Secure data transmission method

A method of performing secure data transmission between respective sending and receiving telecommunication system terminals that are connected with one another through a server device, each of said terminals being associated with an interface device operative for transferring data between the respective terminal and a respective system subscriber card that includes at least a data storage and a processor for processing data obtained from the data storage and from the respective terminal and operable for issuing output data to the respective terminal, each of the subscriber cards being individualized prior to issuance thereof to a respective individual subscriber by storing in its data storage a unique code key data string, with at least an association between each individual subscriber and the unique code key data string stored on that individual subscriber's individualized subscriber card being stored in a repository accessible to the server device, comprising the steps of:

• (A) at a respective sending terminal:
• (i) providing a unique original sender challenge data string;
• (ii) transferring the original sender challenge data string to the respective individualized sender subscriber card;
• (iii) processing the original sender challenge data string and the unique code key data string on the respective sender subscriber card to obtain a sender response data string that has a first relationship to the original sender challenge data string, which relationship is unique to the respective sending subscriber card;
• (iv) encrypting original data that is to be securely transmitted by the sending subscriber using one of the sender response data string and the challenge data string to provide encrypted data;
• and
• (v) transmitting the encrypted data and the other of the sender challenge data string and the response data string to the server device;
• (B) at the server device:
• (i) receiving from the sending terminal the encrypted data and the other of the sender challenge data string and the response data string;
• (ii) retrieving from the repository the code key data string associated with the subscriber card of the sending subscriber;
• (iii) utilizing the unique first relationship of the retrieved code key data string to obtain the one from the other of the sender challenge data string and the response data string;
• (iv) decrypting the received encrypted data utilizing the thus obtained one of the sender response data string and the challenge data string;
• (v) retrieving from the repository the unique recipient subscriber code key data string associated with the subscriber card issued to the intended recipient subscriber;
• (vi) providing a unique server challenge data string;
• (vii) processing the server challenge data string and the retrieved unique recipient subscriber code key data string to obtain a server response data string that has a second relationship to the original server challenge data string, which relationship is tailored for the respective intended recipient subscriber card;
• (viii) re-encrypting the server-decrypted data using one of the server response data string and the server challenge data string to provide server re-encrypted data;
• and
• (ix) transmitting the server re-encrypted data, together with the other of the server challenge data string and the server response data string, to a respective receiving terminal associated with the recipient subscriber;
• and
• (C) at the respective receiving terminal:
• (i) receiving from the server device the server re-encrypted data and the other of the server challenge data string and the server response data string;
• (ii) transferring the other of the server challenge data string and the server response data string to the respective individualized recipient subscriber card;
• (iii) processing the received other of the server challenge data string and the server response data string and the unique code key data string on the respective recipient subscriber card to obtain a resultant recipient data string corresponding to the one of the server challenge data string and the server response data string used for the encryption at the server device;
• and
• (iv) decrypting the server re-encrypted data utilizing the one of the received server response data string and the server challenge data string to provide a replica of the original data.

A method of performing secure data transmission of messages between individual subscribers of a telecommunications system that includes individual terminals linked by a server device, comprising the steps of:

• establishing a multiplicity of correlations each defining a relationship for pairing an arbitrary challenge data string in a unique and consistent manner with a different corresponding response data string;
• making each of said multiple correlations available to a corresponding one of the individual subscribers, and all of said multiple correlations available to the server device in identifying associations with said corresponding individual subscribers;
• apprising the server device of the identities of an originating subscriber and an intended receiving subscriber for a particular transmission;
• cryptographically processing an original message to be conveyed in encrypted form in said particular transmission from the originating subscriber through the server device to the intended receiving subscriber, comprising the steps of:
• generating an originating subscriber pair of the challenge and response data strings at one of said originating subscriber and server device utilizing the correlation associated with the originating subscriber;
• communicating one of the data strings of said originating subscriber pair from said one to the other of said originating subscriber and server device;
• regenerating the other of the data strings of said originating subscriber pair at the other of said originating subscriber and server device from the thus communicated one data string;
• encrypting the message at the originating subscriber using said other of the data strings of the originating subscriber pair;
• posting the encrypted message to the telecommunications system at the originating subscriber;
• receiving the encrypted message at the server device;
• decrypting the encrypted message at the server device using the said other of the data strings of the originating subscriber pair to recover the message;
• and
• cryptographically reprocessing the thus recovered message at the server device and at the receiving subscriber in a manner corresponding to that employed in the performance of said cryptographically processing step at the originating subscriber and at the server, utilizing the correlation associated with the receiving subscriber in place of that associated with the originating subscriber.