Method and device for performing electronic transactions

A method for performing electronic transactions via a communications network, in which a sender of transaction messages is assigned a smart card with an associated unique identity and a private key stored in the card in a protected manner, and in which an associated public key is kept generally available, characterised in that in connection with an electronic transaction under the sender's own control, preferably through his own input of message information, the sender, independently of any connection to a communications network and without computer dialogue with a receiver, creates, on the basis of entered transaction information, a transaction message, which contains information necessary for the transaction, the transaction message being created in the smart card with the aid of software previously stored in the smart card, and, in his smart card, provides the created transaction message with his digital signature while using his own private key for subsequent output and transmission of the transaction message.