclosure) in IoT devices.

Deep learning has shown excellent performance in image recognition, speech recognition, natural language processing and other fields over the recent decades. Cryptography is a technical science that studies the preparation and decoding of ciphers. With the development of artificial intelligence, people pay more and more attention to whether artificial intelligence can be applied to cryptography. A Google team designed a multiagent system a few years ago, which includes encrypting neural network, cracking network and eavesdropping network. Based on symmetric encryption, through deep learning training, the system achieves that the cracker can crack the encrypted text with minimal error and prevent the eavesdropper from cracking the plaintext. This research has aroused the interest of many scholars. Based on the research of the system, this thesis discusses the basic principle and related experiments of the system, as well as the design based on asymmetric encryption and the application in multiparty systems. / Djupinlärning har visat utmärkta resultat inom bildigenkännande, taligenkänning, naturligt språkbehandling och andra områden under de senaste årtiondena. Kryptografi är en teknisk vetenskap som studerar beredning och avkodning av chiffer. I och med utvecklingen av artificiell intelligens lägger människor allt större vikt vid huruvida artificiell intelligens kan användas för kryptografi. Ett Googleteam designade ett multiagent system för några år sedan, vilket inkluderar kryptering av neuralt nätverk, sprickbildning av nätverk och avlyssning. På grundval av symmetrisk kryptering, genom djup inlärning, uppnår systemet att dekrypteraren kan avkoda den krypterade texten med minimala fel och förhindra att tjuvlyssnaren gör detsamma. Denna forskning har väckt intresse hos många forskare. På grundval av systemets forskning diskuteras i denna tes den grundläggande principen och relaterade experiment med systemet, liksom den konstruktion som bygger på asymmetrisk kryptering och tillämpningen i flerpartssystem.