This paper addresses the security of optimistic fair exchange in a multi-user setting. While the security of public key encryption and public key signature schemes in a single-user setting guarantees the security in a multi-user setting, we show that the situation is different in the optimistic fair exchange. First, we show how to break, in the multi-user setting, an optimistic fair exchange sc...

We develop a structural theory of beliefs and behavior that relaxes the assumption of time consistency in beliefs. Our theory is based on the trade-off between optimism, which raises anticipatory utility, and objectivity, which promotes efficient actions. We present it in the context of allocating work on a project over time, develop testable implications to contrast it with models assuming tim...

Aiming at solving the problems in the mobile computing environment such as low bandwidth, frequent disconnection and low battery capacity, we propose an improved optimistic transaction processing method -the virtual time optimistic transaction processing protocol. This protocol improves the performance of optimistic transaction processing by extending the concept of committability or, more spec...

Discrete relaxation is frequently used to compute the fixed point of a discrete system where / is monotonic with respect to some partial order Given an appropriate init ial value for X, discrete relaxation repeats the assignment until a fixed point for / is found. Monotonicity of / with respect to is a sufficient (but in general not necessary) condition for iterative, hill-climbing techniques s...

Optimistic fair exchange (OFE) is a protocol for solving the problem of exchanging items or services in a fair manner between two parties, a signer and a verifier, with the help of an arbitrator which is called in only when a dispute happens between the two parties. In almost all the previous work on OFE, after obtaining a partial signature from the signer, the verifier can present it to others...

In this paper we make an analogy between the time that storage must be maintained in a optimistic simulation and the blocking time in a conservative simulation. By exploring this analogy, we design two new Global Virtual Time (GVT) protocols for Time Warp systems. The rst protocol is based on null message clock advancement in conservative approaches. Our main contribution is a new protocol insp...

We consider the problem of reinforcement learning over episodes of a finitehorizon deterministic system and as a solution propose optimistic constraint propagation (OCP), an algorithm designed to synthesize efficient exploration and value function generalization. We establish that when the true value function Q⇤ lies within the hypothesis class Q, OCP selects optimal actions over all but at mos...