A method of establishing a trustworthiness level of a participant in a communication connection between a first communication partner and a second communication partner is proposed whereby the communication behavior is adapted to the established trustworthiness level. The participant is equipped with a trustworthiness certificate and a therefrom separated securely stored participant private key. The first communication partner receives the trustworthiness certificate from the participant wherefrom the trustworthiness level is derived and established. The first communication partner tests whether the trustworthiness certificate belongs to the participant by using the participant private key. In case the trustworthiness certificate is confirmed by the test to belong to the participant, the first communication partner communicates the established trustworthiness level to the second communication partner. Then, at least one parameter of the communication behavior is chosen in dependence of the established trustworthiness level.