Computer of the type comprising a motherboard, comprising a first microprocessor (μP 1), a working memory associated to the first microprocessor and a connector, and a card with a cryptographic function, introduced in the connector of the motherboard, and comprising a second microprocessor (μP 2), a key memory, and a module for securing data by encryption/decryption and/or signature/verification of signature, wherein this module comprises a plurality of securing circuits (11, 12, 13), and at least one common interfacing module, located between the first microprocessor and the plurality of securing circuits, wherein the securing circuits are connected in parallel to said common interfacing module, and each making it possible to ensure the encryption/decryption or respectively the calculation/verification of signature, of data received from or respectively sent to said common interfacing module, wherein each securing circuit comprises: - an input/output sub-module for securing (11a, 12a, 13a) interconnected to said common interfacing module; and, - a specific sub-module for encryption/decryption or respectively for calculation/verification of signature (11b, 12b, 13b), characterized in that each securing circuit (11, 12, 13) constituting a securing automaton operates, under the control of the first microprocessor (μP 1) using the common interfacing module, in direct memory access mode in the working memory, and in that the first microprocessor (μP 1) is suitable for, in order to drive said securing circuit: - initializing an automaton by communication of an address of a zone in the working memory allocated to said automaton; - enter a command block to be executed in the zone in the working memory allocated to an initialized automaton; - transmitting to the common interfacing module a start command that activates a selection command generated by an initialized automaton, wherein the selection command consists of a command for reading in the zone in the working memory allocated to said initialized automaton, wherein the selection command is transmitted by the specific sub-module for encryption/decryption to the input/output sub-module for securing and to the common interfacing module, and in that the input/output sub-module for securing (11a, 12a, 13a) is adapted for reading in the working memory the command block and for communicating the command block to the specific sub-module for encryption/decryption (11b, 12b, 13b) for execution. - an input/output sub-module for securing (11a, 12a, 13a) interconnected to said common interfacing module; and, - a specific sub-module for encryption/decryption or respectively for calculation/verification of signature (11b, 12b, 13b), - initializing an automaton by communication of an address of a zone in the working memory allocated to said automaton; - enter a command block to be executed in the zone in the working memory allocated to an initialized automaton; - transmitting to the common interfacing module a start command that activates a selection command generated by an initialized automaton, wherein the selection command consists of a command for reading in the zone in the working memory allocated to said initialized automaton, wherein the selection command is transmitted by the specific sub-module for encryption/decryption to the input/output sub-module for securing and to the common interfacing module,