The paper introduces the concept of functional encryption, a novel form of encryption that allows a user to learn a specific function of encrypted data without learning anything else about the data. The authors define the concept and its security, noting that defining security for functional encryption is non-trivial. They present a game-based definition and show that it is inadequate for certain functionalities. A simulation-based definition is then introduced, which is provably unsatisfiable in the standard model but can be satisfied in the random oracle model. The paper also discusses the relationship between functional encryption and existing encryption concepts such as attribute-based encryption and predicate encryption. It concludes with open problems and future directions, emphasizing the need for more general functionalities and understanding the relative power of different functionalities.The paper introduces the concept of functional encryption, a novel form of encryption that allows a user to learn a specific function of encrypted data without learning anything else about the data. The authors define the concept and its security, noting that defining security for functional encryption is non-trivial. They present a game-based definition and show that it is inadequate for certain functionalities. A simulation-based definition is then introduced, which is provably unsatisfiable in the standard model but can be satisfied in the random oracle model. The paper also discusses the relationship between functional encryption and existing encryption concepts such as attribute-based encryption and predicate encryption. It concludes with open problems and future directions, emphasizing the need for more general functionalities and understanding the relative power of different functionalities.