Method and system for ensuring the security of telephone call management centers

System enabling a call control center to which services offered by separate service providers are related to identify the service provider's customers calling the call control center through telephone equipment connected to a communications network, the system comprising:

• a card the same size as a credit card, said card being customized by identifiers specific to each card and to each customer, and provided to customers;
• said card comprising:
• emission means for emitting acoustic DTMF identification signals, said emission means being activatable by the customer with an activation element accessible from an outside of said card,
• encryption means for at least partly encrypting said acoustic signals and varying said acoustic signals each time said signals are emitted,
• an incremental counter interconnected to said emission means and said encryption means such that said acoustic identification signals are encrypted as a function of a state of said incremental counter, said incremental counter being incremented by at least one unit whenever said card emits said acoustic signals,
• a microphone in said telephone equipment for receiving said acoustic signals and transforming said acoustic signals into electronic signals that can be transmitted through the communications network,
• computer means connected to said communications network, said computer means comprising:
• a database containing said identifiers specific to each said card and each said customer,
• means for storing a state C(p,m) of said incremental counter at a time of a last validated operation,
• means for comparing a state C(p,n) of said incremental counter emitted during a current operation with said state C(p,m) of said incremental counter, such that said computer means refuses the current operation if C(p,n) is less than or equal to C(p,m), and continues the current operation of C(p,n) is greater than C(p,m),
• said processing means and said comparison means including means for calculating expected electronic signals S′(p,n) as a function of said state C(p,n) of said incremental counter and said identifiers, and comparing said expected electronic signals with said transmitted electronic signals,
• wherein said acoustic signals are at least partly encrypted into a function S(p,n) as a function of C(p,n), and wherein if said transmitted electronic signals S(p,n) conform with said expected electronic signals S′(p,n), the customers may then be connected to the service provider.