International Business Machines Corporation

Amit Sahai

Shanmugasundaram Ravikumar

Andrew Stephen Tomkins

Sridhar Rajagopalan

Cynthia Dwork

Ran Canetti

Moses Samson Charikar

A sender computer maps a randomized concatenation of a message &#x3bc; to a point 'x' in space using a function that renders it infeasible that a second message can be mapped nearby the message &#x3bc;. The function can be a collision intractable or non-collision intractable function that maps the message to a point 'x' on a widely-spaced grid, or the function can map the message to a point &#x201c;x&#x201d; of an auxiliary lattice. In either case, the sender computer, using a short basis (essentially, the private key) of a key latticefinds a lattice point &#x201c;y&#x201d; that is nearby the message point &#x201c;x&#x201d;, and then at least the points &#x201c;x&#x201d;, &#x201c;y&#x201d;, and message are sent to a receiver computer. To verity the signature, the receiver computer simply verifies that &#x201c;y&#x201d; is part of the lattice using a long basis (essentially, the public key), and that the distance between &#x201c;x&#x201d; and &#x201c;y&#x201d; is less than a predetermined distance, without being able or having to know how the lattice point &#x201c;y&#x201d; was obtained by the sender computer.

Digital signature system and method based on hard lattice problem

An anonymous credential system which requires a user who is asserting a credential to have knowledge of the master key of the user who was originally granted that credential. In order for a user to transfer the ability to assert any one of their credentials to another user, they must also transfer their master key to that same user. The master key, however, provides such unlimited rights to its holder that a user is strongly motivated not to share their master key with anyone else. In this manner, anonymous credentials become non-transferrable because a user cannot transfer a credential without transferring their entire electronic identity.

Non-transferable anonymous credentials

Growing community of inventors

Cambridge, MA, United States of America

Amit Sahai