Composability in Watermarking Schemes

TL;DR

This paper explores the concept of composability in software watermarking schemes, proposing a framework to combine watermarking methods for cryptographic building blocks to secure larger protocols.

Contribution

It introduces a formal set of requirements for composability in watermarking schemes and demonstrates how to construct larger, secure watermarking protocols from smaller components.

Findings

Established a formal framework for watermarking scheme composability

Derived new watermarking schemes for complex protocols based on building blocks

Showed that composability enhances security and flexibility in watermarking applications

Abstract

Software watermarking allows for embedding a mark into a piece of code, such that any attempt to remove the mark will render the code useless. Provably secure watermarking schemes currently seems limited to programs computing various cryptographic operations, such as evaluating pseudorandom functions (PRFs), signing messages, or decrypting ciphertexts (the latter often going by the name ``traitor tracing''). Moreover, each of these watermarking schemes has an ad-hoc construction of its own. We observe, however, that many cryptographic objects are used as building blocks in larger protocols. We ask: just as we can compose building blocks to obtain larger protocols, can we compose watermarking schemes for the building blocks to obtain watermarking schemes for the larger protocols? We give an affirmative answer to this question, by precisely formulating a set of requirements that allow for composing watermarking schemes. We use our formulation to derive a number of applications.