  With the increasing prevalence of Machine Learning as a Service (MLaaS)
platforms, there is a growing focus on deep neural network (DNN) watermarking
techniques. These methods are used to facilitate the verification of ownership
for a target DNN model to protect intellectual property. One of the most widely
employed watermarking techniques involves embedding a trigger set into the
source model. Unfortunately, existing methodologies based on trigger sets are
still susceptible to functionality-stealing attacks, potentially enabling
adversaries to steal the functionality of the source model without a reliable
means of verifying ownership. In this paper, we first introduce a novel
perspective on trigger set-based watermarking methods from a feature learning
perspective. Specifically, we demonstrate that by selecting data exhibiting
multiple features, also referred to as \emph{multi-view data}, it becomes
feasible to effectively defend functionality stealing attacks. Based on this
perspective, we introduce a novel watermarking technique based on Multi-view
dATa, called MAT, for efficiently embedding watermarks within DNNs. This
approach involves constructing a trigger set with multi-view data and
incorporating a simple feature-based regularization method for training the
source model. We validate our method across various benchmarks and demonstrate
its efficacy in defending against model extraction attacks, surpassing relevant
baselines by a significant margin. The code is available at:
\href{https://github.com/liyuxuan-github/MAT}{https://github.com/liyuxuan-github/MAT}.
