Method and system for secure distribution of protected data using elliptic curve systems

A method of decrypting information at a user computer system comprising a processor, a memory, an input device and an output device, comprising the steps of:

• storing, in the memory of the user computer system, information representing an elliptic curve;
• generating a user key;
• transmitting, to a processing center, a message including the user key;
• receiving, from the processing center, a message comprising the index of a first point on an elliptic curve and information based on the user key which relates the first point on the elliptic curve to a second point on the elliptic curve;
• determining a first point on the elliptic curve based on the received index of the first point;
• determining the second point on the elliptic curve using the information based on the user key which relates the first point on the elliptic curve to the second point on the elliptic curve;
• generating an index of the second point, the index corresponding to the decrypted information.

A processing center computer system for encrypting information, the encrypted information to be sent to a user computer system, comprising:

• a memory storing information to be encrypted and information relating to an elliptic curve;
• the processing center computer system programmed to:
• accept a user key received from the user computer system;
• select a first point on the elliptic curve having an index representing the information to be encrypted;
• determine a second point on the elliptic curve related to the first point on the elliptic curve based on the user key;
• and
• transmit to the user a message comprising the index of the second point on the elliptic curve and information based on the user key which relates the second point on the elliptic curve to the first point on the elliptic curve as encrypted information for the user computer system.

A user computer system for decrypting information from a processing center, comprising:

• a memory storing information relating to an elliptic curve;
• the user computer system programmed to:
• generate a user key;
• transmit, to the processing center a message including the user key;
• receive, from the processing center, a message comprising the index of a first point on the elliptic curve and a delta key;
• generate a center key which is the sum of the user key and information based on the user key which relates the first point on the elliptic curve to a second point on the elliptic curve;
• determine the first point on the elliptic curve based on the index of the first point;
• determine the second point on the elliptic curve using the information based on the user key which relates the first point on the elliptic curve to the second point on the elliptic curve;
• and
• generate an index of the second point, the index corresponding to the decrypted information.

A program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform method steps for decrypting information at a user computer system, the method steps comprising:

• storing, in the memory of the user computer system, information representing an elliptic curve;
• providing to the user a user key;
• requesting a user to provide information to be decrypted;
• accepting from the user the information to be decrypted, the information comprising the index of a first point on an elliptic curve and information based on the user key which relates the first point on the elliptic curve to a second point on the elliptic curve;
• determining a first point on the elliptic curve based on the index of the first point;
• determining the second point on the elliptic curve using the information based on the user key which relates the first point on the elliptic curve to the second point on the elliptic curve;
• generating an index of the second point, the index corresponding to the decrypted information.