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Trust-management systems address the authorization problem in distributed systems. They offer several advantages over other approaches, such as support for delegation and making authorization decisions in a decentralized manner. Nonetheless, trust-management systems such as KeyNote and SPKI/SDSI have seen limited deployment in the real world. One reason for this is that both systems require a public-key infrastructure (PKI) for authentication, and PKI has proven difficult to deploy, because each user is required to manage his/her own private/public key pair. The key insight of our work is that issuance of certificates in trust-management systems, a task that usually requires public-key cryptography, can be achieved using secret-key cryptography as well. We demonstrate this concept by showing how SPKI/SDSI can be modified to use Kerberos, a secret-key based authentication system, to issue SPKI/SDSI certificates. The resulting trust-management system retains all the capabilities of SPKI/SDSI, but is much easier to use because a public key is only required for each SPKI/SDSI server, but no longer for every user. Moreover, because Kerberos is already well established, our approach makes SPKI/SDSI-based trust management systems easier to deploy in the real world. [ABSTRACT FROM AUTHOR]

We suggest a general paradigm of using large-scale distributed computation to solve difficult problems, but where humans can act as agents and provide candidate solutions. We are especially motivated by problem classes that appear to be difficult for computers to solve effectively, but are easier for humans; e.g., image analysis, speech recognition, and natural language processing. This paradigm already seems to be employed in several real-world scenarios, but we are unaware of any formal and unified attempt to study it. Nonetheless, this concept spawns interesting research questions in cryptography, algorithm design, human computer interfaces, and programming language / API design, among other fields. There are also interesting implications for Internet commerce and the B24b model. We describe this general research area at a high level and touch upon some preliminary work; a more extensive treatment can be found in [6]. [ABSTRACT FROM AUTHOR]

There are a variety of well-known models for access control developed for purposes like formally modeling the access rights on files, databases, and web resources. However, the existing models provide an inadequate representation of a number of concepts that are important when modeling privacy rights in distributed systems. We present an analog of the access control matrix designed to model such concepts. Our formalism, which we call a privacy system, empashizes the management of data and actions that affect the privacy of subjects. We motivate privacy systems, describe them mathematically, and illustrate their value in an architecture based on Personal Digital Rights Management (PDRM), which uses DRM concepts as a foundation for the specification and negotiation of privacy rights. This illustration is carried out throuh a case study of a privacy-respecting system for location based services. Our prototype, which we call AdLoc, manages advertising interupts on PDAs based on their location as determined by WiFi sightings in accordance with contracts written in the DRM language XrML. [ABSTRACT FROM AUTHOR]

This paper uses delaying functions, functions that require significant calculation time, in the development of a one-pass lottery scheme in which winners are chosen fairly using only internal information. Since all this information may be published (even before the lottery closes), anyone can do the calculation and therefore verify that the winner was chosen correctly. Since the calculation uses a delaying function, ticket purchasers cannot take advantage of this information. Fraud on the part of the lottery agent is detectable and no single ticket purchaser needs to be trusted. Coalitions of purchasers attempting to control the winning ticket calculation are either unsuccessful or are detected. The scheme can be made resistant to coalitions of arbitrary size. Since we assume that coalitions of larger size are harder to assemble, the probability that the lottery is fair can be made arbitrarily high. The paper defines delaying functions and contrasts them with pricing functions [8] and time-lock puzzles [15]. [ABSTRACT FROM AUTHOR]

We present a protocol for unlinkable serial transactions suitable for a variety of network-based subscription services. The protocol prevents the service from tracking the behavior of its customers while protecting the service vendor from abuse due to simultaneous or "cloned" usage from a single subscription. We present variants of the protocol supporting pay-per-use transactions within a subscription. We describe other applications including third-party subscription management, multivendor package sales, proof of group membership, and voter registration. [ABSTRACT FROM AUTHOR]

Phishing is an attack in which victims are lured by official looking email to a fraudulent web-site that appears to be that of a legitimate service provider. The email also provides victims with a convincing reason to log-on to the site. If users are fooled into logging-on, then the attacker is provided with the victims' authentication information for the legitimate service provider, often along with personal information, such as their credit-card data, checking account information or social security data. Successful phishing attacks can result not only in identity and asset theft, but also in more subtle attacks that need not be directly directly harmful to the victim but which have negative consequences for society (for example: money laundering). [ABSTRACT FROM AUTHOR]