Patent Publication Number: US-11379472-B2

Title: Schema-based pruning of blockchain data

Description:
BACKGROUND 
     A centralized platform stores and maintains data in a single location. This location is often a central computer, for example, a cloud computing environment, a web server, a mainframe computer, or the like. Information stored on a centralized platform is typically accessible from multiple different points. Multiple users or client workstations can work simultaneously on the centralized platform, for example, based on a client/server configuration. A centralized platform is easy to manage, maintain, and control, especially for purposes of security because of its single location. Within a centralized platform, data redundancy is minimized as a single storing place of all data also implies that a given set of data only has one primary record. 
     SUMMARY 
     One example embodiment provides an apparatus that includes a network interface configured to receive, from a client, a pruned data structure that comprises a plurality of fields and a plurality of hash values, respectively, and processor configured to one or more of identify a schema associated with the pruned data structure, determine whether the pruned data structure is a valid based on the plurality of fields in the data structure and the identified schema associated with the client, and in response to a determination that the pruned data structure is valid, commit the pruned data structure to a blockchain. 
     Another example embodiment provides a method that includes one or more of receiving, from a client, a pruned data structure that comprises a plurality of fields and a plurality of hash values, respectively, identifying a schema associated with the pruned data structure, determining whether the pruned data structure is a valid based on the plurality of fields in the data structure and the identified schema associated with the client, and in response to a determination that the pruned data structure is valid, committing the pruned data structure to a blockchain. 
     A further example embodiment provides a non-transitory computer-readable medium comprising instructions, that when read by a processor, cause the processor to perform one or more of receiving, from a client, a pruned data structure that comprises a plurality of fields and a plurality of hash values, respectively, identifying a schema associated with the pruned data structure, determining whether the pruned data structure is a valid based on the plurality of fields in the data structure and the identified schema associated with the client, and in response to a determination that the pruned data structure is valid, committing the pruned data structure to a blockchain. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a diagram illustrating a process of a client submitting a pruned data structure to a blockchain according to example embodiments. 
         FIG. 1B  is a diagram illustrating a process of a blockchain peer validating a schema of the pruned data structure according to example embodiments. 
         FIG. 1C  is a diagram illustrating a process of validating a previously stored pruned data structure according to example embodiments. 
         FIG. 2A  is a diagram illustrating an example blockchain architecture configuration, according to example embodiments. 
         FIG. 2B  is a diagram illustrating a blockchain transactional flow among nodes, according to example embodiments. 
         FIG. 3A  is a diagram illustrating a permissioned network, according to example embodiments. 
         FIG. 3B  is a diagram illustrating another permissioned network, according to example embodiments. 
         FIG. 3C  is a diagram illustrating a permissionless network, according to example embodiments. 
         FIGS. 4A-4B  are diagrams illustrating processes of pruning a data payload according to various schemas according to example embodiments. 
         FIG. 5  is a diagram illustrating a method of validating a pruned data structure via a blockchain according to example embodiments. 
         FIG. 6A  is a diagram illustrating an example system configured to perform one or more operations described herein, according to example embodiments. 
         FIG. 6B  is a diagram illustrating another example system configured to perform one or more operations described herein, according to example embodiments. 
         FIG. 6C  is a diagram illustrating a further example system configured to utilize a smart contract, according to example embodiments. 
         FIG. 6D  is a diagram illustrating yet another example system configured to utilize a blockchain, according to example embodiments. 
         FIG. 7A  is a diagram illustrating a process of a new block being added to a distributed ledger, according to example embodiments. 
         FIG. 7B  is a diagram illustrating data contents of a new data block, according to example embodiments. 
         FIG. 7C  is a diagram illustrating a blockchain for digital content, according to example embodiments. 
         FIG. 7D  is a diagram illustrating a block which may represent the structure of blocks in the blockchain, according to example embodiments. 
         FIG. 8A  is a diagram illustrating an example blockchain which stores machine learning (artificial intelligence) data, according to example embodiments. 
         FIG. 8B  is a diagram illustrating an example quantum-secure blockchain, according to example embodiments. 
         FIG. 9  is a diagram illustrating an example system that supports one or more of the example embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     It will be readily understood that the instant components, as generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of at least one of a method, apparatus, non-transitory computer readable medium and system, as represented in the attached figures, is not intended to limit the scope of the application as claimed but is merely representative of selected embodiments. 
     The instant features, structures, or characteristics as described throughout this specification may be combined or removed in any suitable manner in one or more embodiments. For example, the usage of the phrases “example embodiments”, “some embodiments”, or other similar language, throughout this specification refers to the fact that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment. Thus, appearances of the phrases “example embodiments”, “in some embodiments”, “in other embodiments”, or other similar language, throughout this specification do not necessarily all refer to the same group of embodiments, and the described features, structures, or characteristics may be combined or removed in any suitable manner in one or more embodiments. Further, in the diagrams, any connection between elements can permit one-way and/or two-way communication even if the depicted connection is a one-way or two-way arrow. Also, any device depicted in the drawings can be a different device. For example, if a mobile device is shown sending information, a wired device could also be used to send the information. 
     In addition, while the term “message” may have been used in the description of embodiments, the application may be applied to many types of networks and data. Furthermore, while certain types of connections, messages, and signaling may be depicted in exemplary embodiments, the application is not limited to a certain type of connection, message, and signaling. 
     Example embodiments provide methods, systems, components, non-transitory computer readable media, devices, and/or networks, which are directed to storing and validating a pruned data structure which is stored to a blockchain. 
     According to various aspects, a data item, for example, a video, an audio, a document, a file, or the like, can be pruned according to a predefined schema. The pruning process replaces values of data with hash values, while leaving identifiers of the data such that the content within the data item can still be validated by the blockchain. As a simple example, document may be stored on the blockchain. Prior to storing the document, a client may decompose the document into a plurality of fields. For example, the document may include a header, a drawing, a description, and a timestamp which are each assigned their fields within the pruned data structure. However, rather than store the actual content, the pruned data structure may store hash values of the respective pieces of content (e.g., hashes of the header, drawing, description, timestamp, etc.). A hash value may have predefined size (e.g., 128 bits, 256 bits, etc.) that is significantly smaller than the original content. As a result, the amount of data that is stored on the blockchain can be significantly reduced (e.g., collapsed, etc.) by replacing actual content with hash values. Furthermore, the data structure may be formatted according to a predefined schema (e.g., the fields) that the schema of the data can be verified by the blockchain. 
     When a blockchain peer receives the pruned data structure, the blockchain peer can verify the schema of the pruned data structure matches a predefined schema associated with the client, the data, the blockchain, etc. Furthermore, the blockchain peer may create a hash value by generating a hash tree representing the pruned data structure. In this example, the fields may be the leaves of the hash tree, which are rolled up into a root hash. The resulting root hash may be all that is stored to the blockchain. 
     When the client desires to prove existence of the data item on the blockchain, the client can recreate the pruned data structure, and recreate the root hash as performed by the blockchain. The client can also request the previously stored root hash from the blockchain and compare the recreated root hash to the previously stored root hash to verify that the data item was previously stored to the blockchain. 
     The schema may be predefined by a client, a data provider, a blockchain, or the like. The schema may be selected from among a plurality of schemas that are accessible to the blockchain peers. For example, the different schemas may be stored in a registry on the blockchain ledger. The schema may define how data should be structured and what is required to be included and what is optional. Examples of schemas include schemas provided by YAML Ain&#39;t Markup Language (YAML), JavaScript Object Notation (JSON), and the like, which can describe any structure possible. The schema also identifies what specific pieces of data can be collapsed (e.g., represented by a hash, a digest, etc.), instead of including the entire data. In the example embodiments, the client may generate the pruned data structure in a JSON schema, a YAML schema, or the like, which identifies the fields and whether the fields should be hashed or not. The blockchain peers, with knowledge of the schema, can validate that a piece of structured data is compliant with the schema. 
     In one embodiment this application utilizes a decentralized database (such as a blockchain) that is a distributed storage system, which includes multiple nodes that communicate with each other. The decentralized database includes an append-only immutable data structure resembling a distributed ledger capable of maintaining records between mutually untrusted parties. The untrusted parties are referred to herein as peers or peer nodes. Each peer maintains a copy of the database records and no single peer can modify the database records without a consensus being reached among the distributed peers. For example, the peers may execute a consensus protocol to validate blockchain storage transactions, group the storage transactions into blocks, and build a hash chain over the blocks. This process forms the ledger by ordering the storage transactions, as is necessary, for consistency. In various embodiments, a permissioned and/or a permissionless blockchain can be used. In a public or permission-less blockchain, anyone can participate without a specific identity. Public blockchains can involve native cryptocurrency and use consensus based on various protocols such as Proof of Work (PoW). On the other hand, a permissioned blockchain database provides secure interactions among a group of entities which share a common goal but which do not fully trust one another, such as businesses that exchange funds, goods, information, and the like. 
     This application can utilize a blockchain that operates arbitrary, programmable logic, tailored to a decentralized storage scheme and referred to as “smart contracts” or “chaincodes.” In some cases, specialized chaincodes may exist for management functions and parameters which are referred to as system chaincode. The application can further utilize smart contracts that are trusted distributed applications which leverage tamper-proof properties of the blockchain database and an underlying agreement between nodes, which is referred to as an endorsement or endorsement policy. Blockchain transactions associated with this application can be “endorsed” before being committed to the blockchain while transactions, which are not endorsed, are disregarded. An endorsement policy allows chaincode to specify endorsers for a transaction in the form of a set of peer nodes that are necessary for endorsement. When a client sends the transaction to the peers specified in the endorsement policy, the transaction is executed to validate the transaction. After validation, the transactions enter an ordering phase in which a consensus protocol is used to produce an ordered sequence of endorsed transactions grouped into blocks. 
     This application can utilize nodes that are the communication entities of the blockchain system. A “node” may perform a logical function in the sense that multiple nodes of different types can run on the same physical server. Nodes are grouped in trust domains and are associated with logical entities that control them in various ways. Nodes may include different types, such as a client or submitting-client node which submits a transaction-invocation to an endorser (e.g., peer), and broadcasts transaction-proposals to an ordering service (e.g., ordering node). Another type of node is a peer node which can receive client submitted transactions, commit the transactions and maintain a state and a copy of the ledger of blockchain transactions. Peers can also have the role of an endorser, although it is not a requirement. An ordering-service-node or orderer is a node running the communication service for all nodes, and which implements a delivery guarantee, such as a broadcast to each of the peer nodes in the system when committing transactions and modifying a world state of the blockchain, which is another name for the initial blockchain transaction which normally includes control and setup information. 
     This application can utilize a ledger that is a sequenced, tamper-resistant record of all state transitions of a blockchain. State transitions may result from chaincode invocations (i.e., transactions) submitted by participating parties (e.g., client nodes, ordering nodes, endorser nodes, peer nodes, etc.). Each participating party (such as a peer node) can maintain a copy of the ledger. A transaction may result in a set of asset key-value pairs being committed to the ledger as one or more operands, such as creates, updates, deletes, and the like. The ledger includes a blockchain (also referred to as a chain) which is used to store an immutable, sequenced record in blocks. The ledger also includes a state database which maintains a current state of the blockchain. 
     This application can utilize a chain that is a transaction log which is structured as hash-linked blocks, and each block contains a sequence of N transactions where N is equal to or greater than one. The block header includes a hash of the block&#39;s transactions, as well as a hash of the prior block&#39;s header. In this way, all transactions on the ledger may be sequenced and cryptographically linked together. Accordingly, it is not possible to tamper with the ledger data without breaking the hash links. A hash of a most recently added blockchain block represents every transaction on the chain that has come before it, making it possible to ensure that all peer nodes are in a consistent and trusted state. The chain may be stored on a peer node file system (i.e., local, attached storage, cloud, etc.), efficiently supporting the append-only nature of the blockchain workload. 
     The current state of the immutable ledger represents the latest values for all keys that are included in the chain transaction log. Since the current state represents the latest key values known to a channel, it is sometimes referred to as a world state. Chaincode invocations execute transactions against the current state data of the ledger. To make these chaincode interactions efficient, the latest values of the keys may be stored in a state database. The state database may be simply an indexed view into the chain&#39;s transaction log, it can therefore be regenerated from the chain at any time. The state database may automatically be recovered (or generated if needed) upon peer node startup, and before transactions are accepted. 
     Some of the benefits provided by the example embodiments include a system which enables a client to prove that a particular piece of data was stored to the blockchain without the actual state of the data (including any sensitive information) being stored on the blockchain. For example, a data item (e.g., a video, a file, a document, etc.) may be decomposed into a pruned data structure that includes a plurality of fields (e.g., objects, arrays, null values, Booleans, etc.) which have values stored therein. The fields used may be based on a predefined schema that is stored and made accessible to the blockchain peers. Some or all of the data values may be hashed to reduce/collapse the data being stored such that only a digest of the data is stored in hash form. A blockchain can subsequently verify that the pruned data structure satisfies the schema without actually having to validate the underlying data. Thus, storage on the blockchain can be significantly reduced, while proof of storage of a data item can still be provided. Furthermore, sensitive content within the data item (that has been pruned) is not disclosed to the blockchain or to any other parties outside the client. 
       FIG. 1A  illustrates a process  100 A of a client  110  submitting a pruned data structure  120  to a blockchain  130  according to example embodiments. Referring to  FIG. 1A , the client  110  may have a data item (e.g., a payload) such as a video, a data set, an audio, a data file, a data table, a document, or the like. In this case, the client  110  may decompose the data item into a pruned data structure  120  in which the payload of data is converted into a series of fields and values that are stored in the fields. The pruned data structure  120  may be formatted based on a predefined schema that is available to the blockchain  130 . Examples of different types of schemas are shown and described with respect to  FIGS. 4A and 4B . 
     The fields may be defined by the schema and may include strings, numbers, arrays, Booleans, objects with key/value pairs, nulls, and the like. Within the fields may be values that have been hashed (or not hashed). That is, some of the values, all of the values, etc., may be hashed to collapse the data within the pruned data structure to thereby reduce the amount of data that is submitted to the blockchain  130 . Each data field may also include an identifier that describes what content (i.e., the value) that is stored within each field. 
     As an example, a file may represent a document with six sections of content therein. In this example, the document may be converted by the client into the pruned data structure  120  that includes an object with six key/value pairs therein that represent the six content sections of the document. For example, field A may represent a header, field B may represent a first paragraph, field C may represent a second paragraph, field D may represent a conclusion, field E may represent an encryption scheme used on the document, and field F may be a timestamp at which the document is created. Thus, the document may be converted into the pruned data structure  120  that that still identifies information about the document including the different sections without including the actual document content. Instead, hashes of the document content may be stored in fields A, B, C, and D. It should be appreciated that any type of data item may be stored, not just documents. For example, videos, audios, data sets (e.g., machine learning, etc.), tables, and the like. Also, the schema may define what type of storage types should be included in the pruned data structure. 
       FIG. 1B  illustrates a process  100 B of a blockchain peer  132  validating a schema of the pruned data structure according to example embodiments. In this example, the blockchain peer  132  is one of many possible blockchain peers that may be include a copy of and manage the blockchain  130  shown in  FIG. 1A . Here, the client  110  may submit the pruned data structure  120  in the form of a blockchain transaction. The blockchain network may perform an endorsement process such as shown and described with respect to  FIG. 2B . Prior to committing the pruned data structure  120  to the blockchain  130 , the blockchain peer  132  may verify that a schema of the pruned data structure  120  complies with a predefined schema that is associated with one or more of the client  110 , the pruned data structure  120 , the blockchain  130 , or the like. In this example, an identifier of the schema may be provided from the client  110  when providing the pruned data structure  120 . As another example, the blockchain peer  132  may identify the schema from a schema registry  134  based on an identifier of the client  110 , the pruned data  120 , or any other information. 
     The blockchain peer  132  may identify the predefined schema associated with the pruned data  120  from the schema registry  134 , and compare the identified schema to the content within the pruned data structure  120  to ensure that the fields (data values) within the pruned data structure  120  comply with the identified schema. If the pruned data structure  120  does not comply with the identified schema, the pruned data structure  120  can be denied storage on the blockchain  130 . However, if the pruned data structure  120  is validated with respect to the identified schema, the pruned data structure  120  may be stored to the blockchain  130 . 
     In one example, the blockchain peer  132  may arrange the fields A-F within the pruned data structure in a hash tree  140  as shown in  FIG. 1B . Here, the values within each of the fields A-F may be assigned to nodes  141 - 146  of the hash tree  140 , respectively. The result is a series of values assigned to leaf nodes  141 - 146  of the hash tree  140  which may be rolled up to create a root hash value. For example, the values may be rolled-up by hashing adjacent pairs of leaf nodes  141 - 146  together to create a set of three intermediate nodes (AB, CD, and EF). Furthermore, two intermediate nodes AB and CD may be rolled up into a hash ABCD which is then rolled-up with the intermediate node hash EF to create a root hash  147 . The root hash  147  is a single hash value that represents the entire pruned data structure  120 . Here, the blockchain peer  132  can store the root hash  147  as the representative value of the pruned data structure  120  to the blockchain  130 . It should also be appreciated that the pruned data structure  120  may be stored as is on the blockchain, or other hashing mechanisms may be applied. 
       FIG. 1C  illustrates a process  100 C of validating a previously stored pruned data structure according to example embodiments. When the client  110  (or some other entity with access to the blockchain) desires to prove that the data item was previously stored to the blockchain  130 , the client  110  can decompose the original data item and recreate the pruned data structure  120 . The client  110  can then use the same hash function (e.g., the hash tree  140 , etc.) used by the blockchain peer  132  to recreate the root hash  147 . The client  110  can also request the previous root hash already stored on the blockchain  130  from the blockchain peer  132 . In response, the blockchain peer  132  can provide the previous root hash. The client  110  can compare the recreated root hash and the previously stored root hash to verify that they are the same. If they are the same, the data item is the same. 
       FIG. 2A  illustrates a blockchain architecture configuration  200 , according to example embodiments. Referring to  FIG. 2A , the blockchain architecture  200  may include certain blockchain elements, for example, a group of blockchain nodes  202 . The blockchain nodes  202  may include one or more nodes  204 - 210  (these four nodes are depicted by example only). These nodes participate in a number of activities, such as blockchain transaction addition and validation process (consensus). One or more of the blockchain nodes  204 - 210  may endorse transactions based on endorsement policy and may provide an ordering service for all blockchain nodes in the architecture  200 . A blockchain node may initiate a blockchain authentication and seek to write to a blockchain immutable ledger stored in blockchain layer  216 , a copy of which may also be stored on the underpinning physical infrastructure  214 . The blockchain configuration may include one or more applications  224  which are linked to application programming interfaces (APIs)  222  to access and execute stored program/application code  220  (e.g., chaincode, smart contracts, etc.) which can be created according to a customized configuration sought by participants and can maintain their own state, control their own assets, and receive external information. This can be deployed as a transaction and installed, via appending to the distributed ledger, on all blockchain nodes  204 - 210 . 
     The blockchain base or platform  212  may include various layers of blockchain data, services (e.g., cryptographic trust services, virtual execution environment, etc.), and underpinning physical computer infrastructure that may be used to receive and store new transactions and provide access to auditors which are seeking to access data entries. The blockchain layer  216  may expose an interface that provides access to the virtual execution environment necessary to process the program code and engage the physical infrastructure  214 . Cryptographic trust services  218  may be used to verify transactions such as asset exchange transactions and keep information private. 
     The blockchain architecture configuration of  FIG. 2A  may process and execute program/application code  220  via one or more interfaces exposed, and services provided, by blockchain platform  212 . The code  220  may control blockchain assets. For example, the code  220  can store and transfer data, and may be executed by nodes  204 - 210  in the form of a smart contract and associated chaincode with conditions or other code elements subject to its execution. As a non-limiting example, smart contracts may be created to execute reminders, updates, and/or other notifications subject to the changes, updates, etc. The smart contracts can themselves be used to identify rules associated with authorization and access requirements and usage of the ledger. For example, the smart contract (or chaincode executing the logic of the smart contract) may read blockchain data  226  which may be processed by one or more processing entities (e.g., virtual machines) included in the blockchain layer  216  to generate results  228  including alerts, determining liability, and the like, within a complex service scenario. The physical infrastructure  214  may be utilized to retrieve any of the data or information described herein. 
     A smart contract may be created via a high-level application and programming language, and then written to a block in the blockchain. The smart contract may include executable code which is registered, stored, and/or replicated with a blockchain (e.g., distributed network of blockchain peers). A transaction is an execution of the smart contract logic which can be performed in response to conditions associated with the smart contract being satisfied. The executing of the smart contract may trigger a trusted modification(s) to a state of a digital blockchain ledger. The modification(s) to the blockchain ledger caused by the smart contract execution may be automatically replicated throughout the distributed network of blockchain peers through one or more consensus protocols. 
     The smart contract may write data to the blockchain in the format of key-value pairs. Furthermore, the smart contract code can read the values stored in a blockchain and use them in application operations. The smart contract code can write the output of various logic operations into one or more blocks within the blockchain. The code may be used to create a temporary data structure in a virtual machine or other computing platform. Data written to the blockchain can be public and/or can be encrypted and maintained as private. The temporary data that is used/generated by the smart contract is held in memory by the supplied execution environment, then deleted once the data needed for the blockchain is identified. 
     A chaincode may include the code interpretation (e.g., the logic) of a smart contract. For example, the chaincode may include a packaged and deployable version of the logic within the smart contract. As described herein, the chaincode may be program code deployed on a computing network, where it is executed and validated by chain validators together during a consensus process. The chaincode may receive a hash and retrieve from the blockchain a hash associated with the data template created by use of a previously stored feature extractor. If the hashes of the hash identifier and the hash created from the stored identifier template data match, then the chaincode sends an authorization key to the requested service. The chaincode may write to the blockchain data associated with the cryptographic details. 
       FIG. 2B  illustrates an example of a blockchain transactional flow  250  between nodes of the blockchain in accordance with an example embodiment. Referring to  FIG. 2B , the transaction flow may include a client node  260  transmitting a transaction proposal  291  to an endorsing peer node  281 . The endorsing peer  281  may verify the client signature and execute a chaincode function to initiate the transaction. The output may include the chaincode results, a set of key/value versions that were read in the chaincode (read set), and the set of keys/values that were written in chaincode (write set). Here, the endorsing peer  281  may determine whether or not to endorse the transaction proposal. The proposal response  292  is sent back to the client  260  along with an endorsement signature, if approved. The client  260  assembles the endorsements into a transaction payload  293  and broadcasts it to an ordering service node  284 . The ordering service node  284  then delivers ordered transactions as blocks to all peers  281 - 283  on a channel. Before committal to the blockchain, each peer  281 - 283  may validate the transaction. For example, the peers may check the endorsement policy to ensure that the correct allotment of the specified peers have signed the results and authenticated the signatures against the transaction payload  293 . 
     Referring again to  FIG. 2B , the client node initiates the transaction  291  by constructing and sending a request to the peer node  281 , which is an endorser. The client  260  may include an application leveraging a supported software development kit (SDK), which utilizes an available API to generate a transaction proposal. The proposal is a request to invoke a chaincode function so that data can be read and/or written to the ledger (i.e., write new key value pairs for the assets). The SDK may serve as a shim to package the transaction proposal into a properly architected format (e.g., protocol buffer over a remote procedure call (RPC)) and take the client&#39;s cryptographic credentials to produce a unique signature for the transaction proposal. 
     In response, the endorsing peer node  281  may verify (a) that the transaction proposal is well formed, (b) the transaction has not been submitted already in the past (replay-attack protection), (c) the signature is valid, and (d) that the submitter (client  260 , in the example) is properly authorized to perform the proposed operation on that channel. The endorsing peer node  281  may take the transaction proposal inputs as arguments to the invoked chaincode function. The chaincode is then executed against a current state database to produce transaction results including a response value, read set, and write set. However, no updates are made to the ledger at this point. In  292 , the set of values, along with the endorsing peer node&#39;s  281  signature is passed back as a proposal response  292  to the SDK of the client  260  which parses the payload for the application to consume. 
     In response, the application of the client  260  inspects/verifies the signatures of the endorsing peers and compares the proposal responses to determine if the proposal response is the same. If the chaincode only queried the ledger, the application would inspect the query response and would typically not submit the transaction to the ordering node service  284 . If the client application intends to submit the transaction to the ordering node service  284  to update the ledger, the application determines if the specified endorsement policy has been fulfilled before submitting (i.e., did all peer nodes necessary for the transaction endorse the transaction). Here, the client may include only one of multiple parties to the transaction. In this case, each client may have their own endorsing node, and each endorsing node will need to endorse the transaction. The architecture is such that even if an application selects not to inspect responses or otherwise forwards an unendorsed transaction, the endorsement policy will still be enforced by peers and upheld at the commit validation phase. 
     After successful inspection, in step  293  the client  260  assembles endorsements into a transaction proposal and broadcasts the transaction proposal and response within a transaction message to the ordering node  284 . The transaction may contain the read/write sets, the endorsing peer signatures and a channel ID. The ordering node  284  does not need to inspect the entire content of a transaction in order to perform its operation, instead the ordering node  284  may simply receive transactions from all channels in the network, order them chronologically by channel, and create blocks of transactions per channel. 
     The blocks are delivered from the ordering node  284  to all peer nodes  281 - 283  on the channel. The data section within the block may be validated to ensure an endorsement policy is fulfilled and to ensure that there have been no changes to ledger state for read set variables since the read set was generated by the transaction execution. Furthermore, in step  295  each peer node  281 - 283  appends the block to the channel&#39;s chain, and for each valid transaction the write sets are committed to current state database. An event may be emitted, to notify the client application that the transaction (invocation) has been immutably appended to the chain, as well as to notify whether the transaction was validated or invalidated. 
       FIG. 3A  illustrates an example of a permissioned blockchain network  300 , which features a distributed, decentralized peer-to-peer architecture. In this example, a blockchain user  302  may initiate a transaction to the permissioned blockchain  304 . In this example, the transaction can be a deploy, invoke, or query, and may be issued through a client-side application leveraging an SDK, directly through an API, etc. Networks may provide access to a regulator  306 , such as an auditor. A blockchain network operator  308  manages member permissions, such as enrolling the regulator  306  as an “auditor” and the blockchain user  302  as a “client”. An auditor could be restricted only to querying the ledger whereas a client could be authorized to deploy, invoke, and query certain types of chaincode. 
     A blockchain developer  310  can write chaincode and client-side applications. The blockchain developer  310  can deploy chaincode directly to the network through an interface. To include credentials from a traditional data source  312  in chaincode, the developer  310  could use an out-of-band connection to access the data. In this example, the blockchain user  302  connects to the permissioned blockchain  304  through a peer node  314 . Before proceeding with any transactions, the peer node  314  retrieves the user&#39;s enrollment and transaction certificates from a certificate authority  316 , which manages user roles and permissions. In some cases, blockchain users must possess these digital certificates in order to transact on the permissioned blockchain  304 . Meanwhile, a user attempting to utilize chaincode may be required to verify their credentials on the traditional data source  312 . To confirm the user&#39;s authorization, chaincode can use an out-of-band connection to this data through a traditional processing platform  318 . 
       FIG. 3B  illustrates another example of a permissioned blockchain network  320 , which features a distributed, decentralized peer-to-peer architecture. In this example, a blockchain user  322  may submit a transaction to the permissioned blockchain  324 . In this example, the transaction can be a deploy, invoke, or query, and may be issued through a client-side application leveraging an SDK, directly through an API, etc. Networks may provide access to a regulator  326 , such as an auditor. A blockchain network operator  328  manages member permissions, such as enrolling the regulator  326  as an “auditor” and the blockchain user  322  as a “client”. An auditor could be restricted only to querying the ledger whereas a client could be authorized to deploy, invoke, and query certain types of chaincode. 
     A blockchain developer  330  writes chaincode and client-side applications. The blockchain developer  330  can deploy chaincode directly to the network through an interface. To include credentials from a traditional data source  332  in chaincode, the developer  330  could use an out-of-band connection to access the data. In this example, the blockchain user  322  connects to the network through a peer node  334 . Before proceeding with any transactions, the peer node  334  retrieves the user&#39;s enrollment and transaction certificates from the certificate authority  336 . In some cases, blockchain users must possess these digital certificates in order to transact on the permissioned blockchain  324 . Meanwhile, a user attempting to utilize chaincode may be required to verify their credentials on the traditional data source  332 . To confirm the user&#39;s authorization, chaincode can use an out-of-band connection to this data through a traditional processing platform  338 . 
     In some embodiments, the blockchain herein may be a permissionless blockchain. In contrast with permissioned blockchains which require permission to join, anyone can join a permissionless blockchain. For example, to join a permissionless blockchain a user may create a personal address and begin interacting with the network, by submitting transactions, and hence adding entries to the ledger. Additionally, all parties have the choice of running a node on the system and employing the mining protocols to help verify transactions. 
       FIG. 3C  illustrates a process  350  of a transaction being processed by a permissionless blockchain  352  including a plurality of nodes  354 . A sender  356  desires to send payment or some other form of value (e.g., a deed, medical records, a contract, a good, a service, or any other asset that can be encapsulated in a digital record) to a recipient  358  via the permissionless blockchain  352 . In one embodiment, each of the sender device  356  and the recipient device  358  may have digital wallets (associated with the blockchain  352 ) that provide user interface controls and a display of transaction parameters. In response, the transaction is broadcast throughout the blockchain  352  to the nodes  354 . Depending on the blockchain&#39;s  352  network parameters the nodes verify  360  the transaction based on rules (which may be pre-defined or dynamically allocated) established by the permissionless blockchain  352  creators. For example, this may include verifying identities of the parties involved, etc. The transaction may be verified immediately or it may be placed in a queue with other transactions and the nodes  354  determine if the transactions are valid based on a set of network rules. 
     In structure  362 , valid transactions are formed into a block and sealed with a lock (hash). This process may be performed by mining nodes among the nodes  354 . Mining nodes may utilize additional software specifically for mining and creating blocks for the permissionless blockchain  352 . Each block may be identified by a hash (e.g., 256 bit number, etc.) created using an algorithm agreed upon by the network. Each block may include a header, a pointer or reference to a hash of a previous block&#39;s header in the chain, and a group of valid transactions. The reference to the previous block&#39;s hash is associated with the creation of the secure independent chain of blocks. 
     Before blocks can be added to the blockchain, the blocks must be validated. Validation for the permissionless blockchain  352  may include a proof-of-work (PoW) which is a solution to a puzzle derived from the block&#39;s header. Although not shown in the example of  FIG. 3C , another process for validating a block is proof-of-stake. Unlike the proof-of-work, where the algorithm rewards miners who solve mathematical problems, with the proof of stake, a creator of a new block is chosen in a deterministic way, depending on its wealth, also defined as “stake.” Then, a similar proof is performed by the selected/chosen node. 
     With mining  364 , nodes try to solve the block by making incremental changes to one variable until the solution satisfies a network-wide target. This creates the PoW thereby ensuring correct answers. In other words, a potential solution must prove that computing resources were drained in solving the problem. In some types of permissionless blockchains, miners may be rewarded with value (e.g., coins, etc.) for correctly mining a block. 
     Here, the PoW process, alongside the chaining of blocks, makes modifications of the blockchain extremely difficult, as an attacker must modify all subsequent blocks in order for the modifications of one block to be accepted. Furthermore, as new blocks are mined, the difficulty of modifying a block increases, and the number of subsequent blocks increases. With distribution  366 , the successfully validated block is distributed through the permissionless blockchain  352  and all nodes  354  add the block to a majority chain which is the permissionless blockchain&#39;s  352  auditable ledger. Furthermore, the value in the transaction submitted by the sender  356  is deposited or otherwise transferred to the digital wallet of the recipient device  358 . 
       FIGS. 4A-4B  illustrate processes  400 A and  400 B of pruning a data payload according to various schemas according to example embodiments. For example, the processes  400 A and  400 B may be performed by a client or other entity prior to submitting the pruned data for storage on a blockchain. Referring to  FIG. 4A , a data payload includes a video file  410  composed of a plurality of scenes. Each scene is a subset of video frames. The video file  410  is encrypted according to a predefined encryption type. 
     To create a pruned data structure  420  for the video file  410 , the client may break-up the video file  410  into a plurality of scenes (e.g., scenes A-N, and create hash values of the scenes. Here, the pruned data structure  420  may include an identifier  422  of a scene and a value  424  (hash content) of the scene. Likewise, the encryption scheme used by the video file may be identified with an identifier  426  and field filled with a value  428 . Here, the value is not hashed. Whether the values are to be hashed or not may be identified within the predefined schema. 
       FIG. 4B  illustrates an example of payload that includes machine learning training data  430  that is used to train a machine learning model (e.g., linear, regression, classification, etc.). The machine learning training may require many different iterations of training where each iteration uses a different training data set. After each iteration, the parameters of the machine learning algorithm may change. In this case, the client can decompose the machine learning training data  430  into smaller sets of data for each iteration. For example, each iteration may have a data set value  444  which is a hash of the actual training data set using during that iteration, and a parameter value  448  which is a hash of the parameters of the machine learning model after that round of training. Also, identifiers  442  and  446  may identify the fields storing the hash values  444  and  448 , respectively. 
       FIG. 5  illustrates a method  500  of validating a pruned data structure via a blockchain according to example embodiments. As a non-limiting example, the method  500  may be performed by a blockchain peer that manages a blockchain ledger, and the like. Referring to  FIG. 5 , in  510 , the method may include receiving, from a client, a pruned data structure that comprises a plurality of fields and a plurality of hash values, respectively. In some embodiments, the pruned data structure may include the plurality of fields filled with the plurality of hash values, where each field includes an identifier of the content that is included in the field. For example, a field name may describe what value is stored in the field and may be placed adjacent to the field. Examples of field types include objects, arrays, numbers, strings, Booleans, null values, and the like. In some embodiments, the fields may be arranged in a predetermined order (e.g., field  1  may be above field  2 , etc.). 
     In  520 , the method may include identifying a schema associated with the pruned data structure. In some embodiments, the identifying may include identifying the schema based on a data value included with the pruned data structure from the client. Here, the schema defines which fields must be present within the pruned data structure. In some cases, the schema may also define what values must be hashed, what values do not need to be hashed, an order in which the fields/values are arranged, and the like. 
     In  530 , the method may include determining whether the pruned data structure is a valid based on the plurality of fields in the data structure and the identified schema associated with the client. In response to a determination that the pruned data structure is valid, in  540  the method may include committing the pruned data structure to a blockchain. In some embodiments, the committing may include generating a sequence of hash values in a hierarchical tree structure, and hashing the sequence to generate a root hash value which is stored on the blockchain. 
     In some embodiments, the determining may include validating the schema based on a schema stored in a registry of schemas stored on the blockchain. In some embodiments, the determining may include verifying that fields required by the identified schema are included in the pruned data structure to determine whether the pruned data structure is valid. In some embodiments, the determining may include determining, via a chaincode of the blockchain, whether the pruned data structure is valid based on the identified schema. 
       FIG. 6A  illustrates an example system  600  that includes a physical infrastructure  610  configured to perform various operations according to example embodiments. Referring to  FIG. 6A , the physical infrastructure  610  includes a module  612  and a module  614 . The module  614  includes a blockchain  620  and a smart contract  630  (which may reside on the blockchain  620 ), that may execute any of the operational steps  608  (in module  612 ) included in any of the example embodiments. The steps/operations  608  may include one or more of the embodiments described or depicted and may represent output or written information that is written or read from one or more smart contracts  630  and/or blockchains  620 . The physical infrastructure  610 , the module  612 , and the module  614  may include one or more computers, servers, processors, memories, and/or wireless communication devices. Further, the module  612  and the module  614  may be a same module. 
       FIG. 6B  illustrates another example system  640  configured to perform various operations according to example embodiments. Referring to  FIG. 6B , the system  640  includes a module  612  and a module  614 . The module  614  includes a blockchain  620  and a smart contract  630  (which may reside on the blockchain  620 ), that may execute any of the operational steps  608  (in module  612 ) included in any of the example embodiments. The steps/operations  608  may include one or more of the embodiments described or depicted and may represent output or written information that is written or read from one or more smart contracts  630  and/or blockchains  620 . The physical infrastructure  610 , the module  612 , and the module  614  may include one or more computers, servers, processors, memories, and/or wireless communication devices. Further, the module  612  and the module  614  may be a same module. 
       FIG. 6C  illustrates an example system configured to utilize a smart contract configuration among contracting parties and a mediating server configured to enforce the smart contract terms on the blockchain according to example embodiments. Referring to  FIG. 6C , the configuration  650  may represent a communication session, an asset transfer session or a process or procedure that is driven by a smart contract  630  which explicitly identifies one or more user devices  652  and/or  656 . The execution, operations and results of the smart contract execution may be managed by a server  654 . Content of the smart contract  630  may require digital signatures by one or more of the entities  652  and  656  which are parties to the smart contract transaction. The results of the smart contract execution may be written to a blockchain  620  as a blockchain transaction. The smart contract  630  resides on the blockchain  620  which may reside on one or more computers, servers, processors, memories, and/or wireless communication devices. 
       FIG. 6D  illustrates a system  660  including a blockchain, according to example embodiments. Referring to the example of  FIG. 6D , an application programming interface (API) gateway  662  provides a common interface for accessing blockchain logic (e.g., smart contract  630  or other chaincode) and data (e.g., distributed ledger, etc.). In this example, the API gateway  662  is a common interface for performing transactions (invoke, queries, etc.) on the blockchain by connecting one or more entities  652  and  656  to a blockchain peer (i.e., server  654 ). Here, the server  654  is a blockchain network peer component that holds a copy of the world state and a distributed ledger allowing clients  652  and  656  to query data on the world state as well as submit transactions into the blockchain network where, depending on the smart contract  630  and endorsement policy, endorsing peers will run the smart contracts  630 . 
     The above embodiments may be implemented in hardware, in a computer program executed by a processor, in firmware, or in a combination of the above. A computer program may be embodied on a computer readable medium, such as a storage medium. For example, a computer program may reside in random access memory (“RAM”), flash memory, read-only memory (“ROM”), erasable programmable read-only memory (“EPROM”), electrically erasable programmable read-only memory (“EEPROM”), registers, hard disk, a removable disk, a compact disk read-only memory (“CD-ROM”), or any other form of storage medium known in the art. 
     An exemplary storage medium may be coupled to the processor such that the processor may read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an application specific integrated circuit (“ASIC”). In the alternative, the processor and the storage medium may reside as discrete components. 
       FIG. 7A  illustrates a process  700  of a new block being added to a distributed ledger  720 , according to example embodiments, and  FIG. 7B  illustrates contents of a new data block structure  730  for blockchain, according to example embodiments. Referring to  FIG. 7A , clients (not shown) may submit transactions to blockchain nodes  711 ,  712 , and/or  713 . Clients may be instructions received from any source to enact activity on the blockchain  720 . As an example, clients may be applications that act on behalf of a requester, such as a device, person or entity to propose transactions for the blockchain. The plurality of blockchain peers (e.g., blockchain nodes  711 ,  712 , and  713 ) may maintain a state of the blockchain network and a copy of the distributed ledger  720 . Different types of blockchain nodes/peers may be present in the blockchain network including endorsing peers which simulate and endorse transactions proposed by clients and committing peers which verify endorsements, validate transactions, and commit transactions to the distributed ledger  720 . In this example, the blockchain nodes  711 ,  712 , and  713  may perform the role of endorser node, committer node, or both. 
     The distributed ledger  720  includes a blockchain which stores immutable, sequenced records in blocks, and a state database  724  (current world state) maintaining a current state of the blockchain  722 . One distributed ledger  720  may exist per channel and each peer maintains its own copy of the distributed ledger  720  for each channel of which they are a member. The blockchain  722  is a transaction log, structured as hash-linked blocks where each block contains a sequence of N transactions. Blocks may include various components such as shown in  FIG. 7B . The linking of the blocks (shown by arrows in  FIG. 7A ) may be generated by adding a hash of a prior block&#39;s header within a block header of a current block. In this way, all transactions on the blockchain  722  are sequenced and cryptographically linked together preventing tampering with blockchain data without breaking the hash links. Furthermore, because of the links, the latest block in the blockchain  722  represents every transaction that has come before it. The blockchain  722  may be stored on a peer file system (local or attached storage), which supports an append-only blockchain workload. 
     The current state of the blockchain  722  and the distributed ledger  722  may be stored in the state database  724 . Here, the current state data represents the latest values for all keys ever included in the chain transaction log of the blockchain  722 . Chaincode invocations execute transactions against the current state in the state database  724 . To make these chaincode interactions extremely efficient, the latest values of all keys are stored in the state database  724 . The state database  724  may include an indexed view into the transaction log of the blockchain  722 , it can therefore be regenerated from the chain at any time. The state database  724  may automatically get recovered (or generated if needed) upon peer startup, before transactions are accepted. 
     Endorsing nodes receive transactions from clients and endorse the transaction based on simulated results. Endorsing nodes hold smart contracts which simulate the transaction proposals. When an endorsing node endorses a transaction, the endorsing nodes creates a transaction endorsement which is a signed response from the endorsing node to the client application indicating the endorsement of the simulated transaction. The method of endorsing a transaction depends on an endorsement policy which may be specified within chaincode. An example of an endorsement policy is “the majority of endorsing peers must endorse the transaction”. Different channels may have different endorsement policies. Endorsed transactions are forward by the client application to ordering service  710 . 
     The ordering service  710  accepts endorsed transactions, orders them into a block, and delivers the blocks to the committing peers. For example, the ordering service  710  may initiate a new block when a threshold of transactions has been reached, a timer times out, or another condition. In the example of  FIG. 7A , blockchain node  712  is a committing peer that has received a new data new data block  730  for storage on blockchain  720 . The first block in the blockchain may be referred to as a genesis block which includes information about the blockchain, its members, the data stored therein, etc. 
     The ordering service  710  may be made up of a cluster of orderers. The ordering service  710  does not process transactions, smart contracts, or maintain the shared ledger. Rather, the ordering service  710  may accept the endorsed transactions and specifies the order in which those transactions are committed to the distributed ledger  720 . The architecture of the blockchain network may be designed such that the specific implementation of ‘ordering’ (e.g., Solo, Kafka, BFT, etc.) becomes a pluggable component. 
     Transactions are written to the distributed ledger  720  in a consistent order. The order of transactions is established to ensure that the updates to the state database  724  are valid when they are committed to the network. Unlike a cryptocurrency blockchain system (e.g., Bitcoin, etc.) where ordering occurs through the solving of a cryptographic puzzle, or mining, in this example the parties of the distributed ledger  720  may choose the ordering mechanism that best suits that network. 
     When the ordering service  710  initializes a new data block  730 , the new data block  730  may be broadcast to committing peers (e.g., blockchain nodes  711 ,  712 , and  713 ). In response, each committing peer validates the transaction within the new data block  730  by checking to make sure that the read set and the write set still match the current world state in the state database  724 . Specifically, the committing peer can determine whether the read data that existed when the endorsers simulated the transaction is identical to the current world state in the state database  724 . When the committing peer validates the transaction, the transaction is written to the blockchain  722  on the distributed ledger  720 , and the state database  724  is updated with the write data from the read-write set. If a transaction fails, that is, if the committing peer finds that the read-write set does not match the current world state in the state database  724 , the transaction ordered into a block will still be included in that block, but it will be marked as invalid, and the state database  724  will not be updated. 
     Referring to  FIG. 7B , a new data block  730  (also referred to as a data block) that is stored on the blockchain  722  of the distributed ledger  720  may include multiple data segments such as a block header  740 , block data  750  (block data section), and block metadata  760 . It should be appreciated that the various depicted blocks and their contents, such as new data block  730  and its contents, shown in  FIG. 7B  are merely examples and are not meant to limit the scope of the example embodiments. In a conventional block, the data section may store transactional information of N transaction(s) (e.g., 1, 10, 100, 500, 1000, 2000, 3000, etc.) within the block data  750 . 
     The new data block  730  may include a link to a previous block (e.g., on the blockchain  722  in  FIG. 7A ) within the block header  740 . In particular, the block header  740  may include a hash of a previous block&#39;s header. The block header  740  may also include a unique block number, a hash of the block data  750  of the new data block  730 , and the like. The block number of the new data block  730  may be unique and assigned in various orders, such as an incremental/sequential order starting from zero. 
     According to various embodiments, the block data  750  may store a pruned data structure  750  (or hash of a pruned data structure, etc.). For example, the pruned data structure  752  may include a format of a predefined schema with specific fields defined by the schema. The pruned data structure  752  may be arranged in a hierarchical tree structure and hashed to generate a root hash of the tree before being stored on the block data  750 . According to various embodiments, the pruned data structure  752  can be stored in an immutable log of blocks on the distributed ledger  720 . Some of the benefits of storing the pruned data structure  752  on the blockchain are reflected in the various embodiments disclosed and depicted herein. Although in  FIG. 7B , the pruned data structure  752  is depicted in the block data  750 , in other embodiments, the pruned data structure  752  may be located in the block header  740  or the block metadata  760 . 
     The block metadata  760  may store multiple fields of metadata (e.g., as a byte array, etc.). Metadata fields may include signature on block creation, a reference to a last configuration block, a transaction filter identifying valid and invalid transactions within the block, last offset persisted of an ordering service that ordered the block, and the like. The signature, the last configuration block, and the orderer metadata may be added by the ordering service  710 . Meanwhile, a committer of the block (such as blockchain node  712 ) may add validity/invalidity information based on an endorsement policy, verification of read/write sets, and the like. The transaction filter may include a byte array of a size equal to the number of transactions that are included in the block data  750  and a validation code identifying whether a transaction was valid/invalid. 
       FIG. 7C  illustrates an embodiment of a blockchain  770  for digital content in accordance with the embodiments described herein. The digital content may include one or more files and associated information. The files may include media, images, video, audio, text, links, graphics, animations, web pages, documents, or other forms of digital content. The immutable, append-only aspects of the blockchain serve as a safeguard to protect the integrity, validity, and authenticity of the digital content, making it suitable use in legal proceedings where admissibility rules apply or other settings where evidence is taken into consideration or where the presentation and use of digital information is otherwise of interest. In this case, the digital content may be referred to as digital evidence. 
     The blockchain may be formed in various ways. In one embodiment, the digital content may be included in and accessed from the blockchain itself. For example, each block of the blockchain may store a hash value of reference information (e.g., header, value, etc.) along the associated digital content. The hash value and associated digital content may then be encrypted together. Thus, the digital content of each block may be accessed by decrypting each block in the blockchain, and the hash value of each block may be used as a basis to reference a previous block. This may be illustrated as follows: 
     
       
         
           
               
               
               
               
             
               
                   
               
               
                 Block 1 
                 Block 2 
                 . . . 
                 Block N 
               
               
                   
               
             
            
               
                 Hash Value 1 
                 Hash Value 2 
                   
                 Hash Value N 
               
               
                 Digital Content 1 
                 Digital Content 2 
                   
                 Digital Content N 
               
               
                   
               
            
           
         
       
     
     In one embodiment, the digital content may be not included in the blockchain. For example, the blockchain may store the encrypted hashes of the content of each block without any of the digital content. The digital content may be stored in another storage area or memory address in association with the hash value of the original file. The other storage area may be the same storage device used to store the blockchain or may be a different storage area or even a separate relational database. The digital content of each block may be referenced or accessed by obtaining or querying the hash value of a block of interest and then looking up that has value in the storage area, which is stored in correspondence with the actual digital content. This operation may be performed, for example, a database gatekeeper. This may be illustrated as follows: 
     
       
         
           
               
               
               
             
               
                   
                   
               
               
                   
                 Blockchain 
                 Storage Area 
               
               
                   
                   
               
             
            
               
                   
                 Block 1 Hash Value 
                 Block 1 Hash Value . . . Content 
               
               
                   
                 . 
                 . 
               
               
                   
                 . 
                 . 
               
               
                   
                 . 
                 . 
               
               
                   
                 Block N Hash Value 
                 Block N Hash Value . . . Content 
               
               
                   
                   
               
            
           
         
       
     
     In the example embodiment of  FIG. 7C , the blockchain  770  includes a number of blocks  778   1 ,  778   2 , . . .  778   N  cryptographically linked in an ordered sequence, where N≥1. The encryption used to link the blocks  778   1 ,  778   2 , . . .  778   N  may be any of a number of keyed or un-keyed Hash functions. In one embodiment, the blocks  778   1 ,  778   2 , . . .  778   N  are subject to a hash function which produces n-bit alphanumeric outputs (where n is 256 or another number) from inputs that are based on information in the blocks. Examples of such a hash function include, but are not limited to, a SHA-type (SHA stands for Secured Hash Algorithm) algorithm, Merkle-Damgard algorithm, HAIFA algorithm, Merkle-tree algorithm, nonce-based algorithm, and a non-collision-resistant PRF algorithm. In another embodiment, the blocks  778   1 ,  778   2 , . . . ,  778   N  may be cryptographically linked by a function that is different from a hash function. For purposes of illustration, the following description is made with reference to a hash function, e.g., SHA-2. 
     Each of the blocks  778   1 ,  778   2 , . . . ,  778   N  in the blockchain includes a header, a version of the file, and a value. The header and the value are different for each block as a result of hashing in the blockchain. In one embodiment, the value may be included in the header. As described in greater detail below, the version of the file may be the original file or a different version of the original file. 
     The first block  778   1  in the blockchain is referred to as the genesis block and includes the header  772   1 , original file  774   1 , and an initial value  776   1 . The hashing scheme used for the genesis block, and indeed in all subsequent blocks, may vary. For example, all the information in the first block  778   1  may be hashed together and at one time, or each or a portion of the information in the first block  778   1  may be separately hashed and then a hash of the separately hashed portions may be performed. 
     The header  772   1  may include one or more initial parameters, which, for example, may include a version number, timestamp, nonce, root information, difficulty level, consensus protocol, duration, media format, source, descriptive keywords, and/or other information associated with original file  774   1  and/or the blockchain. The header  772   1  may be generated automatically (e.g., by blockchain network managing software) or manually by a blockchain participant. Unlike the header in other blocks  778   2  to  778   N  in the blockchain, the header  772   1  in the genesis block does not reference a previous block, simply because there is no previous block. 
     The original file  774   1  in the genesis block may be, for example, data as captured by a device with or without processing prior to its inclusion in the blockchain. The original file  774   1  is received through the interface of the system from the device, media source, or node. The original file  774   1  is associated with metadata, which, for example, may be generated by a user, the device, and/or the system processor, either manually or automatically. The metadata may be included in the first block  778   1  in association with the original file  774   1 . 
     The value  776   1  in the genesis block is an initial value generated based on one or more unique attributes of the original file  774   1 . In one embodiment, the one or more unique attributes may include the hash value for the original file  774   1 , metadata for the original file  774   1 , and other information associated with the file. In one implementation, the initial value  776   1  may be based on the following unique attributes:
         1) SHA-2 computed hash value for the original file   2) originating device ID   3) starting timestamp for the original file   4) initial storage location of the original file   5) blockchain network member ID for software to currently control the original file and associated metadata       

     The other blocks  778   2  to  778   N  in the blockchain also have headers, files, and values. However, unlike the first block  772   1 , each of the headers  772   2  to  772   N  in the other blocks includes the hash value of an immediately preceding block. The hash value of the immediately preceding block may be just the hash of the header of the previous block or may be the hash value of the entire previous block. By including the hash value of a preceding block in each of the remaining blocks, a trace can be performed from the Nth block back to the genesis block (and the associated original file) on a block-by-block basis, as indicated by arrows  780 , to establish an auditable and immutable chain-of-custody. 
     Each of the header  772   2  to  772   N  in the other blocks may also include other information, e.g., version number, timestamp, nonce, root information, difficulty level, consensus protocol, and/or other parameters or information associated with the corresponding files and/or the blockchain in general. 
     The files  774   2  to  774   N  in the other blocks may be equal to the original file or may be a modified version of the original file in the genesis block depending, for example, on the type of processing performed. The type of processing performed may vary from block to block. The processing may involve, for example, any modification of a file in a preceding block, such as redacting information or otherwise changing the content of, taking information away from, or adding or appending information to the files. 
     Additionally, or alternatively, the processing may involve merely copying the file from a preceding block, changing a storage location of the file, analyzing the file from one or more preceding blocks, moving the file from one storage or memory location to another, or performing action relative to the file of the blockchain and/or its associated metadata. Processing which involves analyzing a file may include, for example, appending, including, or otherwise associating various analytics, statistics, or other information associated with the file. 
     The values in each of the other blocks  776   2  to  776   N  in the other blocks are unique values and are all different as a result of the processing performed. For example, the value in any one block corresponds to an updated version of the value in the previous block. The update is reflected in the hash of the block to which the value is assigned. The values of the blocks therefore provide an indication of what processing was performed in the blocks and also permit a tracing through the blockchain back to the original file. This tracking confirms the chain-of-custody of the file throughout the entire blockchain. 
     For example, consider the case where portions of the file in a previous block are redacted, blocked out, or pixelated in order to protect the identity of a person shown in the file. In this case, the block including the redacted file will include metadata associated with the redacted file, e.g., how the redaction was performed, who performed the redaction, timestamps where the redaction(s) occurred, etc. The metadata may be hashed to form the value. Because the metadata for the block is different from the information that was hashed to form the value in the previous block, the values are different from one another and may be recovered when decrypted. 
     In one embodiment, the value of a previous block may be updated (e.g., a new hash value computed) to form the value of a current block when any one or more of the following occurs. The new hash value may be computed by hashing all or a portion of the information noted below, in this example embodiment.
         a) new SHA-2 computed hash value if the file has been processed in any way (e.g., if the file was redacted, copied, altered, accessed, or some other action was taken)   b) new storage location for the file   c) new metadata identified associated with the file   d) transfer of access or control of the file from one blockchain participant to another blockchain participant       

       FIG. 7D  illustrates an embodiment of a block which may represent the structure of the blocks in the blockchain  790  in accordance with one embodiment. The block, Block i , includes a header  772   i , a file  774   i , and a value  776   i . 
     The header  772   i  includes a hash value of a previous block Block i−1  and additional reference information, which, for example, may be any of the types of information (e.g., header information including references, characteristics, parameters, etc.) discussed herein. All blocks reference the hash of a previous block except, of course, the genesis block. The hash value of the previous block may be just a hash of the header in the previous block or a hash of all or a portion of the information in the previous block, including the file and metadata. 
     The file  774   i  includes a plurality of data, such as Data  1 , Data  2 , . . . , Data N in sequence. The data are tagged with Metadata  1 , Metadata  2 , . . . , Metadata N which describe the content and/or characteristics associated with the data. For example, the metadata for each data may include information to indicate a timestamp for the data, process the data, keywords indicating the persons or other content depicted in the data, and/or other features that may be helpful to establish the validity and content of the file as a whole, and particularly its use a digital evidence, for example, as described in connection with an embodiment discussed below. In addition to the metadata, each data may be tagged with reference REF 1 , REF 2 , . . . , REF N  to a previous data to prevent tampering, gaps in the file, and sequential reference through the file. 
     Once the metadata is assigned to the data (e.g., through a smart contract), the metadata cannot be altered without the hash changing, which can easily be identified for invalidation. The metadata, thus, creates a data log of information that may be accessed for use by participants in the blockchain. 
     The value  776   i  is a hash value or other value computed based on any of the types of information previously discussed. For example, for any given block Block i , the value for that block may be updated to reflect the processing that was performed for that block, e.g., new hash value, new storage location, new metadata for the associated file, transfer of control or access, identifier, or other action or information to be added. Although the value in each block is shown to be separate from the metadata for the data of the file and header, the value may be based, in part or whole, on this metadata in another embodiment. 
     Once the blockchain  770  is formed, at any point in time, the immutable chain-of-custody for the file may be obtained by querying the blockchain for the transaction history of the values across the blocks. This query, or tracking procedure, may begin with decrypting the value of the block that is most currently included (e.g., the last (N th ) block), and then continuing to decrypt the value of the other blocks until the genesis block is reached and the original file is recovered. The decryption may involve decrypting the headers and files and associated metadata at each block, as well. 
     Decryption is performed based on the type of encryption that took place in each block. This may involve the use of private keys, public keys, or a public key-private key pair. For example, when asymmetric encryption is used, blockchain participants or a processor in the network may generate a public key and private key pair using a predetermined algorithm. The public key and private key are associated with each other through some mathematical relationship. The public key may be distributed publicly to serve as an address to receive messages from other users, e.g., an IP address or home address. The private key is kept secret and used to digitally sign messages sent to other blockchain participants. The signature is included in the message so that the recipient can verify using the public key of the sender. This way, the recipient can be sure that only the sender could have sent this message. 
     Generating a key pair may be analogous to creating an account on the blockchain, but without having to actually register anywhere. Also, every transaction that is executed on the blockchain is digitally signed by the sender using their private key. This signature ensures that only the owner of the account can track and process (if within the scope of permission determined by a smart contract) the file of the blockchain. 
       FIGS. 8A and 8B  illustrate additional examples of use cases for blockchain which may be incorporated and used herein. In particular,  FIG. 8A  illustrates an example  800  of a blockchain  810  which stores machine learning (artificial intelligence) data. Machine learning relies on vast quantities of historical data (or training data) to build predictive models for accurate prediction on new data. Machine learning software (e.g., neural networks, etc.) can often sift through millions of records to unearth non-intuitive patterns. 
     In the example of  FIG. 8A , a host platform  820  builds and deploys a machine learning model for predictive monitoring of assets  830 . Here, the host platform  820  may be a cloud platform, an industrial server, a web server, a personal computer, a user device, and the like. Assets  830  can be any type of asset (e.g., machine or equipment, etc.) such as an aircraft, locomotive, turbine, medical machinery and equipment, oil and gas equipment, boats, ships, vehicles, and the like. As another example, assets  830  may be non-tangible assets such as stocks, currency, digital coins, insurance, or the like. 
     The blockchain  810  can be used to significantly improve both a training process  802  of the machine learning model and a predictive process  804  based on a trained machine learning model. For example, in  802 , rather than requiring a data scientist/engineer or other user to collect the data, historical data may be stored by the assets  830  themselves (or through an intermediary, not shown) on the blockchain  810 . This can significantly reduce the collection time needed by the host platform  820  when performing predictive model training. For example, using smart contracts, data can be directly and reliably transferred straight from its place of origin to the blockchain  810 . By using the blockchain  810  to ensure the security and ownership of the collected data, smart contracts may directly send the data from the assets to the individuals that use the data for building a machine learning model. This allows for sharing of data among the assets  830 . 
     The collected data may be stored in the blockchain  810  based on a consensus mechanism. The consensus mechanism pulls in (permissioned nodes) to ensure that the data being recorded is verified and accurate. The data recorded is time-stamped, cryptographically signed, and immutable. It is therefore auditable, transparent, and secure. Adding IoT devices which write directly to the blockchain can, in certain cases (i.e. supply chain, healthcare, logistics, etc.), increase both the frequency and accuracy of the data being recorded. 
     Furthermore, training of the machine learning model on the collected data may take rounds of refinement and testing by the host platform  820 . Each round may be based on additional data or data that was not previously considered to help expand the knowledge of the machine learning model. In  802 , the different training and testing steps (and the data associated therewith) may be stored on the blockchain  810  by the host platform  820 . Each refinement of the machine learning model (e.g., changes in variables, weights, etc.) may be stored on the blockchain  810 . This provides verifiable proof of how the model was trained and what data was used to train the model. Furthermore, when the host platform  820  has achieved a finally trained model, the resulting model may be stored on the blockchain  810 . 
     After the model has been trained, it may be deployed to a live environment where it can make predictions/decisions based on the execution of the final trained machine learning model. For example, in  804 , the machine learning model may be used for condition-based maintenance (CBM) for an asset such as an aircraft, a wind turbine, a healthcare machine, and the like. In this example, data fed back from the asset  830  may be input the machine learning model and used to make event predictions such as failure events, error codes, and the like. Determinations made by the execution of the machine learning model at the host platform  820  may be stored on the blockchain  810  to provide auditable/verifiable proof. As one non-limiting example, the machine learning model may predict a future breakdown/failure to a part of the asset  830  and create alert or a notification to replace the part. The data behind this decision may be stored by the host platform  820  on the blockchain  810 . In one embodiment the features and/or the actions described and/or depicted herein can occur on or with respect to the blockchain  810 . 
     New transactions for a blockchain can be gathered together into a new block and added to an existing hash value. This is then encrypted to create a new hash for the new block. This is added to the next list of transactions when they are encrypted, and so on. The result is a chain of blocks that each contain the hash values of all preceding blocks. Computers that store these blocks regularly compare their hash values to ensure that they are all in agreement. Any computer that does not agree, discards the records that are causing the problem. This approach is good for ensuring tamper-resistance of the blockchain, but it is not perfect. 
     One way to game this system is for a dishonest user to change the list of transactions in their favor, but in a way that leaves the hash unchanged. This can be done by brute force, in other words by changing a record, encrypting the result, and seeing whether the hash value is the same. And if not, trying again and again and again until it finds a hash that matches. The security of blockchains is based on the belief that ordinary computers can only perform this kind of brute force attack over time scales that are entirely impractical, such as the age of the universe. By contrast, quantum computers are much faster (1000s of times faster) and consequently pose a much greater threat. 
       FIG. 8B  illustrates an example  850  of a quantum-secure blockchain  852  which implements quantum key distribution (QKD) to protect against a quantum computing attack. In this example, blockchain users can verify each other&#39;s identities using QKD. This sends information using quantum particles such as photons, which cannot be copied by an eavesdropper without destroying them. In this way, a sender and a receiver through the blockchain can be sure of each other&#39;s identity. 
     In the example of  FIG. 8B , four users are present  854 ,  856 ,  858 , and  860 . Each of pair of users may share a secret key  862  (i.e., a QKD) between themselves. Since there are four nodes in this example, six pairs of nodes exists, and therefore six different secret keys  862  are used including QKD AB , QKD AC , QKD AD , QKD BC , QKD BD , and QKD CD . Each pair can create a QKD by sending information using quantum particles such as photons, which cannot be copied by an eavesdropper without destroying them. In this way, a pair of users can be sure of each other&#39;s identity. 
     The operation of the blockchain  852  is based on two procedures (i) creation of transactions, and (ii) construction of blocks that aggregate the new transactions. New transactions may be created similar to a traditional blockchain network. Each transaction may contain information about a sender, a receiver, a time of creation, an amount (or value) to be transferred, a list of reference transactions that justifies the sender has funds for the operation, and the like. This transaction record is then sent to all other nodes where it is entered into a pool of unconfirmed transactions. Here, two parties (i.e., a pair of users from among  854 - 860 ) authenticate the transaction by providing their shared secret key  862  (QKD). This quantum signature can be attached to every transaction making it exceedingly difficult to tamper with. Each node checks their entries with respect to a local copy of the blockchain  852  to verify that each transaction has sufficient funds. However, the transactions are not yet confirmed. 
     Rather than perform a traditional mining process on the blocks, the blocks may be created in a decentralized manner using a broadcast protocol. At a predetermined period of time (e.g., seconds, minutes, hours, etc.) the network may apply the broadcast protocol to any unconfirmed transaction thereby to achieve a Byzantine agreement (consensus) regarding a correct version of the transaction. For example, each node may possess a private value (transaction data of that particular node). In a first round, nodes transmit their private values to each other. In subsequent rounds, nodes communicate the information they received in the previous round from other nodes. Here, honest nodes are able to create a complete set of transactions within a new block. This new block can be added to the blockchain  852 . In one embodiment the features and/or the actions described and/or depicted herein can occur on or with respect to the blockchain  852 . 
       FIG. 9  illustrates an example system  900  that supports one or more of the example embodiments described and/or depicted herein. The system  900  comprises a computer system/server  902 , which is operational with numerous other general purpose or special purpose computing system environments or configurations. Examples of well-known computing systems, environments, and/or configurations that may be suitable for use with computer system/server  902  include, but are not limited to, personal computer systems, server computer systems, thin clients, thick clients, hand-held or laptop devices, multiprocessor systems, microprocessor-based systems, set top boxes, programmable consumer electronics, network PCs, minicomputer systems, mainframe computer systems, and distributed cloud computing environments that include any of the above systems or devices, and the like. 
     Computer system/server  902  may be described in the general context of computer system-executable instructions, such as program modules, being executed by a computer system. Generally, program modules may include routines, programs, objects, components, logic, data structures, and so on that perform particular tasks or implement particular abstract data types. Computer system/server  902  may be practiced in distributed cloud computing environments where tasks are performed by remote processing devices that are linked through a communications network. In a distributed cloud computing environment, program modules may be located in both local and remote computer system storage media including memory storage devices. 
     As shown in  FIG. 9 , computer system/server  902  in cloud computing node  900  is shown in the form of a general-purpose computing device. The components of computer system/server  902  may include, but are not limited to, one or more processors or processing units  904 , a system memory  906 , and a bus that couples various system components including system memory  906  to processor  904 . 
     The bus represents one or more of any of several types of bus structures, including a memory bus or memory controller, a peripheral bus, an accelerated graphics port, and a processor or local bus using any of a variety of bus architectures. By way of example, and not limitation, such architectures include Industry Standard Architecture (ISA) bus, Micro Channel Architecture (MCA) bus, Enhanced ISA (EISA) bus, Video Electronics Standards Association (VESA) local bus, and Peripheral Component Interconnects (PCI) bus. 
     Computer system/server  902  typically includes a variety of computer system readable media. Such media may be any available media that is accessible by computer system/server  902 , and it includes both volatile and non-volatile media, removable and non-removable media. System memory  906 , in one embodiment, implements the flow diagrams of the other figures. The system memory  906  can include computer system readable media in the form of volatile memory, such as random-access memory (RAM)  910  and/or cache memory  912 . Computer system/server  902  may further include other removable/non-removable, volatile/non-volatile computer system storage media. By way of example only, storage system  914  can be provided for reading from and writing to a non-removable, non-volatile magnetic media (not shown and typically called a “hard drive”). Although not shown, a magnetic disk drive for reading from and writing to a removable, non-volatile magnetic disk (e.g., a “floppy disk”), and an optical disk drive for reading from or writing to a removable, non-volatile optical disk such as a CD-ROM, DVD-ROM or other optical media can be provided. In such instances, each can be connected to the bus by one or more data media interfaces. As will be further depicted and described below, memory  906  may include at least one program product having a set (e.g., at least one) of program modules that are configured to carry out the functions of various embodiments of the application. 
     Program/utility  916 , having a set (at least one) of program modules  918 , may be stored in memory  906  by way of example, and not limitation, as well as an operating system, one or more application programs, other program modules, and program data. Each of the operating system, one or more application programs, other program modules, and program data or some combination thereof, may include an implementation of a networking environment. Program modules  918  generally carry out the functions and/or methodologies of various embodiments of the application as described herein. 
     As will be appreciated by one skilled in the art, aspects of the present application may be embodied as a system, method, or computer program product. Accordingly, aspects of the present application may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system.” Furthermore, aspects of the present application may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied thereon. 
     Computer system/server  902  may also communicate with one or more external devices  920  such as a keyboard, a pointing device, a display  922 , etc.; one or more devices that enable a user to interact with computer system/server  902 ; and/or any devices (e.g., network card, modem, etc.) that enable computer system/server  902  to communicate with one or more other computing devices. Such communication can occur via I/O interfaces  924 . Still yet, computer system/server  902  can communicate with one or more networks such as a local area network (LAN), a general wide area network (WAN), and/or a public network (e.g., the Internet) via network adapter  926 . As depicted, network adapter  926  communicates with the other components of computer system/server  902  via a bus. It should be understood that although not shown, other hardware and/or software components could be used in conjunction with computer system/server  902 . Examples include, but are not limited to: microcode, device drivers, redundant processing units, external disk drive arrays, RAID systems, tape drives, and data archival storage systems, etc. 
     Although an exemplary embodiment of at least one of a system, method, and non-transitory computer readable medium has been illustrated in the accompanied drawings and described in the foregoing detailed description, it will be understood that the application is not limited to the embodiments disclosed, but is capable of numerous rearrangements, modifications, and substitutions as set forth and defined by the following claims. For example, the capabilities of the system of the various figures can be performed by one or more of the modules or components described herein or in a distributed architecture and may include a transmitter, receiver or pair of both. For example, all or part of the functionality performed by the individual modules, may be performed by one or more of these modules. Further, the functionality described herein may be performed at various times and in relation to various events, internal or external to the modules or components. Also, the information sent between various modules can be sent between the modules via at least one of: a data network, the Internet, a voice network, an Internet Protocol network, a wireless device, a wired device and/or via plurality of protocols. Also, the messages sent or received by any of the modules may be sent or received directly and/or via one or more of the other modules. 
     One skilled in the art will appreciate that a “system” could be embodied as a personal computer, a server, a console, a personal digital assistant (PDA), a cell phone, a tablet computing device, a smartphone or any other suitable computing device, or combination of devices. Presenting the above-described functions as being performed by a “system” is not intended to limit the scope of the present application in any way but is intended to provide one example of many embodiments. Indeed, methods, systems and apparatuses disclosed herein may be implemented in localized and distributed forms consistent with computing technology. 
     It should be noted that some of the system features described in this specification have been presented as modules, in order to more particularly emphasize their implementation independence. For example, a module may be implemented as a hardware circuit comprising custom very large-scale integration (VLSI) circuits or gate arrays, off-the-shelf semiconductors such as logic chips, transistors, or other discrete components. A module may also be implemented in programmable hardware devices such as field programmable gate arrays, programmable array logic, programmable logic devices, graphics processing units, or the like. 
     A module may also be at least partially implemented in software for execution by various types of processors. An identified unit of executable code may, for instance, comprise one or more physical or logical blocks of computer instructions that may, for instance, be organized as an object, procedure, or function. Nevertheless, the executables of an identified module need not be physically located together but may comprise disparate instructions stored in different locations which, when joined logically together, comprise the module and achieve the stated purpose for the module. Further, modules may be stored on a computer-readable medium, which may be, for instance, a hard disk drive, flash device, random access memory (RAM), tape, or any other such medium used to store data. 
     Indeed, a module of executable code could be a single instruction, or many instructions, and may even be distributed over several different code segments, among different programs, and across several memory devices. Similarly, operational data may be identified and illustrated herein within modules and may be embodied in any suitable form and organized within any suitable type of data structure. The operational data may be collected as a single data set or may be distributed over different locations including over different storage devices, and may exist, at least partially, merely as electronic signals on a system or network. 
     It will be readily understood that the components of the application, as generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations. Thus, the detailed description of the embodiments is not intended to limit the scope of the application as claimed but is merely representative of selected embodiments of the application. 
     One having ordinary skill in the art will readily understand that the above may be practiced with steps in a different order, and/or with hardware elements in configurations that are different than those which are disclosed. Therefore, although the application has been described based upon these preferred embodiments, it would be apparent to those of skill in the art that certain modifications, variations, and alternative constructions would be apparent. 
     While preferred embodiments of the present application have been described, it is to be understood that the embodiments described are illustrative only and the scope of the application is to be defined solely by the appended claims when considered with a full range of equivalents and modifications (e.g., protocols, hardware devices, software platforms etc.) thereto.