Private Asymmetric Fingerprinting: A Protocol with Optimal Traitor Tracing Using Tardos Codes

Abstract

AbstractActive fingerprinting schemes were originally invented to deter malicious users from illegally releasing an item, such as a movie or an image. To achieve this, each time an item is released, a different fingerprint is embedded in it. If the fingerprint is created from an anti-collusion code, the fingerprinting scheme can trace colluding buyers who forge fake copies of the item using their own legitimate copies. Charpentier, Fontaine, Furon and Cox were the first to propose an asymmetric fingerprinting scheme based on Tardos codes – the most efficient anti-collusion codes known to this day. However, their work focuses on security but does not preserve the privacy of buyers. To address this issue, we introduce the first privacy-preserving asymmetric fingerprinting protocol based on Tardos codes. This protocol is optimal with respect traitor tracing. We also formally define the properties of correctness, anti-framing, traitor tracing, as well as buyer-unlinkability. Finally, we prove that our protocol achieves these properties and give exact bounds for each of them.KeywordsFingerprintingWatermarkingAnti-collusion codeTardos codePrivacyAnonymity