Investigating the Common Authorship of Signatures by Off-Line Automatic Signature Verification Without the Use of Reference Signatures

TL;DR

This paper explores methods for automatic signature verification without reference signatures, aiming to determine common authorship in sets of signatures potentially from multiple signers, and demonstrates promising results surpassing human performance.

Contribution

It introduces three novel methods for off-line signature verification without reference signatures, addressing a challenging scenario in biometric authentication.

Findings

Methods outperform human volunteers in authorship determination.

Encouraging results achieved with publicly available signatures.

Proposed techniques effectively estimate common authorship without reference signatures.

Abstract

In automatic signature verification, questioned specimens are usually compared with reference signatures. In writer-dependent schemes, a number of reference signatures are required to build up the individual signer model while a writer-independent system requires a set of reference signatures from several signers to develop the model of the system. This paper addresses the problem of automatic signature verification when no reference signatures are available. The scenario we explore consists of a set of signatures, which could be signed by the same author or by multiple signers. As such, we discuss three methods which estimate automatically the common authorship of a set of off-line signatures. The first method develops a score similarity matrix, worked out with the assistance of duplicated signatures; the second uses a feature-distance matrix for each pair of signatures; and the last method introduces pre-classification based on the complexity of each signature. Publicly available signatures were used in the experiments, which gave encouraging results. As a baseline for the performance obtained by our approaches, we carried out a visual Turing Test where forensic and non-forensic human volunteers, carrying out the same task, performed less well than the automatic schemes.