XACML is commonly used as a policy exchange mechanism, decision engines are available, and verification tools are under development. However, no support for legacy access control systems exists yet. To explore the feasibility to support legacy systems, we designed and implemented a mapping of the IBMreg Tivolireg Access Manager policy language into XACML. Although the Tivoli Access Manager policy language, being ACL-based, is simpler in general, it turned out to be a non-trivial task to encode the interplay of the Tivoli Access Manager policy elements and decision logic within XACML. To achieve this task, we had to come up with a novel use of XACML features.

Anonymous credential systems [8, 9, 12, 24] allow anonymous yet authenticated and accountable transactions between users and service providers. As such, they represent a powerful technique for protecting users' privacy when conducting Internet transactions. In this paper, we describe the design and implementation of an anonymous credential system based on the protocols developed by [6]. The system is based on new high-level primitives and interfaces allowing for easy integration into access control systems. The prototype was realized in Java. We demonstrate its use and some deployment issues with the description of an operational demonstration scenario.

This paper discusses the design, implementation, and deployment of a secure and practical payment system for electronic commerce on the Internet. The system is based on the iKP family of protocols-(i=1,2,3)-developed at IBM Research. The protocols implement credit card-based transactions between buyers and merchants while the existing financial network is used for payment clearing and authorization. The protocols are extensible and can be readily applied to other account-based payment models, such as debit cards. They are based on careful and minimal use of public-key cryptography, and can be implemented in either software or hardware. Individual protocols differ in both complexity and degree of security. In addition to being both a precursor and a direct ancestor of the well-known SET standard, iKP-based payment systems have been in continuous operation on the Internet since mid-1996. This longevity-as well as the security and relative simplicity of the underlying mechanisms-makes the iKP experience unique. For this reason, this paper also reports on, and addresses, a number of practical issues arising in the course of implementation and real-world deployment of a secure payment system.

This paper discusses issues and idiosyncrasies associated with changing passwords and keys in distributed computer systems. Current approaches are often complicated and fail to provide the desired level of security and fault tolerance. A novel and ve

The encrypted key exchange (EKE) protocol is augmented so that hosts do not store cleartext passwords. Consequently, adversaries who obtain the one-way encrypted password file may (i) successfully mimic (spoof) the host to the user, and (ii) mount dictionary attacks against the encrypted passwords, but cannot mimic the user to the host. Moreover, the important security properties of EKE are preserved—an active network attacker obtains insufficient information to mount dictionary attacks. Two ways to accomplish this are shown, one using digital signatures and one that relies on a family of commutative one-way functions.

Authentication and key distribution protocols that utilize weak secrets (such as passwords and personal identification numbers) are traditionally susceptible to guessing attacks whereby an adversary iterates through a relatively small key space and verifies the correct guess. Such attacks can be defeated by the use of public key encryption and careful protocol construction. T. Lomas et al. (Proc. of ACM Symp. on Operating Syst. Principles, 1989) investigated this topic and developed a methodology for avoiding guessing attacks while incurring only moderate overhead. Several issues concerning the proposed solution are discussed here, and modifications that remove some of the constraints (such as synchronized time and state retention by the server) and result in simpler and more efficient protocols are suggested.>