Method and system using combinable computational puzzles as challenges to network entities for identity check

A method for a computer to challenge network entities for identity check, comprising:

• generating a plurality of computational puzzles, the computational puzzles having a form allowing two or more of the computational puzzles to be solved together by combining the two or more computational puzzles into a single combined puzzle, solving the combined puzzle, and deriving solutions to the two or more computational puzzles from a solution to the combined puzzle;
• issuing challenges to the network entities, each challenge including at least one of the computational puzzles and requiring a response in a given response time;
• receiving solutions to the computational puzzles included in the challenges from the respective network entities to which the challenges are issued;
• and
• determining from the solutions received whether two or more of the computational puzzles included in the challenges given to the network entities have been solved together.

A computer-readable medium having computer-executable instructions for a computer in a network to perform steps for responding to challenges issued by other computers in the network, comprising:

• receiving a plurality of challenges from the other computers in the network, each of the challenges including at least one combinable computational puzzle;
• combining the combinable computational puzzles in the challenges into a combined puzzle;
• finding a solution to the combined puzzle;
• deriving solutions to the combinational computational puzzles in the challenges from the solution to the combined puzzle;
• and
• sending the solutions to the combinable computational puzzles to the respective computers from which the corresponding challenges are received.

A method for a computer in a network to respond to challenges issued by other computers in the network, comprising:

• receiving a plurality of challenges from the other computers in the network, each of the challenges including at least one combinable computational puzzle;
• combining the combinable computational puzzles in the challenges into a combined puzzle;
• finding a solution to the combined puzzle;
• deriving solutions to the combinational computational puzzles in the challenges from the solution to the combined puzzle;
• and
• sending the solutions to the combinable computational puzzles to the respective computers from which the corresponding challenges are received.