A method and a system for checking ownership and integrity of an Al model using distributed ledger technology (DLT)

Complete Specification:

The following specification describes and ascertains the nature of this invention and the manner in which it is to be performed.

Field of the invention

[0001] The present disclosure relates to a method of checking integrity and provenance of an Al model using distributed ledger technology (DLT) and a system thereof.

[0002]

Background of the invention

[0003] With the advent of data science, data processing and decision making systems are implemented using artificial intelligence modules. The artificial intelligence modules use different techniques like machine learning, neural networks, deep learning etc. Most of the Al based systems, receive large amounts of data and process the data to train Al models. Trained Al models generate output based on the use cases requested by the user. Typically the Al systems are used in the fields of computer vision, speech recognition, natural language processing, audio recognition, healthcare, autonomous driving, manufacturing, robotics etc. where they process data to generate required output based on certain rules/intelligence acquired through training. [0004] To process the inputs and give a desired output, the Al systems use various models/algorithms which are trained using the training data. Once the Al system is trained using the training data, the Al systems use the models to process the data and generate appropriate result. The models in the Al systems form the core of the system. Lots of effort, resources (tangible and intangible), and knowledge goes into developing these models. It is possible that some adversary may try to steal/extract or modify the Al model when they are deployed in a public domain. Hence there is a need to ascertain the ownership and integrity of the Al model. Further in safety-critical systems, it is also pertinent to ascertain if the model running in the system is intended one or has been tampered with beyond repairable extent.

[0005] There are methods known in the prior arts about leveraging neural network plasticity to embed watermarks to prove its origin or ownership. Patent application US2019370440 AA titled “Protecting deep learning models using watermarking” discloses a framework to accurately and quickly verify the ownership of remotely deployed deep learning models is provided without affecting model accuracy for normal input data. The approach involves generating a watermark, embedding the watermark in a local deep neural network (DNN) model by learning, namely, by training the local DNN model to learn the watermark and a predefined label associated therewith, and later performing a black box verification against a remote service that is suspected of executing the DNN model without permission. The predefined label is distinct from a true label for a data item in training data for the model that does not include the watermark. Black-box verification includes simply issuing a query that includes a data item with the watermark, and then determining whether the query returns the predefined label. However, there is a need to not only verify the ownership and origin but also the integrity of an Al model.

Brief description of the accompanying drawings

[0006] An embodiment of the invention is described with reference to the following accompanying drawings: [0007] Figure 1 illustrates method steps for checking ownership and integrity of an Al model using distributed ledger technology (DLT);

[0008] Figure 2 depicts the proposed system architecture for checking integrity of an Al model using distributed ledger technology (DLT) and a flow chart thereof.

Detailed description of the drawings

[0009] Some important aspects of the Al technology and Al systems can be explained as follows. Depending on the architecture of the implements Al systems may include many components. One such component is an Al module. An Al module with reference to this disclosure can be explained as a component which runs a model. A model can be defined as reference or an inference set of data, which is use different forms of correlation matrices. Using these models and the data from these models, correlations can be established between different types of data to arrive at some logical understanding of the data. A person skilled in the art would be aware of the different types of Al models such as linear regression, naive bayes classifier, support vector machine, neural networks and the like. A person skilled in the art will also appreciate that the Al module may be implemented as a set of software instructions, combination of software and hardware or any combination of the same.

[0010] Some of the typical tasks performed by Al systems are classification, clustering, regression etc. Majority of classification tasks depend upon labeled datasets; that is, the data sets are labelled manually in order for a neural network to learn the correlation between labels and data. This is known as supervised learning. Some of the typical applications of classifications are: face recognition, object identification, gesture recognition, voice recognition etc. Clustering or grouping is the detection of similarities in the inputs. The cluster learning techniques do not require labels to detect similarities. Learning without labels is called unsupervised learning. Unlabeled data is the majority of data in the world. One law of machine learning is: the more data an algorithm can train on, the more accurate it will be. Therefore, unsupervised learning models/algorithms has the potential to produce accurate models as training dataset size grows. [0011] As the Al module forms the core of the Al system, the module needs to be protected against attacks or undesirable modifications. The key idea here is to leverage the existing watermarking mechanism and tie it up with Distributed Ledger Technology (DLT) to generate proof of origin/ownership and integrity in a tamper-proof way. A person skilled in the art would understand that DLT are a consensus of digitized, decentralized & replicated append only digital data geographically spread across multiple locations. These decentralized, digitally managed ledgers have the capacity to distribute information with a high level of transparency and security. These distributed ledgers also act as a form of digital notary for a data providing immutable and indisputable information regarding the data.

[0012] Blockchain is one type of a distributed ledger. Blockchain organizes data into blocks, which are chained together in an append only mode. Once a transaction is initiated on blockchain, data is packaged in a “block”. The block of data contains the data and its metadata for example in case of a blockchain, the hash value of the preceding block of data. The block is sent to all members on the network linked by the blockchain for their consensus and approval. The consensus and approval between the members on the network can happen through a number of decentral consensus mechanisms. Once a consensus is given the block is added to the chain and this update is shared between the members on the network.

[0013] Figure 1 illustrates method steps (100) for checking ownership and integrity of an Al model using distributed ledger technology (DLT). The method step (100) by means of system comprising a plurality of processing nodes linked by a distributed ledger over a network and at least an Al model. Method step 101 comprises embedding a digital watermark in an Al model during training of the Al model using a first watermark data and its predefined output. This is accomplished by training the neural network model to learn the watermark by means a predefined label associated with a modified input. ¹

¹ Zhang, J., Gu, Z., Jang, J., Wu, H., Stoecklin, M.P., Huang, H. and Molloy, L, 2018, May. Protecting intellectual property of deep neural networks with watermarking. In Proceedings of the 2018 on Asia Conference on Computer and Communications Security (pp. 159-172). [0014] The method steps (100) are characterized by the following steps. Method step 102 comprises generating a full and selective checksums for the Al model. A checksum defined as a small-sized block of data derived from another block of digital data for the purpose of detecting errors that may have been introduced during its transmission or storage. A checksum is created by running an algorithm on a piece of data, which produces a checksum number, often called a hash. The hash can then be sent along with the original set of data. The receiver of the data can then use the hash to verify with a high probability that the data has not been altered or corrupted. In the context of this disclosure the data corresponds to the Al model to be registered on a distributed ledger.

[0015] The selective checksum may correspond to one of the many selection schemes, for example a scheme that generates checksum only for memory location that are multiples of a particular number. The training of the Al model is modified to generate the unique checksum of the new model using selective hashing techniques, to store on DLT along with model identification number. Method step 103 comprises registering the Al model on the distributed ledger (DL) by uploading full checksum, selective checksums, watermark data and at least the predefined output of the watermark data, a unique model ID is received upon registration. Method step 101-103 basically pertain to the registration of the Al model on the DL in a desired manner.

[0016] Once the model is registered on a DL, it’s ownership can be verified along with the determination of integrity of the Al model. These method steps are performed by any one of the processing nodes in the network linked by DLT. Method step 104 comprises receiving the Al model, model ID of the Al model and at least its watermark data as input. Method step 105 comprises checking for registration of Al model by matching received model ID with a stored model ID on the DL. Method step 106 comprises processing the watermark data to get an output and matching the processed output with the predefined output. Matching of model ID and matching of the processed output with the predefined output indicates positive acknowledgment of the ownership of the Al model.

[0017] Method step 107 comprises verifying the full and selective checksums of the Al model. The sequence of numbers in the full or selective checksums are held or generated by various processing nodes of the DL. Hence the checksum gives Al model a dependency on the DL. During verification if the full checksum verification fail, it means the integrity of the Al model is compromised. Positive acknowledgment of ownership followed by a full checksum verification indicates complete integrity of the Al model. The selective checksums are verified only if the full checksum verification fails.

[0018] Method step 108 comprises calculating an error for the Al model based on said selective checksum verification. A rate of error is calculated based on the percentage or portion of checksum that matches with the checksum generated for the Al model in method step 102. A minimum threshold of error is defined beyond which the Al model is said to be tampered. Error Threshold is decided based on model criticality and type of model. The calculation of error is done in many ways based on the output of the model. As an example, if watermark queries response is matched to that of original model response for >95% cases, the model is not considered tempered and does not have any impact on functionality. However, if model under verification produces response that of <90%, the model is considered as compromised and can result in high error. Final step 109 comprises determining the integrity of the Al model based on the calculated error. The rate of error decides a partial or no integrity of Al model suggestive of tampering of the Al model.

[0019] Figure 2 depicts the proposed system architecture for checking integrity of an Al model using distributed ledger technology (DLT) and a flow chart thereof. The proposed system architecture is configured to carry out steps elaborated in accordance with method steps 100. The system comprises a plurality of processing nodes linked by a distributed ledger over a network and at least an Al model embedded with a digital watermark during training of the Al model using a first watermark data and its predefined output. The Server- side here represents DLT implementation comprising the plurality of decentralized processing nodes. The system is configured to: Generate a full and selective checksums for the Al model; Register the Al model on the distributed ledger (DL) by uploading full checksum, selective checksums, watermark data and at least the predefined output of the watermark data, a unique model ID is received upon registration; receive the Al model, model ID of the Al model and at least its watermark data as input; check for registration of Al model by matching received model ID with a stored model ID on the DL; process the watermark data to get an output and matching the processed output with the predefined output; verify the full and selective checksum of the Al model; calculate an error for the Al model based on said selective checksum verification; determine the integrity of the Al model based on the calculated error. All in accordance with description provided for method steps 100.

[0020] The flow chart depicted in Figure 2 is explained by means of the following detailed step by step implementation of the method steps (100).

[0021] The key idea here is to leverage the state of the art watermarking mechanism and tie it up with DLT to generate proof of origin (provenance) in a tamper-proof way. On DLT, we store model metadata, model files and watermarking data as a whole. In case if DLT is unable to handle it, then off -chain storage mechanism can be used. The entire mechanism of verification can be implemented as a large smart contract or multiple smart contracts. The sequence described on server-side can be implemented as a one large smart contract or a plurality of smart contracts. For example, S302, 323, S332, S334 and S342 represents the smart contracts. Additionally, if the Al model is tampered with then generate an appropriate alert to reduce system operation to a safe level. If the model is completely replaced, but metadata is the same then it is indicative that the model is replaced in an unauthorized way and hence stop the system operation.

[0022] It must be understood that the disclosure in particular discloses methodology for checking integrity of an Al model using distributed ledger technology (DLT). While these methodologies describe only a series of steps to accomplish the objectives, these methodologies are implemented in a manner which may be a combination of hardware, software and a combination thereof. Further the methodologies are not specific to any particular processing node of the DLT. Conventional techniques used to prove ownership of the Al model requires us to provide watermarking data and its corresponding label making it vulnerable to an adversary even in case of verification. Using the above described method steps (100) the verification process can made to be hidden and undisputable.

[0023] It must be understood that the embodiments explained in the above detailed description are only illustrative and do not limit the scope of this invention. Any modification to the method for checking integrity of an Al model using distributed ledger technology (DLT) and the system thereof are envisaged and form a part of this invention. The scope of this invention is limited only by the claims.