Abstract: A method of automatically controlling fraud in an electronic transaction system. When a user initiates a session in the electronic transaction system, an element is generated and stored in a database in association with information identifying the user. Each time during the session the user commands the execution of an operation, an equation is determined that is satisfied by the element stored in the database. When a sufficient given number of operations has been effected, the system of equations consisting of the equations determined as above is solved to deduce the element. By consulting the database, the corresponding information identifying the user is deduced from the element obtained in this way.

Abstract: A portable device, a terminal, a system, and a method of storing data relating to transactions by terminals (1) of merchants in portable loyalty devices (3) of customers of at least one group comprising at least one merchant, said transaction being stored by the terminal (1) of said merchant in the portable device (3) by executing the following steps in any order: storing a first record corresponding to said transaction encrypted with an encryption key (C1) of the customer; and storing a second record corresponding to said transaction encrypted with a key (M1) associated with said group to which said merchant belongs.

Abstract: A method of automatically controlling fraud in an electronic transaction system. When a user initiates a session in the electronic transaction system, an element is generated and stored in a database in association with information identifying the user. Each time during the session the user commands the execution of an operation, an equation is determined that is satisfied by the element stored in the database. When a sufficient given number of operations has been effected, the system of equations consisting of the equations determined as above is solved to deduce the element. By consulting the database, the corresponding information identifying the user is deduced from the element obtained in this way.

Abstract: A method of granting authorization to access a resource, comprising the following steps: connecting a user to an access management center to request that authorization to access a given resource be granted to a third party equipped with a mobile terminal, defining particular conditions governing the access authorization, the user sending coordinates of the third party's mobile terminal to the access management center, the access management center generating access data as a function of the resource and said particular conditions, and sending said access data to the third party's mobile terminal to enable the latter to be identified by an access control device associated with said resource in order to authorize the third party to access that resource.