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A vast majority of popular communication protocols for the internet employ the use of TLS (Transport Layer Security) to secure communication. As a result, there have been numerous efforts including the introduction of Certificate Transparency logs and Free Automated CAs to improve the SSL certificate ecosystem. Our work highlights the effectiveness of these efforts using the Certificate Transparency dataset as well as certificates collected via full IPv4 scans. We show that a large proportion of invalid certificates still exists and outline reasons why these certificates are invalid and where they are hosted. Moreover, we show that the incorrect use of template certificates has led to incorrect SCTs being embedded in the certificates. Taken together, our results emphasize continued involvement for the research community to improve the web's PKI ecosystem. / Master of Science / Security and Privacy for communication over the internet is increasingly important. TLS (Transport Layer Security) is the most popular protocol used to secure communications over the internet today. This work explores how this protocol has evolved over the past 9 years and how effective the measures undertaken by the community have been to improve the adherence to best practices in the wild. TLS employs the use of certificates to initialize secure communication and make sure the other party is indeed who they say they are. We show that while security has improved over the years, a majority of certificates are invalid and outline reasons why. We also observe the growth of Certificate Transparency logs and show how the use of template certificates cause unexpected issues. Taken together, our results emphasize a continued involvement for the research community to improve the TLS certificate ecosystem.

This thesis introduces a new tower field representation, optimal tower fields (OTFs), that facilitates efficient finite field operations. The recursive direct inversion method presented for OTFs has significantly lower complexity than the known best method for inversion in optimal extension fields (OEFs), i.e., Itoh-Tsujii's inversion technique. The complexity of OTF inversion algorithm is shown to be O(m^2), significantly better than that of the Itoh-Tsujii algorithm, i.e. O(m^2(log_2 m)). This complexity is further improved to O(m^(log_2 3)) by utilizing the Karatsuba-Ofman algorithm. In addition, it is shown that OTFs are in fact a special class of OEFs and OTF elements may be converted to OEF representation via a simple permutation of the coefficients. Hence, OTF operations may be utilized to achieve the OEF arithmetic operations whenever a corresponding OTF representation exists. While the original OTF multiplication and squaring operations require slightly more additions than their OEF counterparts, due to the free conversion, both OTF operations may be achieved with the complexity of OEF operations. Furthermore, efficient finite field algorithms are introduced which significantly improve OTF multiplication and squaring operations. The OTF inversion algorithm was implemented on the ARM family of processors for a medium and a large sized field whose elements can be represented with 192 and 320 bits, respectively. In the implementation, the new OTF inversion algorithm ran at least six to eight times faster than the known best method for inversion in OEFs, i.e., Itoh-Tsujii inversion technique. According to the implementation results obtained, it is indicated that using the OTF inversion method an elliptic curve scalar point multiplication operation can be performed at least two to three times faster than the known best implementation for the selected fields.

Secure communication is critical to many applications. To this end, various security goals can be achieved using elliptic/hyperelliptic curve and pairing based cryptography. Polynomial multiplication is used in the underlying operations of these protocols. Therefore, as part of this thesis different recursive algorithms are studied; these algorithms include Karatsuba, Toom, and Bernstein. In this thesis, we investigate algorithms and implementation techniques to improve the performance of the cryptographic protocols. Common factors present in explicit formulae in elliptic curves operations are utilized such that two multiplications are replaced by a single multiplication in a higher field. Moreover, we utilize the idea based on common factor used in elliptic curves and generate new explicit formulae for hyperelliptic curves and pairing. In the case of hyperelliptic curves, the common factor method is applied to the fastest known even characteristic hyperelliptic curve operations, i.e. divisor addition and divisor doubling. Similarly, in pairing we observe the presence of common factors inside the Miller loop of Eta pairing and the theoretical results show significant improvement when applying the idea based on common factor method. This has a great advantage for applications that require higher speed.

The main goal of this master's thesis is building of web portal for presentation basic cryptography algorithms. Those algorithms would be explained in the theoretical page in the first place. After that, they would be demonstrated by scripts. One part of this project is designing simplified theoretical element for basic impletion portal of information. Next part is creating web portal by one of the free available CMS´s systems. Programming language JAVA would be used as an instrument for creating demonstration scripts. For creating animations will be used the Flash animation tool. Target of formed web portal is creating community of expert public. It would make new articles, scripts and knowledge. This way, the portal would be kept current. The section which would include failure the most widely used algorithms and instructions how to eliminate it will be part of portal.

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International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / SSL protocol is one industrial standard to protect data transferred securely on Internet. Firstly SSL is analyzed, according to its characteristics, one solution plan on mobile bank based on SSL is proposed and presented, in which GPRS technology is adopted and elliptic curve algorithm is used for the session key, finally several functional modules of mobile bank are designed in details and its security is analyzed.

The purpose of the investigation is to determine the most effective solution, which allows safe storing and transmitting of financial information in terms of execution speed, resistance to hacking and ease of implementation. Research object is subject area related to the transfer of encrypted financial information like: encryption algorithms, algorithm of hashing functions, algorithm of electronic digital signature. The result of research is the software implementation of the server and client for sending encrypted information. Also client could only encrypt/decrypt information. The main part of research is to find the most suitable algorithm for transfer of encrypted banking information. The solution has been implemented on the Java programming language in programming environment IntelliJ IDEA 8, using Java Cryptography Extension (JCE) for digital signature.

International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / It is an increasing requirement that commercial satellite telemetry data product be protected from unauthorized access during transmission to ground stations. While the technology (cryptography) to secure telemetry data product is well known, the software infrastructure to support such security is costly, and very customized. Further, many software packages have difficulty interoperating. The Common Data Security Architecture [1] [2] [3] (originally proposed by the Intel Corporation, and now adopted by the Open Group), is a set of common cryptographic [4] and public key infrastructure (PKI) application programming interfaces (APIs) which will facilitate better cryptographic interoperability as well as making cryptographic resources more readily available in telemetry post processing environments.

In this work, we study the cryptographic primitive: signcryption, which combines the functionalities of digital signatures and public-key encryption. We first propose two generic transforms from meta-ElGamal signature schemes to signcryption schemes. These constructions can be thought of as generalisations of the signcryption schemes by Zheng and Gamage et al. Our results show that a large class of signcryption schemes are outsider IND-CCA2 secure and insider UF-CMA secure. As a by-product, we also show that the meta-ElGamal signature schemes, for which no previous formal security proofs have been shown, are UF-CMA secure. We then propose a modification of one of the transforms in order to achieve insider IND-CCA2 security in addition to insider UF-CMA security. This modification costs just one extra exponential operation. In particular, we can apply this modification to the Zheng signcryption scheme to make it fully insider secure. Finally, we propose a generic transform from a two-key signcryption scheme to a one-key signcryption scheme while preserving both confidentiality and unforgeability. Our result shows that if we have an insider IND-CCA2 and UFCMA secure two-key signcryption scheme, then it can be turned into an insider IND-CCA2 and UF-CMA secure one-key signcryption scheme. We also show that an insider IND-CCA2 and UF-CMA secure one-key signcryption scheme induces a secure combined public-key scheme; that is, a combination of a signature scheme and a public-key encryption scheme that can securely share the same key pair. Combining previous results suggests that we can obtain a large class of insider secure one-key signcryption schemes from meta-ElGamal signature schemes, and that each of them can induce a secure combined public-key scheme.