A secured method for controlling the opening of lock devices, including the following steps:
- a) by a management site (10):
- a1) generation of digital data (DATA);
- a2) encryption, according to a symmetrical method, of a field (40) containing said digital data, by an encryption algorithm and with an encryption key;
- and
- a3) generation of a message (DKE) containing the encrypted field;
- b) transmission of the message, via a communication network, to a portable device (16) held by a user and storage of this message in a memory of the portable device;
- c) transmission of the message, by a short-range transmission technique, from the portable device (16) to a secured module (20) generator of digital accreditations, coupled to a lock device (18);
- d) by the secured module (20) generator of digital accreditations, analysis of the message by:
- d1) decryption, according to said symmetrical method, of the encrypted field (40);
- d2) checking of the message compliance with an internal reference memorized in the secured module;
- and
- d3) in case the message is proved compliant at step d2), generation by the secured module of a digital accreditation adapted to control the lock device unlocking upon recognition of the compliance of this accreditation,
- the method being characterized in that:
- said encryption and said decryption use a common key memorized both by the management site and by the secured module, the management site (10) and secured module (20) each memorizing (14, 24) a corresponding list of said common keys;
- for the encryption of step a2), the manager site operates a previous selection of a key among said list of keys memorized by the management site;
- the message generated at step a3) further contains an encryption key identifier (Kj), identifying the key used for the encryption of step a2), and
- step d) comprises a step of previous reading of the encryption key identifier, and the decryption of step d1) is operated with the key identified by said reading, selected among said list of keys memorized by the secured module,
- the method being also characterized in that it further comprises a procedure for updating, by substitution or/and addition of new keys, said list of keys memorized in a memory of the secured module, procedure in which:
- during the generation of a message (DKE), the management site encapsulates into the encrypted field (40) of this message:
- i) the new keys (Kn+1, Kn+2, . . . ), or
- ii) an identifier of a modifying function selected among several modifying functions adapted to permit the calculation of the new keys;
- the message is transmitted to the secured module addressee of the news keys via a portable device during an unlocking, by this portable device, of the lock coupled to this addressee secured module;
- and
- upon reception of this message, the secured module:
- i) updates the keys memorized in the memory of the secured module, or, respectively
- ii) recalculates the new keys based on the received modifying function identifier, and updates the keys memorized in the memory of the secured module with the so-recalculated keys.