An entity such as a social networking system generates a dynamically customized user-specific advertisement using an advertisement template and user information from an advertiser. A request is received for an advertisement to display to a user, and the social networking system retrieves an advertisement template (e.g., provided by an advertiser) that includes one or more functions. The social networking system also retrieves user information that can be used to evaluate a value of a function contained in the advertisement. The template and the value of each function are then used to generate a dynamically customized user-specific advertisement for display to the user. These advertisements can be shown to a user while keeping confidential at least some aspect of the user's personal information from the social networking system and/or the advertiser.