Abstract: A method and a system for performing a transaction between at least one first party and at least one second party are disclosed. A data network connects data input/output terminals of the parties. In the data network, a secure and trusted transaction server is provided, in which a profile of the parties is registered, having a party identifier identifying a particular party, and authentication data for authenticating the party and data sent by the party. The parties communicate with each other through the transaction server by means of various transaction messages, which are digitally signed using a table of random numbers and a hashing operation, wherein the table of random numbers is generated by reading a token.

Abstract: A transaction system comprises terminal stations which can communicate with a host exchange. In order to improve the communication, concentrators are arranged between the host exchange and the terminal stations. Given functions can be accommodated within the concentrators so that they need not be provided in the terminal station. The concentrators as well as the terminal stations are provided with a security box in order to realize encryption/decryption of the data transport; for the terminal station this box is preferably realized in the form of a smart card which acts as an operator identification element. A customer can identify himself by means of a user identification element, for example a magstripe card or a further smart card. The encryption mechanism is preferably DES.