A Privacy-Preserving Framework for Managing Mobile Ad Requests and Billing Information Organizations are starting to realize the significant value of advertising on mobile devices, and a number of systems have been developed to exploit this opportunity. From a privacy perspective, practically all systems developed so far are based either on a trusted third-party model or on a generalized architecture. We propose a system for delivering context, location, time, and preference-aware advertisements to mobiles with a novel architecture to preserve privacy. The main adversary in our model is the server distributing the ads, which is trying to identify users and track them, and to a lesser extent, other peers in the wireless network. When a node is interested in an ad, it forms a group of nearby nodes seeking ads and willing to cooperate to achieve privacy. Peers combine their interests using a shuffling mechanism in an ad-hoc network and send them through a primary peer to the ad-server. In this way, preferences are masqueraded to request custom ads, which are then distributed by the primary peer. Another mechanism is proposed to implement the billing process without disclosing user identities.