Abstract: A method and a system for authenticating an electronic tag by a host communicating with this tag via a reader, including: calculating, on the tag side, a first digital signature using at least one first function shared by the tag and the reader, taking into account at least one first secret key known by the electronic tag and the reader only; transmitting the first signature to the reader; calculating, on the reader side, a second digital signal using at least one second function, different from the first function and shared by the reader and the host, taking the first signature into account; transmitting the second signature to the host; and checking, on the host side, the coherence between the second signature and a validation value calculated based on said second function and on a second secret key known by the host and by a single element selected from among the tag and the reader.

Abstract: A circuit includes a microprocessor, an MPEG decoder for decoding an image sequence, and a memory common to the microprocessor and to the decoder. The circuit also includes a circuit for evaluating a decoder delay, a control circuit for, if the decoder delay is greater than a predetermined level, granting the decoder a memory access priority, and otherwise, granting the microprocessor the memory access priority.

Abstract: In a method of teletext management, the data processing is separated into at least two tasks. A first task deals with the processing of the data from the rough extraction, and a second task carries out the rest of the data processing. The first task activates the second task by an interrupt with a priority lower than an interrupt activating the first task. The method thus enables the interruption of the second task to carry out a following first task, thus eliminating any timing drift that may cause the loss of the data packet coming from the rough extraction.

Abstract: In integrated circuits, to modify the operation of the charge pumps or voltage step-up circuits, they are sent a variable frequency signal at the input with the aim of breaking the regularity of the pulse train that enters the charge pump. This limits the risks of entry into resonance and limits radiation at a given frequency. The variable frequency signal is typically produced by a logic circuit and by a main oscillator whose transmission of certain pulses is masked by the combined action of different masking signals. The duty cycle ratios of the masking signals are less than that of the signal from the main oscillator. Such duty cycle ratios are preferably produced following the passage of a signal to a lower frequency than that of the signal of the main oscillator in a circuit for the detection of high transitions.