Abstract: The invention relates to an access control method controlling access to a broadcast digital dataflow previously scrambled. The method according to the invention includes the following steps: On transmission: generating an entitlement control message R-ECMc for recording the content of the flow as a function of a key KRc and at least one criterion CRR defining a right to the record, generating an entitlement control message P-ECMc controlling access to play back the content of the recorded flow as a function of a key KPc and at least one criterion CRP defining a right to play back, and on reception: analysing the messages P-ECMc and P-ECMc, authorizing the recording and playback if the criteria CRR and CRP are verified.

Abstract: A method of establishing a session key Ks for a session between a unit for descrambling scrambled multimedia signals and a removable cryptographic unit, wherein: —one of the units sends (steps 166, 184) the other unit a message containing a received random number, a term ? and a signature of the random number and/or the term a produced using a private key K3pr, then—the other unit verifies (steps 168, 192) the signature using a public key K3pu corresponding to the private key (K3pr) and compares (steps 174, 198) the random number received to that sent, and—if the signature is incorrect or if the random number received does not match that sent, then the subsequent steps for establishing the session key are not carried out.

Abstract: The invention relates to a method for controlling access to a transmitted digital data stream which has been previously encrypted. The inventive method comprises the following steps: upon transmission, generation of a message R-ECMc for controlling the right of access to the recording of the contents of the flow according to a key KRc, in addition to at least one criterion CRR defining a right to said recording; generation of a message P-ECMc controlling the right of access to playback of the contents of the flow recorded according to a key KPc and at least one criterion CRP defining a right to playback, and upon reception, analysis of messages R-ECMc, and P-ECMc, and authorization of recording and playback if criteria CRR and CRP are verified.

Abstract: The invention relates to a process for protecting against the re-routing of a multiplex transmitted by an operator to at least one subscriber, comprising the following stages: on transmission, associating with said multiplex at least one authentication message protected by a cryptographic function susceptible of being generated exclusively by the operator, associating with said message at least one variable data item the evolution of which over time is pre-defined by the operator, and on reception, analysing the authentication message, authorising access to the multiplex if said message is authentic and integral, and if the evolution of the variable data item is coherent, otherwise, prohibiting multiplex access.

Abstract: The invention relates to a remote control protocol for a local action to generate a command message (OM), which permits a broadcaster to control a local action in at least one receiving station comprising: a step for transmission of an authorisation message (HM) from the broadcaster to the receiving station(s) and a verification step (4) in said receiving station(s), for transmitted authenticity parameters and addresses, with regard to parameters memorised in each of said receiving stations. The invention is characterised in that the authorisation message (HM) comprises a generation action (CM), at the level of the receiving station(s), a command message (OM), calculated locally and said protocol also comprises, conditional on the verification step (4), an interpretation step (10) of said action (CM) transmitted with said authorisation message (HM) and a local generation step (20) for a command message (OM) in response to said interpretation step (10).

Abstract: A method and an equipment for allocating to a television program, which is already conditionally accessed, a complementary conditional access. The television program is first received by means provided with access entitlements and the control words are restored. Complementary access control messages and complementary entitlement management messages corresponding to a complementary access control system are built up. The initial unmodified television program is rebroadcast, together with the complementary messages related to the complementary access control system.

Abstract: A random access memory (RAM) comprises memory cells each including an RS type flip-flop having complementary data inputs and transistors for forcing the flip-flop by that one of two data wires which is at a given level (high level for example) when a selection wire is at a first given level (high level for example). The flip-flop is connected to an output wire by circuitry for maintaining the output wire at the high level as long as the selection wire is at the first level and for causing the output wire to take the level corresponding to the condition of the flip-flop when the selection wire is brought to the other level. The transistors are preferably N-MOS for higher speed.

Abstract: The device is for use in demultiplexing a MAC/PACKET incoming signal which comprises successive bursts of digital data distributed into packets, each packet consisting of useful data and a header having a channel number indicating one of a plurality of service components to which said packet is assigned, a continuity index IC and a header error protection code. The device has a circuit for generating all error-free configurations of a selected channel number and IC and corresponding to a respective service component; an encoder for encoding all error-free configurations into all possible theoretical header configurations having the error protection code; and a computer for computing the Hamming distances between each packet header in the incoming signal and all theoretical header configurations. Those packets for which the Hamming distance is not greater than a predetermined value are directed to an output interface.

Abstract: An image memory graphic terminal comprising an image memory constituted by memory planes, each plane incorporating a matrix system of memory points, a sequencer, a graphic display processor, a video signal generator, a video display receiver, a management microcomputer.According to the invention, the terminal also comprises a system for writing or recording in the image memory image texture signals, said system comprising(A) a circuit for processing the access cycle to the image memory, said circuit incorporating:(A.sub.1) a circuit for the transmission, with a time lag, of the signals for controlling the access cycle to the memory,(A.sub.2) a shaping circuit (42),(B) a circuit for the determination of the word to be written into the memory, incorporating:(B.sub.1) an operation parametrization circuit,(B.sub.2) a computing circuit being able to: . calculate two coordinates .alpha.* and .beta.* from addresses x, y and signals .DELTA.X, .DELTA.Y, .DELTA.H, .DELTA.V, off.sub.x, off.sub.y(B.sub.