Thesis: This thesis consists of three chapters and is organized in two parts. Each part deals with a particular theoreticalissue of firms' private information.The first part of the thesis is devoted to the architecture of global warming policies and firms' private information.The first chapter analyses which global agreement can be implemented in presence of two-tiers asymmetry of information coming from both countries and domestic firms. We impose several key constraints on the design of such a regulatory policy: heterogeneity of countries, two-tier private information both at domestic and international levels and full participation. We derive the optimal first and second-best agreement. It is shown that the optimal global agreement does not always entail a uniform price for carbon. In presence of domestic firm's private information, the second-best agreement entails prices for carbon that differ from one country to another. We thereby highlight the failure of the Law of One Carbon Price. In the second part of the thesis that comprises two chapters, I study the interaction between two communication tools — price signaling and third-party disclosure — that firms may use to reveal their private information to consumers. The second chapter examines a third-party disclosure that consists in a certification handled by a middleman: a certifier. A monopolist has the choice between paying for that disclosure or using price to signal quality. The strategic certifier is either a for-profit entity or an entity that defends the monopolist' interest. I first show that the structure of audit costs incurred by the middlemen affects the type of monopolist that chooses certification. I then show that the characteristics of the certification —audit probability and certification fee— vary with the motivation of the strategic middleman. More specifically, a for-profit certifier, whenever it is possible, will not audit and put the highest feasible fee while a certifier defending the monopolist will audit with a certain probability and select the lowest possible fee. This chapter thereby contributes to a better understanding of the certification industry.The last chapter studies a third-party disclosure that consists of two steps: certification and labeling. It involves two middlemen — the certifier and the owner of the label — and it includes a certification fee and a price for the label. A monopolist has the choice between paying for that disclosure or signaling quality through price.I derive the disclosure when the certifier is a for-profit private entityand the label owner is private either a for-profit entity or an entity that defends the monopolist' interest. I show that, when the label owner defends the monopolist, the price of that label and the sharing of the surplus depend on the nature of certifiers' competition. In particular, I find that, a label owner defending the monopolist in order to prevent the certifier from capturing the surplus should favor competition between certifiers or, when that is not possible, monetize the label.