This thesis deals with encryption of short text message (SMS) in mobile communication. Introduction is dedicated to overview of the parts of GSM radiotelephone nets and SMS messages transfer . Next chapter is reserved for description of cryptographic methods especially symetric and asymetric encryptografic aproaches. A design of a SMS messages encryption and decryption techniques is in next. For SMS encryption and sign, there is used the asymetric cypher RSA. Encryption use OAEP padding schema. The public key is saved in certificate. The Symbian OS has been choosen as a suitable platform for programming of mobile devices.

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This master thesis project aims to improve the security of managed software developed at SCANIA's research and development group NEVE. The thesis will present several security schemes that can be effective against tampering, theft, and reverse engineering of application. The schemes presented were selected to ensure confidentiality, integrity, authenticity, and authentication of applications. NEVE’s software will be analyzed and compared against state of the art solutions. A theoretical threat analysis will be presented, corroborated by empirical reverse engineering attacks. The final part of this thesis introduces a new security scheme for C# .NET programs operating without requiring an internet connection. / Denna uppsats försöker förbättra säkerheten av [managed software] utvecklad hos SCANIAS forsknings- och utvecklingsgrupp NEVE. Den visar på flera säkerhetslösningar som kan vara effektiva mot manipulation, stöld och omvänd ingenjörskonst av applikationer. De säkerhetslösningar som presenteras valdes för att säkerställa sekretess, integritet, äkthet och autentisering hos applikationer. NEVEs mjukvara kommer att analyseras och ställs mot de allra senaste lösningarna. En teoretisk hotanalys kommer att presenteras, förstärkt med attacker baserat empiriskt omvänd ingenjörskonst. Den sista delen av denna uppsats introducerar en ny säkerhetslösning. Den riktar sig mot program skrivna i C# .NET som inte kräver en uppkoppling mot internet.

In today's interconnected digital landscape, the protection of sensitive information is of great importance. As a result, the field of cryptography plays a vital role in ensuring individuals' anonymity and data integrity. In this context, this thesis presents a comprehensive analysis of symmetric encryption algorithms, specifically focusing on the Advanced Encryption Standard (AES) and Camellia. By investigating the performance aspects of these algorithms, including encryption time, decryption time, and ciphertext size, the goal is to provide valuable insights for selecting suitable cryptographic solutions. The findings indicate that while there is a difference in performance between the algorithms, the disparity is not substantial in practical terms. Both AES and Camellia, as well as their larger key-size alternatives, demonstrated comparable performance, with AES128 showing marginally faster encryption time. The study's implementation also involves encrypting a data set with sensitive information on students. It encrypts the school classes with separate keys and assigns roles to users, enabling access control based on user roles. The implemented solution successfully addressed the problem of role-based access control and encryption of unique identifiers, as verified through the verification and validation method. The implications of this study extend to industries and society, where cryptography plays a vital role in protecting individuals' anonymity and data integrity. The results presented in this paper can serve as a valuable reference for selecting suitable cryptographic algorithms for various systems and applications, particularly for anonymization of usernames or short, unique identifiers. However, it is important to note that the experiment primarily focused on small data sets, and further investigations may yield different results for larger data sets.

<p>Collecting user data is crucial for advancing machine learning, social science, and government policies, but the privacy of the users whose data is being collected is a growing concern. {\em Differential Privacy (DP)} has emerged as the most standard notion for privacy protection with robust mathematical guarantees. Analyzing such massive amounts of data in a privacy-preserving manner motivates the need to study differentially-private algorithms that are also super-efficient.  </p> <p><br></p> <p>This thesis initiates a systematic study of differentially-private sublinear-time and sublinear-space algorithms. The contributions of this thesis are two-fold. First, we design some of the first differentially private sublinear algorithms for many fundamental problems. Second, we develop general DP techniques for designing differentially-private sublinear algorithms. </p> <p><br></p> <p>We give the first DP sublinear algorithm for clustering by generalizing a subsampling framework from the non-DP sublinear-time literature. We give the first DP sublinear algorithm for estimating the maximum matching size. Our DP sublinear algorithm for estimating the average degree of the graph achieves a better approximation than previous works. We give the first DP algorithm for releasing $L_2$-heavy hitters in the sliding window model and a pure $L_1$-heavy hitter algorithm in the same model, which improves upon previous works.  </p> <p><br></p> <p>We develop general techniques that address the challenges of designing sublinear DP algorithms. First, we introduce the concept of Coupled Global Sensitivity (CGS). Intuitively, the CGS of a randomized algorithm generalizes the classical  notion of global sensitivity of a function, by considering a coupling of the random coins of the algorithm when run on neighboring inputs. We show that one can achieve pure DP by adding Laplace noise proportional to the CGS of an algorithm. Second, we give a black box DP transformation for a specific class of approximation algorithms. We show that such algorithms can be made differentially private without sacrificing accuracy, as long as the function has small global sensitivity. In particular, this transformation gives rise to sublinear DP algorithms for many problems, including triangle counting, the weight of the minimum spanning tree, and norm estimation.</p>

This work aims to provide an experimental evaluation of two kleptographic backdoors. The backdoors target the key generation step in Learning with Errors-based crypto algorithms and exploit freedom in choosing the seeds for the algorithm. Based on the descriptions, four variants were implemented, and their detectability was evaluated by measuring their running time and whether the output from the backdoors passed as uniformly random bit strings. Our results show that all variants of the backdoored seed generation were significantly slower than the normal routine, the fastest variant made key generation in Kyber take 10 times as long as normal. All variants did however pass the tests on uniformity. Additionally, previous work describes a countermeasure that makes the backdoors detectable. We have contributed with a description of how the detection could be implemented, and our measurements show that the detection routine makes the key generation approximately 8% slower.

In the digital landscape of today, large amounts of transactions, messaging and different kinds of authorizations are carried out online. To ensure the the integrity and security of these systems, digital signature systems are used to verify the identity of different individuals and entities. As quantum computing threatens to compromise contemporary signature schemes, a new generation of quantum secure signature schemes have been developed. One such scheme is SPHINCS+, which uses hash algorithms to generate and verify its signatures. This study aims to evaluate the utilization of a Field Programmable Gate Array (FPGA) to increase the processing speed of these hash algorithms, thus potentially increasing the speed of the entire signature scheme. The research methodology consisted of implementing the hash algorithms SHA-2 and SHA-3, used in SPHINCS+, on an FPGA. Variations of these implementations were created, utilizing parallelism as well as an efficient hardware pipeline in order to enhance the efficiency of the algorithms. All implementations were then benchmarked against each other and corresponding CPU implementations. The results show that the FPGA solutions increased hash computation times compared to the CPU implementations. While SHA-3 generally showed higher performance than SHA-2, the overall performance drop of both algorithms was significant, suggesting that the implementations require further optimizations in order to be used to accelerate SPHINCS+. / I dagens digitala landskap genomförs stora mängder transaktioner, auktoriseringar och skickanden av olika former av meddelanden. För att säkerställa integritet och äkthet inom dessa system används digitala signatursystem för att verifiera identiteten hos olika aktörer och enheter. Eftersom kvantdatorer hotar att underminera samtida digitala signatursystem har en ny generation kvantsäkra signatursystem utvecklats. Ett sådant system är SPHINCS+, som använder hashalgoritmer för att generera och verifiera dess signaturer. Denna studie syftar till att undersöka användningen av en Field Programmable Gate Array (FPGA) för att öka hashalgoritmernas beräkningshastigheter, och således potentiellt öka hastigheten för hela signatursystemet. Forskningsmetoden inbegrep att implementera hashalgoritmerna SHA-2 och SHA-3, som används inom SPHINCS+, på en FPGA. Dessa lösningar utökades med variationer som använde parallelism och en effektiv hårdvarupipeline för att öka effektiviteten hos algoritmerna. Implementeringarna jämfördes med varandra och ställdes mot jämförliga CPU-implementeringar. Studiens resultat visar att FPGA-implementeringarna förlängde hashberäkningstiderna jämfört med CPU-implementeringarna. SHA-3 visade högre prestanda än SHA-2, men den övergripande prestandaförlusten för båda algoritmerna var betydande. Detta tyder på att implementeringarna kräver ytterligare optimeringar för att kunna användas för att accelerera SPHINCS+.