Patent Publication Number: US-11641364-B2

Title: Cross-domain state synchronization

Description:
TECHNICAL FIELD 
     This application generally relates to storing data via a blockchain, and more particularly, to a controlled interface for synchronizing ledger state between different security domains in a multi-domain blockchain network. 
     BACKGROUND 
     A centralized database stores and maintains data in a single database (e.g., a database server) at one location. This location is often a central computer, for example, a desktop central processing unit (CPU), a server CPU, or a mainframe computer. Information stored on a centralized database is typically accessible from multiple different points. Multiple users or client workstations can work simultaneously on the centralized database, for example, based on a client/server configuration. A centralized database is easy to manage, maintain, and control, especially for purposes of security because of its single location. Within a centralized database, 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. 
     Meanwhile, blockchain systems store data on an immutable ledger, provide distributed and decentralized access to the immutable ledger through non-trusting participants, establish consensus requirements for agreement between the non-trusting participants such that no one entity can change the immutable ledger without agreement from others, invoke smart contracts, and the like. A blockchain is formed by a network of participants which agree to add a block (with data stored therein) to the immutable ledger. Before being added, the block is linked to a previous block on the immutable ledger thereby forming a chain. This immutable and incorruptible nature of blockchain makes it safe from falsified information and hacks. The decentralized nature also gives it the unique quality of being trustless, in that parties do not need to establish trust before they can transact safely. 
     SUMMARY 
     One example embodiment provides an apparatus that includes one or more of a network interface configured to receive a gossip message originated from a domain anchor peer in a first security domain, and a processor configured to one or more of verify that block content within the gossip message does not violate a cross-domain security policy, and in response to verification of the block content, update an endpoint of the gossip message with an address of a domain anchor peer in a second security domain, wherein the processor may be further configured to control the network interface to transmit the updated gossip message to the domain anchor peer in the second security domain. 
     Another example embodiment provides a method that includes one or more of receiving a gossip message originated from a domain anchor peer in a first security domain, verifying that block content within the gossip message does not violate a cross-domain security policy, in response to verifying the block content, updating an endpoint of the gossip message with an address of a domain anchor peer in a second security domain, and transmitting the updated gossip message to the domain anchor peer in the second security domain. 
     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 a gossip message originated from a domain anchor peer in a first security domain, verifying that block content within the gossip message does not violate a cross-domain security policy, in response to verifying the block content, updating an endpoint of the gossip message with an address of a domain anchor peer in a second security domain, and transmitting the updated gossip message to the domain anchor peer in the second security domain. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1 A  is a diagram illustrating a multi-domain blockchain network for cross-domain control according to example embodiments. 
         FIG.  1 B  is a diagram illustrating a multi-domain blockchain network for synchronizing ledger state according to example embodiments. 
         FIG.  2 A  is a diagram illustrating an example blockchain architecture configuration, according to example embodiments. 
         FIG.  2 B  is a diagram illustrating a blockchain transactional flow among nodes, according to example embodiments. 
         FIG.  3 A  is a diagram illustrating a permissioned network, according to example embodiments. 
         FIG.  3 B  is a diagram illustrating another permissioned network, according to example embodiments. 
         FIG.  3 C  is a diagram illustrating a permissionless network, according to example embodiments. 
         FIG.  4 A  is a diagram illustrating a process of gossip exchange between a domain anchor peer and a multi-domain relay according to example embodiments. 
         FIG.  4 B  is a diagram illustrating a process of exchanging gossip content between different domains in a blockchain network according to example embodiments. 
         FIG.  5    is a diagram illustrating a method of synchronizing state among different security domains according to example embodiments. 
         FIG.  6 A  is a diagram illustrating an example system configured to perform one or more operations described herein, according to example embodiments. 
         FIG.  6 B  is a diagram illustrating another example system configured to perform one or more operations described herein, according to example embodiments. 
         FIG.  6 C  is a diagram illustrating a further example system configured to utilize a smart contract, according to example embodiments. 
         FIG.  6 D  is a diagram illustrating yet another example system configured to utilize a blockchain, according to example embodiments. 
         FIG.  7 A  is a diagram illustrating a process of a new block being added to a distributed ledger, according to example embodiments. 
         FIG.  7 B  is a diagram illustrating data contents of a new data block, according to example embodiments. 
         FIG.  7 C  is a diagram illustrating a blockchain for digital content, according to example embodiments. 
         FIG.  7 D  is a diagram illustrating a block which may represent the structure of blocks in the blockchain, according to example embodiments. 
         FIG.  8 A  is a diagram illustrating an example blockchain which stores machine learning (artificial intelligence) data, according to example embodiments. 
         FIG.  8 B  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 synchronize state between different security domains in a blockchain network through controlled gossip communication. 
     In one embodiment the 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. 
     A security domain, also referred to herein as a domain, may be a domain within which behaviors, interactions, and outcomes occur and that s defined by a governing security policy. For example, a security domain may be defined by rules for users, processes, systems, and services that apply to activity within the domain and activity with similar entities in the domain. A network with a different security domain may be kept separate from other networks. For example, a network interacting with restricted data may be kept separate from a network interacting with public data. Private networks may contain classified information that is only for authorized users or otherwise store information that it does not desire to share with users of other networks. 
     The example embodiments are directed to a single permissioned blockchain network in which different security domains exists. In these examples, each security domain/enclave includes its own dedicated blockchain peers that are not accessible outside of their respective domain. In other words, a peer in a first domain may not communicate with or be aware of a peer in a second domain. This helps maintain the isolation between the two domains. However, the different domains may share a blockchain ledger. In this example, block content stored on a blockchain ledger in each of the first and second domains may be the same content Such a network design enables more secure networks to interact with less secure networks on a limited basis. 
     As an example, the security domains may include a high-side security domain with stricter security controls and a low-side security domain with less strict security controls. However, it should be appreciated that any two or more differing computer domains with different policies may be implemented by the example embodiments. Therefore, it does not need to be a high-side and a low-side domain, but any type of blockchain networks which are private and which seek to share data with one another on a limited basis. 
     An intermediate interface may exist between the different security domains. The intermediate interface may also include controllers which detect when data is to be shared, and transfers the data to a block creator within the intermediate interface The block creator may receive the storage event and aggregate/accumulate storage events from the different domains until a block is full, a predetermined time has passed, or some other condition, and create a new data block where the events are stored as blockchain transactions. When ready, the data block is then transmitted from the block creator to the controllers in each respective domain, for storage on a blockchain ledger. In this way, although the peer nodes are unaware of the existence of the other nodes (and domains) they share the same data because the created blocks are stored among peer nodes on every domain. 
     However, the problem with this architecture is that once a block is stored in a domain, there is no way for the different security domains to ensure that the data remains consistent. While the block content may initially start out as the same in each security domain, there is no end-to-end provenance, controls, or assurance, to ensure that the state of the ledgers in the different security domains remains consistent. As a result, the states in the different security domains may become inconsistent with one another due to various issues such as malicious activity, transmission failure, and the like. If the blockchain ledgers in two different security domains in the same blockchain network become out of synch, new ledger updates may not be made because the committing peer validations may fail. Specifically, the read set generated by an endorsing node will not match a current state in a committing peer.) 
     The example embodiments overcome these drawbacks by extending the intermediate interface (or adding a new intermediate interface) for cross-domain synchronization between peer nodes in different security domains of a blockchain network. Here, the two security domains may operate/communicate via a multi-domain relay. The extended interface may enable gossip communication in a secure and limited manner between the two or more security domains. A multi-domain relay may communicate with a trusted domain-specific anchor peer in each domain and perform gossip communication therebetween. The multi-domain relay may also relay gossip messages (including state information of the blockchain ledger) from one security domain to another security domain without revealing any sensitive cross-membership information (e.g., channel information, peer IDs, peer addresses, etc.) between the two domains. For example, the multi-domain relay may communicate ledger state from a high side domain to a low side domain without revealing identifications of any peers that are members of the high side domain to the anchor peer in the low side domain. Thus, state information can be revealed without revealing sensitive membership information. 
     The example embodiments modify the gossip protocol of a blockchain network by removing channel membership information and peer identification information and enabling a multi-domain relay to insert endpoint information into a gossip message. In the example above, the multi-domain relay may receive a gossip message from the high side domain anchor peer with state information of the blockchain ledger in the high side. Here, the multi-domain relay may insert an endpoint of a low side domain anchor peer into the gossip message while removing or ensuring that any membership information of the high side domain is out of the gossip message. The multi-domain may then route the modified gossip message to the low side domain anchor peer. The process may be repeated in reverse as well. Thus, both sides (high and low) may share ledger state information via the multi-domain relay without revealing channel membership information. 
     Some of the benefits of the example embodiments include in-band end-to-end assurance of the integrity and consistency of shared data on a blockchain ledger. Accordingly, the high and low side peer ledgers and world state may remain consistent with each other across different security domain boundaries. The example embodiments can be used in any blockchain network where different security domains exist, for example, security domains with multiple access levels, multi jurisdictional domains, supply chains, information management, and the like. 
     This system ensures that only data conforming to the security and business policies of each security domain passes across a domain boundary via the gossip messages. In general, cross-domain policies prevent inappropriately classified information from passing from the higher-to-lower security network domains (referred to as spillage) and to prevent malicious data from flowing low-to-high (e.g., viruses, etc.) For example, information that is considered classified includes high-side host names, IP addresses, as well as classified content in the information itself. Information exchanges across boundaries between networks of differing security classifications require highly robust security controls to prevent spillage. The example embodiments can securely propagate gossip messages with only the shareable data among the different security domains while preventing unauthorized data from leaving the domain. 
       FIG.  1 A  illustrates a multi-domain blockchain network  100 A for cross-domain control according to example embodiments. Referring to  FIG.  1 A , the network  100 A includes two security domains, including a high-side domain  110  and a low-side domain  130 . Each of the domains  110  and  130  may include a network of computing systems (e.g., servers, user devices, databases, cloud platforms, etc.) such as a wide area network (WAN) or the like, which are not shown in the example of  FIG.  1 A  for brevity. In this example, the high-side domain  110  refers to a network having a higher security classification (e.g., stricter security policies) than a network included in the low-side domain  130 . Therefore, data cannot be freely transferred from the high-side domain  110  to the low-side domain  130 , and maybe vice versa. 
     In  FIG.  1 A , the network  100 A includes a control system which includes a block creator  120  system and a plurality of domain controllers  121  and  122 . In this example, the domain controller  121  corresponds to and may be implemented within the high-side domain  110  while the domain controller  122  corresponds to and may be implemented within the low-side domain  130 . In addition, the high-side domain  110  includes a subset of blockchain peer nodes  112  while the low-side domain  130  includes its own subset of blockchain peer nodes  132  which are logically and physically isolated from the blockchain peer nodes  112  from the high-side domain  110 . However, the high-side peer nodes  112  and the low-side peer nodes  132  can share a blockchain ledger  140  (i.e., distributed ledger) which may store a hash-linked chain of blocks (blockchain) including data such as network events, network information, security issues, and the like, which may be shared among the two domains  110  and  130 . 
     The block creator  120  provides a controlled interface for the secure propagation of transaction blocks between the different security domains to the shared blockchain ledger  140 . The block creator  120  may host and encapsulate the multi-domain block-creating mechanisms (e.g., orderers in Hyperledger Fabric, etc.) Furthermore, the block creator  120  may apply and enforce operating system (OS)-level security controls to protect hosted component processes and isolate the inter-connected domains from each other such as using mandatory access controls. 
     Smart contracts executed by peer nodes within each of the respective domains  110  and  130  may perform policy validation to ensure that the transaction satisfies the union of the security policies including both the high-side domain  110  and the low-side domain  130 . Here, the transaction has to satisfy the union of both security policies (i.e. what is common to both). In other words, a smart contract will not let a secret through because even though it is allowed on a high side by a first security policy it isn&#39;t allowed on low side because of a second security policy, or vice versa. Endorsed transactions satisfying the cross-domain security policy are then forwarded to the respective domain controller  121  or  122 , based on which domain the transaction arises in. 
     When one of the domain controllers  121  or  122  receives a storage event (e.g., a blockchain transaction), the respective domain controller  121  or  122  may perform a committing-peer validation to prevent unendorsed transactions from being promulgated to the block creator  120 . However, the domain controllers  121  and  122  may not re-execute the smart contracts. Instead, they may prevent unendorsed transactions from spilling out into the cross-domain blocks. In response to security policies of both domains being satisfied, the respective domain controller  121  or  122  may transfer the transaction to the block creator  120  where it can be added to a new data block and propagated among both domains. 
     The block creator  120  and domain controllers  121  and  122  together prevent any direct domain-to-domain communication and enforce cross-domain endorsement and content policies (i.e., ensuring that the storage event has been properly endorsed and contains no unauthorized information such as the original proposed transaction). The block creator  120  may ensure that prior to inclusion in a block, every transaction is inspected and validated. The block creator  120  may include domain security policies defined and approved by the operator(s) of the guard. The block creator  120  may only connect to the domain controllers  121  and  122 , thereby preventing connections with peer nodes and other computing systems in the respective domains  110  and  130 . The block creator  120  may not accept any form of communication from any other process than the domain controllers  121  and  122 . 
     Each of the domain controller processes  121  and  122  operate at the same security classification level as their respective domains and prevent unendorsed, improperly endorsed, or other type of invalid client-submitted transactions from ever reaching the block-creating mechanism  120  because the domain controllers  121  and  122  are the only external connection point for clients submitting transactions to the ledger from each domain. From a security standpoint, each domain controller  121  and  122  may be considered trusted because they are isolated and protected using high assurance security controls like the block creator. 
     For example, the block creator  120  and the domain controllers  121  and  122  may be isolated by network, storage, operating system with secure labels, virtual machine, container, secure service container (SSC), logical partition (LPAR), and the like. The domain controllers  121  and  122  may each be a high availability component. The domain controllers  121  and  122  receive, validate, and forward transactions from (untrusted) clients to the trusted block creator  120 , performing the same validation as a committing peer and applying any domain specific filtering policies. In some embodiments, the policies may be defined and approved by the providers/operators of the guard. Cross-domain compliant smart contracts executed by peer nodes during the endorsement phase generate the cross-domain compliant read/write sets. The function of the domain controllers is not to duplicate the endorsement process by re-running these smart contracts. Instead, their purpose is to prevent unendorsed, improperly endorsed, or other types of invalid client-submitted transactions from ever reaching the block-creating mechanism  120 . 
     When creating a new block, the block creator  120  may combine transactions (network events, etc.) occurring in separate domains (e.g., high-side domain  110  and low-side domain  130 , etc.) and create blocks with the combined transactions. The newly created blocks are independently sent to the domain controllers  121  and  122  of the high-side domain  110  and the low-side domain  130 , respectively. Each domain controller  121  and  122  distributes the blocks within its domain according to the domain distribution model/method. For example, the blocks may be replicated among the ledger which is distributed among the peer nodes  112  and  132 . 
     In  FIG.  1 A , the high-side domain  110  and the low-side domain  130  may be logically and physically separated by means of a controlled interface group (i.e., the block creator  120  and the respective domain controllers  121  and  122 ). The controlled interface applies the security controls that enforce the sharing policies of both networks despite the differing security policies. The controlled interface group may be constructed and independently certified so that it provides high assurance that the security controls cannot be intentionally or unintentionally bypassed. In this example, a single logical blockchain business network can span two physically separated network security domains where some nodes are located on high side and some on low side WANS. But all nodes in the business network have the same ledger data by way of the block creator and the domain controllers. 
     A traditional blockchain architecture cannot maintain privacy/security across two different security domains because it requires a direct network connection from a submitting peer to the block-creating mechanism (ordering node) and the block-creating mechanism doesn&#39;t prevent spillage of unauthorized data from one domain to another via unendorsed or improperly endorsed transactions. In the cross-domain solution, there can never be a direct network connection that spans the two separated network domains without violating a security policy. 
       FIG.  1 B  illustrates a multi-domain blockchain network  100 B for synchronizing ledger state according to example embodiments. Here, the multi-domain blockchain network  100 B may be an extension of the multi-domain blockchain network  100 A shown in  FIG.  1 A . In this example, a gossip interface exists between the high side domain  110  and the low side domain  130 . The interface includes a multi-domain relay  150  that is isolated from the high side domain  110  and the low side domain  130 . In this example, the blockchain peers  112  in the high side domain  110  are logically and physically isolated from the blockchain peers  132  in the low side domain  130 . The isolation may exist due to different domain security controls, etc. 
     In the example of  FIG.  1 B , only specialized domain anchor peers  151  and  152  inter-communicate with the multi-domain relay  150 . In this example, the domain anchor peer  151  is a high-side domain anchor node that manages its own copy of the high side blockchain ledger. Likewise, the domain anchor peer  152  is a low side anchor node that manages its own copy of the low side blockchain ledger. Each domain anchor peer  151  and  152  maintains its own respective ledger and world state database in a similar way as the high side peers  112  and the low side peers  132 , respectively. In addition, the high side domain anchor peer  151  may perform gossip protocol with the high side peers  112  to ensure that the high side blockchain ledger is consistent among the high side peers (including the high side domain anchor peer  151 ). Likewise, the low side domain anchor peer  152  may perform gossip protocol with the low side blockchain peers  132  to ensure that the low side blockchain ledger is consistent among the low side blockchain peers (including the low side domain anchor peer  152 ). 
     The gossip protocol may include a transmission of messages between peers in the same security domain. For example, same side peers may periodically broadcast alive messages to each other to let the other peers in the security domain know they are available. Furthermore, same sided peers may periodically transmit (e.g., to random peers or predetermined peers) block content stored therein to ensure that the peers maintain a consistent ledger state. The block content may include block hashes, transaction hashes, block numbers, timestamps, and the like, of blocks that are stored on a blockchain. Peers may also pull gossip from other peers in the same security domain. For example, if a peer disconnects from the network, it may retrieve any missed data via a pull mechanism. 
     The gossip protocol may be used to discover new peers in the network, ensure that previously identified peers are still alive, disseminate blockchain ledger data among the peers in the same security domain, bring newly connected peers up to speed on the ledger state, and the like. The messages may include channel information identifying which peers are part of the same channel (security domain). 
     However, the high side peers  112  (including the high side anchor peer  151 ) cannot communicate with the low side peers  132  (including the low side anchor peer  152 ) due to the enforcement of cross-domain security policy. For example, the high side peers  112  may be hosted on a network with a different security classification than the low side peers  132 . Controls enforcing a cross-domain security policy may prevent the high side anchor peer  151  from relaying gossip messages from the high side domain  110  directly to the low side anchor peer  152  in the low side domain  130 . Instead, each of the high side domain anchor peer  151  and the low side domain anchor peer  152  may communicate gossip messages via the multi-domain relay  150 . Here, the multi-domain relay  150  can filter out and prevent data from spilling across the domains. 
     Furthermore, the high side domain anchor peer  151  cannot communicate gossip messages from the high side peers  112  to the multi-domain relay  150 . Rather, the gossip messages that are sent from the high side domain anchor peer  151  to the multi-domain relay  150  must originate on the high side domain anchor peer  151  and be based on the state of its own instance of the blockchain ledger. Likewise, the low side domain anchor peer  152  cannot communicate gossip messages from the low side peers  132  to the multi-domain relay  150 . Rather, the gossip messages transmitted by the low side domain anchor peer  152  to the multi-domain relay  150  must originate on the low side domain anchor peer  151  and be based on the state of its own instance of the blockchain ledger. 
     According to various embodiments, the multi-domain relay  150  may replace an existing, update, or otherwise add a new endpoint into the gossip message. For example, a gossip message received from the high side domain anchor peer  151  may include an endpoint of the multi-domain relay  150 . Here, the multi-domain relay  150  may update or otherwise replace the endpoint with an endpoint of the low side domain anchor peer  152  and route the gossip message to the low side domain anchor peer  152  based on the changed endpoint. In this example, the endpoint may include a network address, URL, peer ID, or other identifier. In addition, the multi-domain relay  150  may inspect the content of the gossip message to ensure that the data does not violate a cross-domain security policy. Likewise, the multi-domain relay  150  may replace an endpoint in a gossip message from the low side domain anchor peer  152  with an endpoint of the high side domain anchor peer  151 , and route the gossip message to the high side domain anchor peer  152 . Extra controls may be added to the high side domain anchor peer  151  and the low side domain anchor peer  152  to perform gossip with the multi-domain relay  150  without knowing the endpoint of the respective far-side anchor peer. 
     In these examples, only the domain anchor peers  151  and  152  may communicate with the multi-domain relay  150 . However, each of the domain anchor peers  151  and  152  may communicate with peer nodes on their respective side. Thus, the high side domain anchor peer  151  can maintain a high side ledger just as the high side blockchain peers  112 . Likewise, the low side domain anchor peer  152  can maintain a low side ledger just as the low side blockchain peers  132 . The exception of the gossip messages transmitted by the domain anchor peer and the respective peer nodes is that the channel membership information may be removed when the gossip message is originated and transmitted from the domain anchor peers  151  and  152  to the multi-domain relay  150 . The channel membership information may be removed by the respective domain anchor peers  151  and  152  or the multi-domain relay  150 . 
     Each of the domain anchor peers  151  and  152  may be triggered to transmit gossip messages after every commit made to its own ledger. Thus, the high side domain anchor peer  151  may transmit a gossip message (with updated blockchain state data) to the multi-domain relay  150  each time the high side ledger is updated by the high side domain anchor peer  151 , and vice versa. Thus, blockchain ledgers may remain identical even when separated by different security domains. As another example, each of the domain anchor peers  151  and  152  may be triggered to transmit a gossip message (with current blockchain state data) to the multi-domain relay  150  when requested by a far side domain anchor peer via the multi-domain relay  150 . In addition, the domain anchor peers  151  and  152  may also send out alive messages to respective blockchain peers on their side to maintain channel membership information. 
       FIG.  2 A  illustrates a blockchain architecture configuration  200 , according to example embodiments. Referring to  FIG.  2 A , 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.  2 A  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 code 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.  2 B  illustrates an example of a blockchain transactional flow  250  between nodes of a single-domain blockchain in accordance with an example embodiment. The example of  FIG.  2 B  does not include the embodiments required for a multi-domain blockchain network. Referring to  FIG.  2 B , 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 . 
     The example of the transactional flow  250  of  FIG.  2 B  corresponds to a single client submitting a transaction to a blockchain network for endorsement. According to various embodiments, the transactional flow  250  shown in  FIG.  2 B  may be performed by different clients independently for the same physical transaction. In other words, the transactional flow  250  is between one client and the blockchain network, but it may be performed by multiple clients. 
     Referring again to  FIG.  2 B , 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 endorsing peers signatures 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 peers 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.  3 A  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.  3 B  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.  3 C  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.  3 C , 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 . 
       FIG.  4 A  illustrates a process  400 A of gossip exchange between a domain anchor peer  410  and a multi-domain relay  420  according to example embodiments. Referring to  FIG.  4 A , the domain anchor peer  410  communicates via gossip protocol with a plurality of same side blockchain peers  411 ,  412 , and  413 , through the exchange of gossip messages. For example, the gossip messages may include channel membership information, blockchain content/state information, alive information, and the like. The domain anchor peer  410  is hosted within a security domain (e.g., the high side domain) and prevents non-trusted peers from gossiping across boundaries. 
     However, the domain anchor peer  410  is considered a trusted node with respect to the multi-domain relay  420  because the domain anchor peer  410  implements the same high assurance security controls as the multi-domain relay  420 . Thus, the multi-domain relay  420  and the domain anchor peer  410  can communicate securely with one another. Furthermore, the domain anchor peer  410  is the only external connection point between the blockchain peers  411 ,  412 , and  413 , and the multi-domain relay  420 . Accordingly, the domain anchor peer  410  serves as an anchor point between the near side (high side) and the far side (low side security domain). The domain anchor peer  410  may be a high availability component. The domain anchor peer  410  may receive, validate, and reconcile blockchain state (blocks in the chain and world state database) with gossip from the blockchain peers  411 ,  412 , and  413 . However, the domain anchor peer  410  does not forward gossip messages received from  411 ,  412 , and  413  to the far side (i.e., the low side in this example) to protect against spillage/malicious content across the boundary. 
     In addition, the domain anchor peer  410  can receive, validate, and reconcile blockchain ledger state with gossip messages from a (trusted) far-side domain anchor peer via the multi-domain relay  420 . For example, as shown in  FIG.  4 B , the domain anchor peer  410  corresponds to the high side domain anchor peer, and the domain anchor peer  430  corresponds to the low side domain anchor peer (far side with respect to the domain anchor peer  410 ). In this example, the high side domain anchor peer  410  and the low side domain anchor peer  430  may communicate self-originated gossip messages with the multi-domain relay  420  to ensure that far-sided blockchain state remains consistent. Furthermore, the multi-domain relay  420  may enforce a cross-domain security policy including content validation of gossip messages to prevent spillage or malicious content passing across domain boundaries. For example, the multi-domain relay  420  may inspect the content of the gossip messages before sending the gossip messages from one side of the network to the other to ensure that sensitive/restricted data is not being transferred. 
     The multi-domain relay  420  provides a controlled interface for secure propagation of peer gossip messages between network nodes located on different security domains. The multi-domain relay  420  may apply and enforce operating-system-level security controls to protect hosted component processes and isolate inter-connected domains. The multi-domain relay  420  may prevent any direct domain-to-domain (i.e., inter-domain) communication. The multi-domain relay  420  may enforce domain-wide security policies including content classification. The multi-domain relay  420  may ensure that prior to communicating across domain boundaries, every gossip message is inspected and validated/verified to ensure that the content therein satisfies a cross-domain sharing policy and that no channel membership information is included therein. Furthermore, the multi-domain relay  420  may only connect to domain anchor nodes and may not accept any connection from other blockchain peers. 
       FIG.  4 B  illustrates a process  400 B of exchanging gossip content between different domains in a blockchain network according to example embodiments. Referring to  FIG.  4 B , the high side domain anchor peer  410  performs gossip with same sided (high side) blockchain peers  412 . The high side domain anchor peer  410  manages its own version of a blockchain ledger including a blockchain and state database which is shared/replicated with the same sided blockchain peers  412 . Likewise, a low side domain anchor peer  430  performs gossip with same sided (low side) blockchain peers  432 . The low side domain anchor peer  430  manages its own version of a blockchain ledger including a blockchain and a state database shared/replicated with the same sided blockchain peers  432 . 
     In this example, both the high side and the low side share in a blockchain ledger without communicating with one another. Thus, the blockchain ledgers maintained by the high sided blockchain peers  412  (including the high side domain anchor node  410 ) and the blockchain ledgers maintained by the low sided blockchain peers  432  (including the low side domain anchor peer  430 ) should be the same. However, the blockchain ledger content can become inconsistent over time. To ensure that the content/state of the respective blockchain ledger are the same, the multi-domain relay  420  may enable gossip messages to be exchanged between the two sides without channel membership information of each side being exchanged. 
     For example, the high side domain anchor peer  410  may create a gossip message  415 A with its own state content (e.g., block content, block numbers, block hashes, transaction data, transaction hashes, timestamps, etc.) created by gossiping and reconciliation with the high side blockchain peers  412 . The gossip message  415 A may be transmitted from the high side domain anchor peer  410  to the multi-domain relay  420 . Here, the high side domain anchor peer  410  may be unaware of an endpoint of the low side domain anchor peer  430 . The multi-domain relay  420  may change the endpoint or otherwise add the endpoint of the low side domain anchor peer  430  into the gossip message  415 A to create gossip message  415 B. The multi-domain relay  420  may also ensure that the gossip message  415 A/ 415 B does not include content that violates a cross-domain data sharing policy. Upon successful verification, the multi-domain relay  420  may transfer the gossip message  415 B to the low side domain anchor peer  430 . 
     The low side domain anchor peer  430  may create a gossip message  435 A with its own state content (e.g., block content, block numbers, block hashes, transaction data, transaction hashes, timestamps, etc.) created by gossiping and reconciliation with the low side blockchain peers  432 . The gossip message  435 A may be transmitted from the low side domain anchor peer  430  to the multi-domain relay  420 . Here, the low side domain anchor peer  430  may be unaware of an endpoint of the high side domain anchor peer  410 . The multi-domain relay  420  may change the endpoint or otherwise add the endpoint of the high side domain anchor peer  410  into the gossip message  435 A to create gossip message  435 B. The multi-domain relay  420  may also ensure that the gossip message  435 A/ 435 B does not include content that violates a cross-domain data sharing policy. Upon successful verification, the multi-domain relay  420  may transfer the gossip message  435 B to the high side domain anchor peer  410 . 
       FIG.  5    illustrates a method  500  of synchronizing state among different security domains according to example embodiments. As a non-limiting example, the method  500  may be performed by a multi-domain relay node in a multi-domain blockchain network, and the like. Referring to  FIG.  5   , in  510 , the method may include receiving a gossip message from a domain anchor peer in a first security domain. The gossip message may include blockchain state information of a domain anchor peer blockchain ledger managed by a plurality of nodes in the first security domain. The blockchain state information may include block content such as block hashes, hashed transaction content, block numbers, timestamps, chaincode information, read-write sets, and the like. 
     In  520 , the method may include verifying that block content within the gossip message does not violate a cross-domain security policy. For example, the cross-domain security policy may identify data which cannot pass from the first security domain to the second security domain. In some embodiments, the cross-domain security policy may identify data which is allowed for storage in the first and second security domains. In response to verifying the block content does not violate the cross-domain security policy, in  530 , the method may include updating an endpoint of the gossip message with an address of a domain anchor peer in a second security domain. In  540 , the method may include transmitting the updated gossip message to the domain anchor peer in the second security domain. 
     In some embodiments, the first security domain may include a high side of a blockchain network and the second security domain comprises a low side of the blockchain network, where the low side is logically and physically isolated from the high side. For example, the logical isolation may be implemented at the operating system level preventing access to peer nodes on a far side of the blockchain network. In some embodiments, the method may further include verifying that channel membership information of the first security domain is not included within the gossip message prior to transmitting the updated gossip message to the domain anchor peer in the second security domain. In some embodiments, the method may further include receiving a request to transmit the gossip message from the domain anchor peer in the second security domain, and transmitting the request to the domain anchor peer in the first security domain. 
       FIG.  6 A  illustrates an example system  600  that includes a physical infrastructure  610  configured to perform various operations according to example embodiments. Referring to  FIG.  6 A , 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.  6 B  illustrates another example system  640  configured to perform various operations according to example embodiments. Referring to  FIG.  6 B , 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.  6 C  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.  6 C , 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.  6 D  illustrates a system  660  including a blockchain, according to example embodiments. Referring to the example of  FIG.  6 D , 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.  7 A  illustrates a process  700  of a new block being added to a distributed ledger  720 , according to example embodiments, and  FIG.  7 B  illustrates contents of a new data block structure  730  for blockchain, according to example embodiments. Referring to  FIG.  7 A , 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.  7 B . The linking of the blocks (shown by arrows in  FIG.  7 A ) 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.  7 A , 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.  7 B , 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.  7 B  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.  7 A ) 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. 
     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.  7 C  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.  7 C , 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.  7 D  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 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.  8 A and  8 B  illustrate additional examples of use cases for blockchain which may be incorporated and used herein. In particular,  FIG.  8 A  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.  8 A , 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.  8 B  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.  8 B , 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.