Efficient Deep Neural Network Verification with QAP-Based ZkSNARK

In MLaaS, DNN models are kept in a server operated by the service provider and inputs to the DNN models are provided by the clients. Such inputs are used to execute the DNN models and classification results are sent back to the client. In MLaaS, the DNN model owner does not reveal the DNN model parameters to the client. MLaaS there are a few trust problems: (a) The server may not be secure and an attacker may send manipulated classification results to the client. In the case of safety-critical systems using such classification in the decision-making process, an attacker may specifically manipulate the classification result to disrupt the operations of the safety-critical system, (b) The server may intentionally send wrong or random classification results without executing the DNN model to respond to a massive number of classification requests from the clients. In this paper, we investigate the problem of verifying DNN model execution by the service provider in an MLaaS paradigm. A proof of DNN model execution will prove that given an input, the DNN model is executed to generate the classification result by providing sequences of outputs of all functions used in the DNN model. As the service provider in MLaaS does not share the DNN model with the client, we need to verify DNN function outcomes without the knowledge of DNN function parameters. Hence zero-knowledge proof can be used for verifying DNN model execution. In this paper, we use Zero-Knowledge Succinct Non-interactive Arguments of Knowledge (zk-SNARKs) which reduces the size of proof and complexity of proof verification considerably. In particular, we use a quadratic arithmetic program-based zkSNARK for DNN model verification. Our main results in this paper are as follows: (a) We have developed a DNN model execution verification method using a QAP-based zkSNARK. (b) We prove that the verification protocol is correct and privacy-preserving. (c) We analyzed the cost of using such a verification protocol.