Process for performing transactions among a number of participants, in which every participant has a unique pseudonym assigned to him, in which a participant's pseudonym comprises his encrypted transaction data, a participant's transaction data being transaction-limiting data, without knowledge of which a transaction cannot be performed and which remains the same for every transaction of the participant, in which the assignment of a pseudonym to a participant, and the key required to decrypt the transaction data are stored in the form of a participant record on a notary server, the process comprising supplying an application program installed on a piece of terminal equipment of a first participant and at least one transaction server, the application program being registered to the first participant, so that his pseudonym is known to the application program, a parameter uniquely identifying the first participant's piece of terminal equipment being contained in the first participant's record, the application program being able to determine the parameter uniquely identifying the first participant's piece of terminal equipment, the process comprising the following steps: - Optical reading, by the application program, of a QR code containing the pseudonym of a second participant; - Collection of transaction parameters by the application program; - Sending the pseudonyms of the first and second participant, the transaction parameters, and the parameter uniquely identifying the piece of terminal equipment from the application program to a transaction server over the Internet; - Sending the pseudonyms and the parameter uniquely identifying the piece of terminal equipment from the at least one transaction server to the notary server; - Identification of the participants by the notary server on the basis of the pseudonyms; - Checking whether the parameter uniquely identifying the piece of terminal equipment is contained in the first participant's record; - If the parameter uniquely identifying the piece of terminal equipment is contained in the first participant's record, decryption of the transaction contained in the participants' pseudonym; - Sending the participants' transaction data to the at least one transaction server by the notary server; - Performance, by the at least one transaction server, of the transaction between the first participant and the at least one other participant on the basis of the transaction parameters. - Optical reading, by the application program, of a QR code containing the pseudonym of a second participant; - Collection of transaction parameters by the application program; - Sending the pseudonyms of the first and second participant, the transaction parameters, and the parameter uniquely identifying the piece of terminal equipment from the application program to a transaction server over the Internet; - Sending the pseudonyms and the parameter uniquely identifying the piece of terminal equipment from the at least one transaction server to the notary server; - Identification of the participants by the notary server on the basis of the pseudonyms; - Checking whether the parameter uniquely identifying the piece of terminal equipment is contained in the first participant's record; - If the parameter uniquely identifying the piece of terminal equipment is contained in the first participant's record, decryption of the transaction contained in the participants' pseudonym; - Sending the participants' transaction data to the at least one transaction server by the notary server; - Performance, by the at least one transaction server, of the transaction between the first participant and the at least one other participant on the basis of the transaction parameters.