Commercial trusted third parties (TTPs) may increase their bottom line by watering down their validation procedures because they assume no liability for lapses of judgement. Consumers bear the risk of misplaced trust. Reputation loss is a weak deterrent for TTPs because consumers do not choose them - web shops and browser vendors do. At the same time, consumers are the source of income of these parties. Hence, risks and rewards are not well-aligned. Towards a better alignment, we explore the brokering of connection insurances and transaction insurances, where consumers get to choose their insurer. We lay out the principal idea how such a brokerage might work at a technical level with minimal interference with existing protocols and mechanisms, we analyze the security requirements and we propose techniques to meet these requirements.

The design of modern desktop operating systems is based on the assumption that a single user controls input and output devices at a time. This is also the case for access control, where applications inherit the privileges from the user that started them. This is not sufficient for multi-user collaboration on Single Display Groupware (SDG) or tabletop systems. For these we suggest a more fine-grained access control method based on the user that is interacting with an application.

Multi-touch displays are particularly attractive for collaborative work because multiple users can interact with applications simultaneously. However, unfettered access can lead to loss of data confidentiality and integrity. For example, one user can open or alter files of a second user, or impersonate the second user, while the second user is absent or not looking. Towards preventing these attacks, we explore means to associate the touches of a user with the user's identity in a fashion that is cryptographically sound as well as easy to use. We describe our current solution, which relies on a ring-like device that transmits a continuous pseudorandom bit sequence in the form of infrared light pulses. The multi-touch display receives and localizes the sequence, and verifies its authenticity. Each sequence is bound to a particular user, and all touches in the direct vicinity of the location of the sequence on the display are associated with that user.