A method for performing a payment transaction, the method comprising: - receiving a secret for a payment application from an operator's server system (68,85) to a user's terminal (62,84) in response to a successful login to said server system (68,85), - activating a trust card in said user's terminal (62,84) by utilizing said secret for the payment application, said trust card being a virtual trust card comprising an application for controlling access to said payment application, an encryption algorithm and keys for encryption of the payment algorithm, and said activating comprising using said secret for the payment application to set said trust card into a mode where said trust card can communicate with external parties in addition to said server system, - receiving payment data from a point-of-sale terminal (67,81) at the user's terminal (62,84), said payment data relating to said payment transaction, - transmitting said payment data to the operator's server system (68,85) to be verified, said payment data being transmitted in encrypted form encrypted by said secret for said payment application, characterised by - receiving a second secret at the user's terminal (62, 84), said second secret having been formed by the operator's server system if said verification of said payment data produces an acceptable result, said second secret being configured to be used for performing said payment transaction, said second secret being received in encrypted form encrypted by said secret for said payment application, and - transmitting data of the trust card and a combination of a user's secret and said second secret from said user's terminal (62,84) to said point-of-sale terminal (67,81) for checking and performing the payment transaction through the point-of-sale terminal (67,81). - receiving a secret for a payment application from an operator's server system (68,85) to a user's terminal (62,84) in response to a successful login to said server system (68,85), - activating a trust card in said user's terminal (62,84) by utilizing said secret for the payment application, said trust card being a virtual trust card comprising an application for controlling access to said payment application, an encryption algorithm and keys for encryption of the payment algorithm, and said activating comprising using said secret for the payment application to set said trust card into a mode where said trust card can communicate with external parties in addition to said server system, - receiving payment data from a point-of-sale terminal (67,81) at the user's terminal (62,84), said payment data relating to said payment transaction, - transmitting said payment data to the operator's server system (68,85) to be verified, said payment data being transmitted in encrypted form encrypted by said secret for said payment application, characterised by - receiving a second secret at the user's terminal (62, 84), said second secret having been formed by the operator's server system if said verification of said payment data produces an acceptable result, said second secret being configured to be used for performing said payment transaction, said second secret being received in encrypted form encrypted by said secret for said payment application, and - transmitting data of the trust card and a combination of a user's secret and said second secret from said user's terminal (62,84) to said point-of-sale terminal (67,81) for checking and performing the payment transaction through the point-of-sale terminal (67,81).