—The advent of distributed and ad-hoc-connected systems such as in Ambient Intelligence applications confronts developers with the question on how to specify QoS- and security policies beforehand, without knowing the exact capabilities and requirements of the platforms which will be present at run time. Especially when peers need to adhere to an appropriate trade-off between security and performance, on-the-fly negotiation protocols are required to allow peers to autonomously agree on a common policy. In this paper we present a framework for secure multi-party decision protocols based on auctions. Besides a lightweight implementation, our main focus was on integrating security features for avoiding manipulation of the agreement and reducing the attractiveness of denial of service attacks. As a prototype, we have realized two different auction protocols on top of our framework and used them in a mobile collaboration scenario using a set of Android devices. Experiments with the protot...