Due to the increasing pervasiveness of the mobile web, it is possible to send and receive mails with mobile devices. Content of digital communication should be encrypted to prevent eavesdropping and manipulation. Corresponding procedures use cryptographic keys, which have to be exchange previously. It has to be ensured, that a cryptographic key really belongs to the person, who it is supposedly assigned to. Within the scope of this thesis a concept for a smartphone application to exchange cryptographic keys was designed. The concept consists of a specification of a component-based framework, which can be used to securely exchange data in general. This framework was extended and used as the basis for a smartphone application. The application allows creating, managing and exchanging cryptographic keys. The Near Field Communication is used for the exchange. Implemented security measures prevent eavesdropping and specific manipulation. In the future the concept and the application can be extended and adjusted to be used in other contexts.