A Survey on Device Heterogeneity and Interoperability in Online Signature Verification

Automatic Signature Verification is one of the challenging problems that has remained unsolved for over the past forty years of research. A new challenge gets added due to the widespread use of smartphones, tablets, stylus-enabled devices, and dedicated signature pads used for capturing signatures for authentication purposes. This multi-device biometric setting necessitates addressing device interoperability to ensure consistent and reliable verification performance. This survey provides a comprehensive analysis of multi-device signature verification with a focus on device interoperability issues, systematically reviews existing approaches and publicly available multi-device signature datasets. The survey reveals that device-induced intra-class variations severely degrade verification accuracy and that current solutions only partially mitigate these challenges. Finally, we outline open research problems and future directions aimed at developing device-invariant representations and more comprehensive multi-device datasets. This survey serves as a consolidated reference for researchers working toward reliable and interoperable signature verification in real-world multi-device environments.