An Overview of Cryptography (Updated Version, 3 March 2016)

There are many aspects to security and many applications, ranging from secure commerce and payments to private communications and protecting passwords. One essential aspect for secure communications is that of cryptography...While cryptography is necessary for secure communications, it is not by itself sufficient. This paper describes the first of many steps necessary for better security in any number of situations. A much shorter, edited version of this paper appears in the 1999 edition of Handbook on Local Area Networks published by Auerbach in September 1998

Input-shrinking functions: theory and application

In this thesis, we contribute to the emerging field of the Leakage-Resilient Cryptography by studying the problem of secure data storage on hardware that may leak information, introducing a new primitive, a leakage-resilient storage, and showing two different constructions of such storage scheme provably secure against a class of leakage functions that can depend only on some restricted part of the memory and against a class of computationally weak leakage functions, e.g. functions computable by small circuits, respectively. Our results come with instantiations and analysis of concrete parameters. Furthermore, as second contribution, we present our implementation in C programming language, using the cryptographic library of the OpenSSL project, of a two-party Authenticated Key Exchange (AKE) protocol, which allows a client and a server, who share a huge secret file, to securely compute a shared key, providing client-to-server authentication, also in the presence of active attackers. Following the work of Cash et al. (TCC 2007), we based our construction on a Weak Key Exchange (WKE) protocol, developed in the BRM, and a Password-based Authenticated Key Exchange (PAKE) protocol secure in the Universally Composable (UC) framework. The WKE protocol showed by Cash et al. uses an explicit construction of averaging sampler, which uses less random bits than the random choice but does not seem to be efficiently implementable in practice. In this thesis, we propose a WKE protocol similar but simpler than that one of Cash et al.: our protocol uses more randomness than the Cash et al.'s one, as it simply uses random choice instead of averaging sampler, but we are able to show an efficient implementation of it. Moreover, we formally adapt the security analysis of the WKE protocol of Cash et al. to our WKE protocol. To complete our AKE protocol, we implement the PAKE protocol showed secure in the UC framework by Abdalla et al. (CT-RSA 2008), which is more efficient than the Canetti et al.'s UC-PAKE protocol (EuroCrypt 2005) used in Cash et al.'s work. In our implementation of the WKE protocol, to achieve small constant communication complexity and amount of randomness, we rely on the Random Oracle (RO) model. However, we would like to note that in our implementation of the AKE protocol we need also a UC-PAKE protocol which already relies on RO, as it is impossible to achieve UC-PAKE in the standard model. In our work we focus not only on the theoretical aspects of the area, providing formal models and proofs, but also on the practical ones, analyzing instantiations, concrete parameters and implementation of the proposed solutions, to contribute to bridge the gap between theory and practice in this field

Body language, security and e-commerce

Security is becoming an increasingly more important concern both at the desktop level and at the network level. This article discusses several approaches to authenticating individuals through the use of biometric devices. While libraries might not implement such devices, they may appear in the near future of desktop computing, particularly for access to institutional computers or for access to sensitive information. Other approaches to computer security focus on protecting the contents of electronic transmissions and verification of individual users. After a brief overview of encryption technologies, the article examines public-key cryptography which is getting a lot of attention in the business world in what is called public key infrastructure. It also examines other efforts, such as IBM’s Cryptolope, the Secure Sockets Layer of Web browsers, and Digital Certificates and Signatures. Secure electronic transmissions are an important condition for conducting business on the Net. These business transactions are not limited to purchase orders, invoices, and contracts. This could become an important tool for information vendors and publishers to control access to the electronic resources they license. As license negotiators and contract administrators, librarians need to be aware of what is happening in these new technologies and the impact that will have on their operations

Secure communications over insecure channels based on short authenticated strings

We propose a way to establish peer-to-peer authenticated communications over an insecure channel by using an extra channel which can authenticate very short strings, e.g. 15 bits. We call this SAS-based authentication as for authentication based on short authenticated strings. The extra channel uses a weak notion of authentication in which strings cannot be forged nor modified, but whose delivery can be maliciously stalled, canceled, or replayed. Our protocol is optimal and relies on an extractable or equivocable commitment scheme. This approach offers an alternative (or complement) to public-key infrastructures, since we no longer need any central authority, and to password-based authenticated key exchange, since we no longer need to establish a confidential password. It can be used to establish secure associations in ad-hoc networks. Applications could be the authentication of a public key (e.g. for SSH or PGP) by users over the telephone, the user-aided pairing of wireless (e.g. BIuetooth) devices, or the restore of secure associations in a disaster case, namely when one remote peer had his long-term keys corrupte

Native Cryptography in the Browser, An Exploratory Approach

As applications move from the desktop to the web browser, security needs to be taken into consideration. The new Web Crypto API provides native support for web applications to perform cryptographic operations and key management functions. Client side cryptographic support is a critical component in the future development of secure web based applications. This thesis presents an exploration of the Web Crypto API. The aim of this research was to determine the feasibility of developing complex cryptographic applications in the browser. This evaluation was performed by building an end to end encrypted messaging system that implements the off the record (OTR) messaging protocol. This thesis also proposes Joey’s Web Crypto Library (JWCL), a wrapper library around the native Web Crypto API that provides network portable output, secure default options, and a class based modern interface. In this thesis the Web Crypto API is shown to be capable of supporting the development of a functional, proof of concept, end to end encrypted secure messaging system in the browser. JWCL succeeds in providing a high level, simple yet elegant interface to the low level Web Crypto API

The Meeting of Acquaintances: A Cost-efficient Authentication Scheme for Light-weight Objects with Transient Trust Level and Plurality Approach

Wireless sensor networks consist of a large number of distributed sensor nodes so that potential risks are becoming more and more unpredictable. The new entrants pose the potential risks when they move into the secure zone. To build a door wall that provides safe and secured for the system, many recent research works applied the initial authentication process. However, the majority of the previous articles only focused on the Central Authority (CA) since this leads to an increase in the computation cost and energy consumption for the specific cases on the Internet of Things (IoT). Hence, in this article, we will lessen the importance of these third parties through proposing an enhanced authentication mechanism that includes key management and evaluation based on the past interactions to assist the objects joining a secured area without any nearby CA. We refer to a mobility dataset from CRAWDAD collected at the University Politehnica of Bucharest and rebuild into a new random dataset larger than the old one. The new one is an input for a simulated authenticating algorithm to observe the communication cost and resource usage of devices. Our proposal helps the authenticating flexible, being strict with unknown devices into the secured zone. The threshold of maximum friends can modify based on the optimization of the symmetric-key algorithm to diminish communication costs (our experimental results compare to previous schemes less than 2000 bits) and raise flexibility in resource-constrained environments.Comment: 27 page

TRENDS IN ELECTRONIC COMMERCE SECURITY: A MANAGERIAL BRIEF AND TEACHING NOTE

The Internet and similar networks provide new infrastructures for communications and commerce. These open networks interconnect computers across many different organizations with dramatically lower communications and distributed applications development costs. This motivates businesses to transfer commercial activity from closed private networks to open networks like the Internet. However, open network architectures are vulnerable to a number of different security threats. While many different hardware and software solutions exist to secure transactions over the Internet, greater consensus is required by companies and consumers on the processes, organizations and application of existing technical solutions for secure electronic commerce. Greater consensus on security among trading parties will lower the costs of electronic commerce and accelerate its deployment on the Internet.Information Systems Working Papers Serie