Choose this if you have, for instance, checked the ID card of the person, and have verified that they are in possession of the secret key (e. g. by sending them encrypted mail and asking for it to be decrypted).
Seleccioneu això si heu, p. ex. comprovat la targeta d' identificació de la persona, i heu verificat que té la clau secreta (p. ex. enviant- li correus que hagi encriptat i demanant- li que els desencripti).