Abstract: The invention consists of writing at least one piece of information ?I! and an image ?I'! thereof into the accessible memory zone Ac of a portable object (1). This image ?I'! is obtained by implementing a program of encipherment of the information ?I!. This program takes into account at least the one piece of information ?I!, a first datum ?Ks! that is external to the portable object and furnished to encipherment circuits (21) under the control of the person writing the information, and a second datum ?Sid! that is diversified for each portable object (1). Later certification consists of verifying that an image ?I'! has been obtained with the aid of the first and second data, so as to deduce from this that the associated information ?I! is original.

Abstract: A process of authentication, by an outside medium, of a portable object connected to that medium via a transmission line and a system for carrying out the process. To authenticate a portable object (7) connected to a terminal linked to the outside medium by a transmission line, the outside medium (1) manages a control table (11) containing a non-secret piece of data (N.sub.7) specific to each object that can be identified, as well as a parameter (E.sub.a ) and a result (R.sub.a) entered in the control table during the preceding authentication of the object. A new parameter (E.sub.b), produced by the medium during authentication, is used to calculate a new result (R.sub.b) in the object. The old result is recalculated. If it matches the one in the table (11), the object is authenticated, and the new parameter (E.sub.b) and result (R.sub.b) are entered in the control table in place of the preceding ones. The process is well suited for use in protecting computer networks.

Abstract: The object of the invention is a process for certifying the origin of at least one item of information stored in the memory of a first electronic device such as a portable card and transmitted to a second electronic device such as a portable card, and a system for implementing said process. An individual A controls a card C.sub.A which has a memory M.sub.A that contains an item of information I.sub.A specific to the individual A. An individual B controls a card C.sub.B which has a memory M.sub.B that contains an item of information I.sub.B specific to individual B. In order for individual B, who receives the information I.sub.A, to be certain of the origin of this information I.sub.A, each of the two cards C.sub.A and C.sub.B calculates a result R related to the information I.sub.A, to a secret set (S) shared by the two cards, to a random number (E.sub.B) supplied by individual B, and to a parameter J which, in turn, is related to the two items of information (I.sub.A, I.sub.