In a method and a system for a computer-based and secured communication between data processing units a sender selects an alphanumeric and/or image data set, which is sent to at least one contact selected by sender out of a contact list. The selected contact is assigned an authorization by the sender, wherein the authorization is stored on the server. The selected alphanumeric and/or image data set is pixelated before sending it to the at least one selected contact. The pixelated data set is transmitted to a data processing unit of the at least one contact. The data processing unit of the at least one selected contact communicates with the server and the authorization is requested or obtained. At authorization of the contact, the pixelation of the pixelated data set, sent by sender, is removed.