Many real-world applications use credentials such as passwords as means of user authentication. When accessed from untrusted public terminals, such applications are vulnerable to credential sniffing attacks, as shown by recent highly publicized compromises. In this paper, we describe a secure remote terminal application that allows users possessing a trusted device to delegate their credentials for performing a task to a public terminal without being in danger of disclosing any long-term secrets. Instead, the user gives the terminal the capability of performing a task temporarily (as long as the user is in its proximity). Our model is intuitive in the sense that the user exposes to the untrusted terminal only what he sees on the display, and nothing else. We present the design and implementation of such a system. The overhead - in terms of additional network traffic - created by introducing a trusted third party is a moderate 12%.

Consider a CIA agent who wants to authenticate herself to a server but does not want to reveal her CIA credentials unless the server is a genuine CIA outlet. Consider also that the CIA server does not want to reveal its CIA credentials to anyone but CIA agents - not even to other CIA servers. We first show how pairing-based cryptography can be used to implement such secret handshakes. We then propose a formal definition for secure secret handshakes, and prove that our pairing-based schemes are secure under the Bilinear Diffie-Hellman assumption. Our protocols support role-based group membership authentication, traceability, indistinguishability to eavesdroppers, unbounded collusion resistance, and forward repudiability. Our secret-handshake scheme can be implemented as a TLS cipher suite. We report on the performance of our preliminary Java implementation.

Digital content distribution systems will enable business models in the near future that cannot be predicted today.I n t h i s paper, we i d e n tify a new security problem that can be crucial to this enablement.The problem arises from the con icting privacy and integrity goals of middlemen in digital distribution chains.Our solution is a novel system design that incorporates obfuscated digital contracts, semi-trusted contract certi ers, and zero-knowledge proofs of arithmetic relations.Our implementation and timing experiments demonstrate that our solution is practical and eÆcient.

We show that if the private exponent d used in the RSA (Rivest-Shamir-Adleman (1978)) public-key cryptosystem is less than N/sup 0.292/ then the system is insecure. This is the first improvement over an old result of Wiener (1990) showing that when d is less than N/sup 0.25/ the RSA system is insecure. We hope our approach can be used to eventually improve the bound to d less than N/sup 0.5/.