Caesarcipher is a commonly known encryption method although it is known for being unsure, even long before computers were invented. Even though it is unsure it can still be used for cryptography, JackTheRidder consists of two main algorithms where one of them is based on the Caesarcipher. With many rotations of Caesarciphers on different parts of texts, like many Vigenerecryptos of different sizes overlapping each other, makes the encryption secure. The other main algorithm of JackTheRidder is based on the Collatz Conejcture, which is a famous unsolved mathematical problem. This algorithm counts the amount of steps it takes before the chosen number reaches 1 and then moves the letter with those steps which results in the encryption. The amount of steps is a result from a positive integer going through Collatz Conjecture, which divides the integer if its even and uses (3𝑥+1)/2 if the integer is odd. The algorithm then moves to the next character to encrypt and adds one to the integer used. JackTheRidder is an encryption method created by the authors of this project and further will be analyzed in this essay. The focus of this essay is to analyze how Collatz Conjecture and Caesarcipher functions in encryption methods. JackTheRidder is going to be examined through literature study and experiments. There are three criterias that JackTheRidder is going to be analyzed from; security, robustness and efficiency. The results indicate that JackTheRidder needs to be optimized and be written in machine code for it to be able to get better implemented in society. JackTheRidder is proven to be better than AES in the chi2 test which is an indicator that it might be a viable option for replacement. Overall in the experiments, JackTheRidder held a high level which is a positive outcome but still it is not guaranteed to be secure enough to be implemented into the society at this stage of developement.

Purpose – The purpose of this study is partly to illustrate how the AES encryption methods ECB and CTR affect the computational speed when using the GPGPU framework Cuda, but also to clarify the advantages and disadvantages between the different AES encryption modes. Method – A preliminary study was conducted to obtain empirical data on the AES encryption modes ECB and CTR. Data from the study has been analyzed and compared to determine the various aspects of the AES encryption modes and to create a basis for determining the advantages and disadvantages between them. The preliminary study has been carried out systematically by finding scientific works by searching databases within the subject. An experiment has been used as a method to be able to extract execution time data for the GPGPU framework Cuda when processing the AES encryption modes. Experiment were chosen as a method to gain control over the variables included in the study and to see how these variables change when they are consciously influenced. Findings – The findings of the preliminary study show that CTR is more secure than the ECB, but also considerably more complex, which can lead to integrity risks when implementation is done incorrectly. In the experiment, computational speeds are produced when the CPU memory sends to the GPU memory, the encryption on the GPU and how long it takes for the GPU memory to send to the CPU memory. This is done for both CTR and ECB in encryption and decryption. The result of the analysis shows that the ECB is faster than CTR in encryption and decryption. The calculation speed is higher with the ECB compared to the CTR. Implications – The experiment shows that CTR is slower than the ECB. But the most amount of time spent in encryption for both modes are the transfers between the CPU memory and the GPU memory. Limitations – The file sizes of the files tested only goes up to about 1 gigabyte which gave small computation times.

The fourth generation cellular mobile broadband, Long-Term Evolution (LTE), provides high speed Internet via Internet Protocol (IP). Today’s wireless infrastructure paves the way to a connected society where high speed Internet is seamlessly available at all times for anyone to use. To achieve this, a mobile service subscriber can no longer be bound to a single network provided by a single operator. Thus, roaming constitutes a key pillar in shaping the connected society Local Breakout (LBO) Voice over Long-Term Evolution (VoLTE) roaming enables a mobile service subscriber to breakout from its home network, and to use network services in a visited network. LBO requires control signalling and user data to be routed over several Public Land Mobile Networks (PLMNs), thus making mobile service subscriber’s the subject of Lawful Intercept (LI) across multiple networks. This thesis project investigates the possibility of using Multimedia Internet KEYing (MIKEY) and Secure Real-Time Transport Protocol (SRTP) to encrypt the payload of VoLTE media packets. More specifically, a Law Enforcement Monitoring Provider (LEMP) is designed, implemented, and evaluated. LEMP is deployed within a cell phone and serves to distribute cryptographic key shares to Trusted Third Parties (TTPs), i.e. multiple escrow agents, entrusted to store these cryptographic key shares. The result preserves the requirements for LI despite the fact that there may be multiple network operators involved. Moreover, the experiments show that the distribution time depends primarily on network latency rather than the time required to split the cryptographic key in chunks; hence the approach is usable in practice. / Den fjärde generationens mobila bredband, Long-Term Evolution (LTE), möjliggör användandet av höghastighetsinternet över Internet Protocol (IP). Dagens trådlösa infrastrukturer banar väg för ett fritt och lättillgängligt digitalt samhälle där alla kan vara uppkopplade samtidigt. För att uppnå global trådlös infrastruktur måste mobilabonnenten ha möjlighet att utnyttja flera andra trådlösa nätverk än det nätverk som teleoperatören binder dem till. Därför utgör fri roaming en viktig del i utvecklingen av framtidens globala trådlösa infrastrukturer. Local Breakout (LBO) Voice over Long-Term Evolution (VoLTE) är en roamingarkitektur som gör det möjligt för en mobilabonnent att kopplas upp från en teleoperatörs nät till en annans. LBO kräver att kontrollsignaler och användardata skickas mellan flera operatörer innan trafiken når sitt mål, och därmed utsätts mobilabonnenten för laglig avlyssning av elektronisk information på flera platser samtidigt. Det här examensarbetet undersöker möjligheten att använda Multimedia Internet KEYing (MIKEY) och Secure Real-Time Transport Protocol (SRTP) för att kryptera mediatrafik i VoLTE. Under arbetets gång utvecklas och utvärderas en Law Enforcement Monitoring Provider (LEMP). LEMP är placerad i en mobiltelefon och distribuerar delar av krypteringsnycklar till flera betrodda tredje parter (till flera escrow agents). Detta gör det möjligt att uppfylla kraven för laglig avlyssning av elektronisk information även när flera teleoperatörer avlyssnar användardata och kontrollsignaler. Resultatet visar att distribueringstiden primärt beror på nätverkslatens, och inte på den tid det tar att fördela krypteringsnyckeln i mindre delar. Därför kan den här metoden användas i praktiken.