Secure Sketch for All Noisy Sources (Noisy)

TL;DR

This paper introduces a secure sketch construction that guarantees security for all noisy sources, including low-entropy ones, with efficient recovery even at high error rates, and links to NP-complete coding problems.

Contribution

We propose a secure sketch construction that is secure for all noisy sources, including zero-entropy sources, with polynomial-time recovery at high error rates.

Findings

Secure sketch is secure for all noisy sources, including zero-entropy.

Efficient polynomial-time recovery algorithm tolerates errors close to 50%.

Connection established between secure sketch construction and NP-complete coding problems.

Abstract

Secure sketch produces public information of its input $w$ without revealing it, yet, allows the exact recovery of $w$ given another value $w'$ that is close to $w$. Therefore, it can be used to reliably reproduce any error-prone secret (i.e., biometrics) stored in secret storage. However, some sources have lower entropy compared to the error itself, formally called "more error than entropy", a standard secure sketch cannot show its security promise perfectly to these kind of sources. This paper focuses on secure sketch. We propose a concrete construction for secure sketch. We show security to all noisy sources, including the trivial source with zero min-entropy. In addition, our construction comes with efficient recovery algorithm operates in polynomial time in the sketch size, which can tolerate high number of error rate arbitrary close to 1/2. Above result acts in conjunction to our derivation on the solution to two NP-complete coding problems, suggesting P=NP.