Patent Publication Number: US-11030217-B2

Title: Blockchain implementing cross-chain transactions

Description:
TECHNICAL FIELD 
     This application generally relates to partitioning transaction data across multiple blockchains, and more particularly, relates to a blockchain implementing cross-chain transactions. 
     BACKGROUND 
     A ledger is commonly defined as an account book of entry, in which transactions are recorded and visible to authorized users. A distributed ledger is ledger that is replicated in whole or in part to multiple computing system. One type of distributed ledger is a cryptographic distributed Ledger (CDL) which can have at least some of these properties: irreversibility (once a transaction is recorded, it cannot be reversed), accessibility (any party can access the CDL in whole or in part), chronological and time-stamped (all parties know when a transaction was added to the ledger), consensus based (a transaction is added only if it is approved, typically unanimously, by parties on the network), verifiability (all transactions can be cryptographically verified). A blockchain is an example of a CDL. While the description and figures herein are described in terms of a blockchain, the instant application applies equally to any CDL. 
     The distributed ledger is a continuously growing list of records that typically apply cryptographic techniques such as storing cryptographic hashes relating to other blocks. Although, primarily used for financial transactions, a blockchain can store other assets such as information related to goods and services (i.e., products, packages, status, software, data, etc.). A decentralized scheme provides authority and trust to a decentralized network and enables its nodes to continuously and sequentially record their transactions on a public “block”, creating a unique “chain” referred to as a blockchain. Cryptography, via hash codes, is used to secure an authentication of a transaction source and removes a central intermediary. Furthermore, each block contains a timestamp and a link to a previous block thereby creating a tamper-proof chain of transaction history. Because a blockchain is a distributed system, before adding a transaction to a blockchain ledger, peers need to reach a consensus status. 
     Limited transaction throughput and storage are widely understood problems of blockchain technology. Certain technologies have made attempts to improve transaction throughput. For example, a blockchain in Bitcoin uses a proof of work consensus method that is easy to verify but which is computationally expensive (by design) and requires solving a cryptographic puzzle in the process. As another example, permissioned blockchains use consensus methods based on variants of byzantine fault-tolerant (BFT) state machines. These BFT state machines are chosen to provide higher transaction throughput and lower consensus latency but still do not provide the throughput necessary for many industries. That is, even with these improvements, current blockchain technology is not suited for large-scale data processing workloads commonly found in real-world applications for finance, insurance, software development, supply chain, transportation industry, and many others. As such, what is needed is a mechanism for expanding the throughput of a blockchain. 
     SUMMARY 
     One example embodiment may provide a method that includes one or more of storing, via a master chain, partition information that links together storage across a plurality of blockchains, receiving a request to execute a blockchain transaction from a client, determining whether the blockchain transaction is associated with data stored on one blockchain or data stored separately on different blockchains based on the partition information stored on the master chain, and, in response to a determination that the blockchain transaction is associated with data stored separately on different blockchains, identifying, via the master chain, a location of each blockchain from among the different blockchains and transmitting the locations to a system configured to perform the blockchain transaction. 
     Another example embodiment may provide a system that includes a storage configured to store, via a master chain, partition information that links together storage across a plurality of blockchains, and a processor configured to perform one or more of receive a request to execute a blockchain transaction from a client, determine whether the blockchain transaction is associated with data stored on one blockchain or data stored separately on different blockchains based on the partition information stored on the master chain, and in response to a determination that the blockchain transaction is associated with data stored separately on different blockchains, identify, via the master chain, a location of each blockchain from among the different blockchains and transmit the locations to a system configured to perform the blockchain transaction. 
     A further example embodiment may provide a non-transitory computer readable medium comprising instructions, that when read by a processor, cause the processor to perform one or more of storing, via a master chain, partition information that links together storage across a plurality of blockchains, receiving a request to execute a blockchain transaction from a client, determining whether the blockchain transaction is associated with data stored on one blockchain or data stored separately on different blockchains based on the partition information stored on the master chain, and, in response to a determination that the blockchain transaction is associated with data stored separately on different blockchains, identifying, via the master chain, a location of each blockchain from among the different blockchains and transmitting the locations to a system configured to perform the blockchain transaction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating a system for managing cross-chain transactions, according to example embodiments. 
         FIG. 2  is a diagram illustrating a peer node blockchain architecture configuration, according to example embodiments. 
         FIG. 3  is a diagram illustrating a permissioned blockchain network, according to example embodiments. 
         FIG. 4A  is a diagram illustrating a process of a master chain managing data partitioning across a plurality of partition blockchains according to example embodiments. 
         FIG. 4B  is a diagram illustrating a process of a mixed chain executing a cross-chain transaction based on data from a plurality of partition blockchains according to example embodiments. 
         FIGS. 5A and 5B  are diagrams illustrating methods of managing cross-chain transactions, according to example embodiments. 
         FIG. 6A  is a diagram illustrating a physical infrastructure configured to perform various operations on the blockchain in accordance with one or more operations described herein, according to example embodiments. 
         FIG. 6B  is a diagram illustrating a smart contract configuration among contracting parties and a mediating server configured to enforce smart contract terms on a blockchain, according to example embodiments. 
         FIG. 7  is a diagram illustrating a computer system configured to support 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 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 in any suitable manner in one or more embodiments. 
     In addition, while the term “message” may have been used in the description of embodiments, the application may be applied to many types of network data, such as, packet, frame, datagram, etc. The term “message” also includes packet, frame, datagram, and any equivalents thereof. Furthermore, while certain types of messages and signaling may be depicted in exemplary embodiments they are not limited to a certain type of message, and the application is not limited to a certain type of signaling. 
     The example embodiments are directed to methods, devices, networks and/or systems, which support a master blockchain system. The system includes a network of blockchains including a master blockchain that performs the role of an orchestrator or transaction router among the blockchains, a set of partition blockchains that store partitioned data. Furthermore, the system includes a mixed blockchain chain that retrieves data from multiple blockchains and executes cross-chain transactions by leveraging the data from the multiple blockchains. Some of the benefits of blockchain system is that it improves the capacity of a blockchain-based system in terms of both storage and transaction throughput. Specifically, in comparison to a single blockchain network, multiple (partitioned) blockchain networks can offer a much larger storage capacity (in aggregation) to store transaction data, and can further support a much greater number of concurrent transactions submitted from an application. 
     Blockchain is different from a traditional database in that blockchain is not a central storage but rather a decentralized, immutable, and secure storage, where nodes must share in changes to records in the storage. Some properties that are inherent in blockchain and which help implement the blockchain include, but are not limited to, an immutable ledger, smart contracts, security, privacy, decentralization, consensus, endorsement, accessibility, and the like. 
     According to various aspects, the partitioning function and the cross-chain execution function are implemented by newly defined smart contracts which are inherent and unique to blockchain. Furthermore, the example embodiments also provide a system-based transaction router smart contract that is configured to manage partitioning of data among a plurality of blockchains via access to system resources such as a network interface, etc. In response to receiving a request to execute a transaction, the transaction router smart contract (of the master chain) may identify multiple different blockchains having data for performing a transaction and provide locations of the different blockchains to the cross-chain handling smart contract (of the mixed chain). The cross-chain handling smart contract may retrieve the data from the different blockchains, execute the cross-chain transaction, and update the different blockchains based on the result of the cross-chain transaction. 
     Furthermore, additional blockchain attributes such as consensus, endorsement, and decentralized/distributed nodes are responsible for implementing the technical effect of the partition rule that determines which partitions (individual blockchains) to route an incoming transaction. Specifically, a consensus of participants (nodes) in the master blockchain may agree upon a common partitioning rule which can be used by the transaction router smart contract to route incoming transactions to appropriate partition chains. In one example, a single-chain transaction is simply routed to the respective partition chain where the data is stored. As another example, when a transaction involves data from multiple partition chains, the transaction may be routed to the mixed chain blockchain including the cross-chain handler which can retrieve the data and execute the cross-chain transaction. In some embodiments, the mixed-chain may also maintain its own blockchain having stored therein a hash-linked immutable record of cross-chains transactions. 
     The example embodiments provide numerous benefits over a traditional database. For example, through the network of blockchains the embodiments provide increased throughput and storage availability while also maintaining the level of trust and accountability required by a blockchain. Meanwhile, a traditional database could not be used to implement the example embodiments because a traditional database does not provide for consensus among nodes and thereby would rely on a single actor to decide how to partition the database. In this way, the single actor could change the partitioning scheme at their will and not based on an agreed upon consensus required by the master chain. Furthermore, the traditional database does not perform blockchain-based transactions where proof of transactions are stored on an immutable ledger that is only modifiable through consensus and endorsements. 
     In traditional database, data partitioning is typically employed to combat against data scalability, data isolation as well as transaction throughput issues within the database. Furthermore, newer storing technologies such as blockchain continue to have similar issues. In particular, with the growing interest in using permissioned blockchain (e.g., Hyperledger Fabric) to hold a transaction history of a business network, the business network faces the same technological barriers. At present, none of the current blockchain technologies have proposed a viable solution to scale transaction throughput of a blockchain via partitioning data across multiple blockchains. This is because, data partitioning is not a trivial solution for blockchain based applications and there are several technological challenges that need to be solved. For example, because blockchain maintains data immutability and trust using consensus among various parties, data partitioning also needs to provide the same level of trust, accountability as well as traceability. To address this issue, when data is partitioned into multiple blockchains, the system described herein may support “cross-chain” transactions thereby adapting to business networks that evolve over time. Furthermore, the system may partition data across multiple blockchains in order to support data partitioning as well as cross-chain transactions while maintaining trust, accountability and traceability. In particular, the blockchain system is able to (a) partition data across multiple blockchains; (b) support cross-chain transactions and (c) maintain trust, provenance and traceability. 
     The instant application in one embodiment relates to partitioning transaction data across multiple blockchains, and in another embodiment relates to a blockchain implementing cross-chain transactions. 
       FIG. 1  illustrates a system  100  of blockchains for managing cross-chain transactions, according to various example embodiments. Referring to  FIG. 1 , the system  100  includes a master chain network  110  (master chain), a mixed chain network  120  (mixed chain), and a plurality of partition blockchain networks. The blockchain networks may be connected to each other via a network  140  such as a private network, the Internet and/or the like. The system  100  may use a combination of blockchains in order to store transactions relevant to the partitioned data model in a business network, hence supporting scalability of the business network which can both increase storage capacity and transaction throughput dynamically over time as more storage is needed and/or transaction data grows. Overall, the proposed system includes the master chain  110  for routing incoming transactions and queries to appropriate partitions (i.e., mixed chain  120  or partition chains  132 - 136 ) where they can be processed. Meanwhile, the partitioned chains  132 - 136  are each responsible for maintaining data in a partition of the entire data domain. Furthermore, the mixed chain  120  may handle transactions that access data across multiple partitions. 
     The master chain  110  is the mechanism to route transactions based on a policy that is trusted by every party in the network. If a centralized router were used instead, the trustworthiness of the whole system would depend on this single entity which does not satisfy the requirements of blockchain. Therefore, the master chain  110  may persist and track changes in the partition rules via a blockchain including a chain of blocks hash-linked together. Once a partitioning policy is stored in the blockchain of the master chain  110 , individual blockchain nodes in the master chain  110  may route transactions to other different blockchain networks (e.g., mixed chain  120 , partitioned chains  132 - 136 , etc.) based on the partition rules stored in the master chain. The partitioning rules/information stored by the master chain  110  may include data ranges allocated to each of the different partitioned chains  132 ,  134 , and  136 , which identifies data stored at each partitioned chain. Furthermore, the master chain  110  may store network endpoints of each of the partitioned chains  132 ,  134 , and  136 , enabling data to be retrieved from one or more nodes of the partitioned chains  132 ,  134 , and  136 . 
     According to various aspects, the master chain  110  may receive a request to process a transaction involving distinct data stored in several different blockchains, which is referred to herein as a cross-chain transactions. One option for handling a cross-chain transaction is to migrate data from several chains to a particular chain and then execute the transaction on that chain. However, this approach is not a feasible solution because it would introduce unnecessary delay and instability in the network. Instead, the system  100  includes the mixed chain  120  which handles cross-chain transactions provided from the master chain  110  by accessing data from different blockchains and creating transactions involving the different chains of data to create a mixing of transaction data among the different chains. 
     The transaction data may be partitioned across multiple partitioned blockchains  132 ,  134 , and  136 . The master chain  110  may identify locations of the data efficiently from these blockchains by building up an index based on a querying smart contract. For example, the querying may provide the master chain  110  with a location of transaction data that has not been accessed prior. Furthermore, the actual routing module, although it uses the partition rule stored in the master chain  110 , needs to be trusted. Therefore, the routing module (i.e., transaction router) may be integrated with blockchain node software. For example, the routing module may be implemented via a special type of smart contract/chaincode such as system chaincode available in Hyperledger Fabric 1.0, for example. The system chaincode may be an integrated part of a blockchain software module. In contrast with a typical smart contract that accesses on-chain data, the system smart contract may be designed to have system level access, which otherwise is not available to traditional smart contract that is supposed to run in a sandbox. 
       FIG. 2  illustrates a blockchain architecture configuration  200  of a blockchain, according to example embodiments. The configuration  200  may be an example of a traditional blockchain such as partitioning blockchains shown in  FIG. 1 . Referring to  FIG. 2 , 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  ( 4  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 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 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  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, transaction data  226  may be processed by one or more processing entities (e.g., virtual machines) included in the blockchain layer  216 . The transaction data  226  may include a hash-linked chain of data blocks which link together transactions executed via the blockchain. For example, a most recent transaction may be stored in a tail block of the blockchain. A transaction result  228  may include transaction data  226  mixed with data from another blockchain via a cross-chain transaction. The physical infrastructure  214  may be utilized to retrieve any of the data or information described herein. 
     Within chaincode, 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 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 of a smart contract, with additional features. 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 receives a hash and retrieves 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. In  FIG. 2 , the chaincode may introduce modifications to an asset via storage of data blocks representing results of executing a transaction. One function may be to add new values to the asset, change values of the asset, delete values of the asset, and the like, which may be distributed to and stored by one or more of the nodes  204 - 210 . 
     A client may transmit a request to execute a blockchain transaction (e.g., a cross-chain transaction) and may include an application leveraging a supported software development kit (SDK), such as NODE, JAVA, PYTHON, and the like, which utilizes an available application programming interface (API) to generate a cross-chain transaction proposal. The proposal is a request to invoke a chaincode function so that data can be read and/or written to the ledger or multiple ledgers of different blockchains (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. 
     The chaincode may be 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. Rather, the set of values, along with an endorsing peer node&#39;s signature may be passed back as a proposal response to the SDK of the client which parses the payload for the application to consume. 
     In response, the application of the client inspects/verifies the endorsing peer&#39;s 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. If the client application intends to submit the transaction to the ordering node service 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, the client assembles endorsements into a transaction and broadcasts the transaction proposal of the asset and response within a transaction message to the ordering node. The transaction may contain the read/write sets, the endorsing peer&#39;s signatures, and a channel ID. The ordering node does not need to inspect the entire content of a transaction in order to perform its operation, instead the ordering node may simply receive transactions from all channels in the network, order them chronologically by channel, and create blocks of transactions per channel. 
       FIG. 3  illustrates an example of a permissioned blockchain network  300  of a single blockchain, which features a distributed, decentralized peer-to-peer architecture, and a certificate authority  318  managing user roles and permissions. Any of the master chain, the mixed chain, and the partition chains may be a permissioned blockchain network  300 . In this example, the blockchain user  302  may submit a transaction to the permissioned blockchain network  310 . The transaction can be a deploy, invoke or query, and may be issued through a client-side application leveraging an SDK, directly through a REST API, or the like. Trusted business networks may provide access to regulator systems  314 , such as auditors (the Securities and Exchange Commission in a U.S. equities market, for example). Meanwhile, a blockchain network operator system of nodes  308  manage member permissions, such as enrolling the regulator system  310  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 system  316  writes chaincode and client-side applications. The blockchain developer system  316  can deploy chaincode directly to the network through a REST interface. To include credentials from a traditional data source  330  in chaincode, the developer system  316  could use an out-of-band connection to access the data. In this example, the blockchain user  302  connects to the network through a peer node  312 . Before proceeding with any transactions, the peer node  312  retrieves the user&#39;s enrollment and transaction certificates from the certificate authority  318 . In some cases, blockchain users must possess these digital certificates in order to transact on the permissioned blockchain network  310 . Meanwhile, a user attempting to drive chaincode may be required to verify their credentials on the traditional data source  330 . To confirm the user&#39;s authorization, chaincode can use an out-of-band connection to this data through a traditional processing platform  320 . 
       FIG. 4A  illustrates a process  400 A of a master chain  410  managing data partitioning across a plurality of partition blockchains according to example embodiments, and  FIG. 4B  illustrates a process  400 B of a mixed chain  420  executing a cross-chain transaction based on data from a plurality of partition blockchains according to example embodiments. Referring to  FIG. 4A , the master chain  410  manages a blockchain  412  that includes a hash-linked chain of blocks of partitioning information about how data is partitioned among the different partition blockchains  432 ,  434 , and  436 . The entire domain may be split into sub-domains or subsets where each partition blockchain  432 ,  434 , and  436  includes a unique sub-domain or subset that is exclusive of the other partition blockchains. Furthermore, the blockchain  412  may store information identifying network locations (e.g., endpoints, URLs, etc.) of a node of each partition blockchain  432 ,  434 , and  436  for retrieving and providing transaction data. 
     For example, the functionality of the master chain  410  may be implemented via three corresponding smart contracts. In one example, a partitioner smart contract  414  maintains a consensus among parties (master chain nodes) on a partitioning function that determines how the entire data domain can be partitioned, e.g., range boundaries of data maintained in each partition of the data domains allocated to each partition blockchain  432 - 436 . The master chain  410  may also include a transaction router smart contract  416  that routes the incoming transactions to the appropriate chain that is responsible (according to the partitioning function) to process the transactions. For example, single-chain transactions may be routed directly to the single chain where the transaction data is stored. Meanwhile, cross-chain transactions may be routed to the mixed chain  420  for processing. Routing information may be identified from the partitioning information stored in the blockchain  412 . 
     The master chain  410  may also include a query federator smart contract  418  that is responsible for handling queries from the client. In some embodiments, the partitioner smart contract  414  may be a smart contract running inside each peer node in the master chain based on on-chain data, while the transaction router  416  and the query federator  418  may be special system smart contracts (aka system chaincode) that have the system level capability to access various other software components in the host node, which is however not available to a usual smart contract that runs inside a sandbox. Meanwhile, the partitioned blockchains  432 ,  434 , and  436 , may be traditional blockchain networks which maintain different partitions of the entire data domain without knowing the full domain. Each partitioned chain may run a single-chain handler’ smart contract that receives the transaction and query requests from the master chain  410  and executes these requests. 
     Referring to  FIG. 4B , the mixed chain  420  receives a cross-chain transaction from the master chain  410  and executes the cross-chain transaction. For example, the request received from the master chain  410  may include network locations of the blockchain networks that have data stored therein for the cross-chain transaction. Therefore, the mixed chain  420  can identify which partitioned blockchains among the plurality of partitioned blockchains  432 ,  434 , and  436 , that have data for the cross-chain transactions. The mixed chain  420  includes a cross-chain handler smart contract  424  that receives the transaction request from the master chain  41  and is responsible for accessing data across multiple partitions. Furthermore, the cross-chain handler  424  executes the cross-chain transaction thereby mixing data together from different partition blockchains to create a mixed result. The cross-chain handler  424  may store the results of the cross-chain transaction in a blockchain  422  which links together results of all cross-chain transactions performed in the system. Furthermore, the cross-chain handler  424  may also update the partition blockchains that provided data for the transaction with the results of the cross-chain transaction to enable the partition blockchains to update the data/assets stored therein. 
     According to various embodiments, the master chain  410  may be initialized with information of the endpoints of other blockchains ( 420 ,  432 ,  434 , and  436 ). Within the master chain  410 , each party in the network may come to a consensus of the partition rule off-network and one authorized party may invoke a “setPartitionRule” method in the partitioner smart contract  414  to set the partition rule in the blockchain  412 . Any changes to the partition rule are also stored in the blockchain  412  making them traceable. After initialization, the partitioner smart contract  414  may set an enable flag so that every node in this master chain is able to fetch the partition rule and route transactions according to that rule. Furthermore, the transaction router smart contract  416  may first identify which data is accessed by these transactions. For example, the transaction router  416  may look up the partitioning rule from the blockchain through the partitioner smart contract  414 . According to various embodiments, next, the transaction router  416  decides which blockchain network the transactions should be routed to. For example, if a transaction only accesses data within a single partition, then it will be routed to a particular partitioned blockchain network. On the contrary, transactions that access data in multiple partitions are routed to the mixed chain  420  network for processing. 
     Meanwhile, a workflow to process a transaction in the mixed chain  420  includes the cross-chain handler smart contract  424  receiving transactions and partition information from master chain&#39;s transaction router. In response, the cross-chain handler  424  fetches data from different chains, persists the fetched data as well as new values in its own chain  412 , and initiates a separate “setDiff” transaction to update the latest value for different parties in the different partitioned chains. For example, if balance of ‘X’ is fetched from ‘B-chain’  434  and balance of ‘Y’ is fetched from ‘A-chain’  432 , then after a balance transfer transactions from X to Y, the final balance differences of X and Y will be set using “setDiff” transaction in “B-chain” and vice versa. Thus the “mixed chain” will contain the cross-chain transactions, but also update the other relevant chains with a separate “setDiff” transaction to update the value by the delta changes. In some embodiments, if a cross-chain transaction is in process and there is a new incoming transaction that accesses some data common with the cross-chain transaction, this new transaction may be put on hold for a defined period of time or discarded immediately by the transaction router  416 . 
     As another example, if a query accesses data based on the partitioning attribute that is included in the partitioning function, then the query federator  418  just routes the query to the particular partitioned chain maintaining the data of interest. In contrast, if the query accesses data based on a non-partitioning attribute, the query federator  418  may not be aware of where the data is stored between the different blockchain partitions. In this case, the query federator  418  may forward the query to every partitioned chain and aggregate the results returned by these chains prior to returning to the client. 
     As described, the mixed chain  420  may perform transactions across the different partition blockchains  432 - 436 . For example, the transaction router  414  may read the user information contained in the incoming transaction and the partition rule maintained in its blockchain  412  (i.e., the master chain or partition smart contract). As a non-limiting example, the transaction router  414  may identify that the data record associated with user “U1” resides in partition A  432  whereas the data record associated with user “U2” resides in partition B  434 . In this example, the transaction router  414  may update its lock table with the information that a cross-chain transaction is in progress for “U1” and “U2.” Then this transaction may be forwarded to the mixed chain  420  with the detail of “U1”, “U2” and their blockchain node URLs. In response, the cross-chain handler  424  may fetch the data for “U1” from partition A  432  and the data for “U2” from partition B  434 . Furthermore, the cross-chain handler  424  may create a transaction in its own blockchain  422  and also send “SetDiff” transaction to U1&#39;s blockchain (partition A  432 ) with the delta of U1&#39;s balance and send a separate “SetDiff” transaction to U2&#39;s blockchain (partition B  434 ) with the delta of U2&#39;s balance. 
       FIG. 5A  illustrates a method  500  of routing a transaction for cross-chain processing, according to example embodiments. For example, the method  500  may be implemented via a smart contract executed by a blockchain node within a master blockchain network. As another example, the method  500  may be performed by a group of computing nodes within the master blockchain network. Referring to  FIG. 5A , in  510  the method may include storing, via a master chain, partition information that links together storage across a plurality of blockchains. For example, the partition information may include partition rules generated by a consensus of nodes of the master chain. The partition rules may identify ranges of data stored by each of a plurality of different blockchains as well as location information of each blockchain such as a uniform resource locator (URL) or the like. In some embodiments, the method may include establishing the partition information in response to detecting a consensus of the partition information from a plurality of blockchain nodes that manage the master chain. 
     In  520 , the method may include receiving a request to execute a blockchain transaction from a client. For example, the client may request a transaction that leverages data from a single blockchain or a transaction that leverages data from multiple different blockchains. In  530 , the method may include determining, via the master chain, whether the blockchain transaction is associated with data stored on one blockchain or data stored separately on different blockchains based on the partition information stored on the master chain. For example, the transaction may identify a particular asset or data item, and the partition information may identify where the asset or data item is stored based on a partitioner smart contract that manages the master chain and the partitioning information. 
     In response to a determination that the blockchain transaction is associated with data stored separately on different blockchains, in  540  the method may further include identifying, via the master chain, a location of each blockchain from among the different blockchains and transmitting the locations to a system configured to perform the blockchain transaction. In some embodiments, the transmitting may include transmitting the locations to a cross-chain handler smart contract executing on a mixed chain which is configured to retrieve respective data from each of the different blockchains and execute the blockchain transaction based on the data retrieved from the different blockchains. 
     In some embodiments, the partition information identifies an entire domain or range of transaction data managed by the master chain, and also identifies respective sub-domains allocated to each respective blockchain among the plurality of blockchains. Here, the partition information or sub-domain information may identify boundary ranges of transaction data maintained by each blockchain among the plurality of blockchains. 
     In some embodiments, the method may further include individually querying the plurality of blockchains to determine at least one blockchain storing data for the blockchain transaction, when the master chain does not include an identity of a blockchain storing the data for the blockchain transaction. For example, the querying may be performed by a query federator smart contract executing on the blockchain node, while the determining may be performed by a transaction routing smart contract executing on the blockchain node. In some embodiments, the method may further include detecting an enablement flag that has been set via the master chain and fetching the partition information in response to detection of the enablement flag. 
       FIG. 5B  illustrates a method  550  of executing a cross-chain transaction based on data from multiple blockchain networks, according to example embodiments. For example, the method  550  may be performed by a node of a mixed chain network. Referring to  FIG. 5B , in  551 , the method may include receiving a request to execute a cross-chain transaction. For example, the request may be received from a master chain that has identified a blockchain transaction that requires data from different blockchains. In  552 , the method may include identifying disparate locations of two or more different blockchains that have stored therein data for the cross-chain transaction. For example, the mixed chain may identify network locations of blockchain nodes registered for communication with the mixed chain and having location information (e.g., URL, endpoint, etc.) stored in the master chain. In this example, the identifying may include identifying different network locations for accessing the two or more different blockchains, respectively, based on two or more URLs included in the request. 
     In  553 , the method may include retrieving data from data blocks of the two or more different blockchains, respectively, based on the identified disparate locations. For example, the retrieving may include transmitting a request from the mixed chain to a blockchain node of each of the different blockchains requesting different data items (e.g. data ranges) of data that is stored on the different blockchains. Here, the data may be unique to each of the respective blockchains and not obtainable from the same blockchain. In  554 , the method may include executing the cross-chain transaction which takes the retrieved data from the two or more different blockchains as inputs to generate a cross-chain result. For example, the executing of the cross-chain transaction may cause the retrieved data from the two or more different blockchains to be mixed together such as through an exchange of data, a combination of data, a subtraction of data, an addition of data, a modification of data, and the like. 
     In  555 , the method may include storing the cross-chain result via a data block of a distributed ledger. For example, the storing may include inserting a new data block having stored therein information about the cross-chain result into each of the two or more different blockchains. In this example, the storing may include inserting a new data block having stored therein information about the cross-chain result into a first blockchain from among the two or more different blockchains to update transaction data obtained from the first blockchain with a delta value resulting from the cross-chain result. In some embodiments, the storing may include inserting a new data block having stored therein information about the cross-chain result into a mixed-chain blockchain based on the generated cross-chain result. In some embodiments, the storing further may include linking the new data block inserted into the mixed-chain blockchain to a cross-chain result of another cross-chain transaction previously stored in the mixed-chain blockchain. 
       FIG. 6A  illustrates an example physical infrastructure configured to perform various operations on the blockchain in accordance with one or more of the example methods of operation according to example embodiments. Referring to  FIG. 6A , the example configuration  600 A includes a physical infrastructure  610  with a blockchain  620  and a smart contract  640 , which may execute any of the operational steps  612  included in any of the example embodiments. For example, the smart contract  640  may execute transactions and invoke changes to multiple different blockchain ledgers as a result of a cross-chain transaction being executed thereby updating a world state of multiple blockchains at the same time (i.e., simultaneously). In this example, the steps/operations  612  may include one or more of the steps described or depicted in one or more flow diagrams and/or logic diagrams. The steps may represent output or written information that is written or read from one or more smart contracts  640  and/or blockchains  620  that reside on the physical infrastructure  610  of a computer system configuration. The data can be output from an executed smart contract  640  and/or blockchain  620 . The physical infrastructure  610  may include one or more computers, servers, processors, memories, and/or wireless communication devices. 
       FIG. 6B  illustrates an example 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. 6B , the configuration  650 B may represent a communication session, an asset transfer session or a process or procedure that is driven by a smart contract  640  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  640  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 as a blockchain transaction. 
     Examples of smart contracts include normal smart contracts which execute decisions based on data that is stored on-chain. For example, the partitioning smart contract of the master chain may identify and store partitioning rules via a blockchain on the master chain. Another example of a smart contract is a system smart contract that is configured to access data and functionality of a computing system outside of the chain (also referred to as off-chain). For example, the transaction router may identify network information and interact with a network interface of the system to route transactions to single-partition blockchains or the mixed chain. As another example, the query federator may interact with network information and the network interface of the system to transmit queries to other blockchains systems and receive responses. 
     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. For example,  FIG. 7  illustrates an example computer system architecture  700 , which may represent or be integrated in any of the above-described components, etc. 
       FIG. 7  is not intended to suggest any limitation as to the scope of use or functionality of embodiments of the application described herein. Regardless, the computing node  700  is capable of being implemented and/or performing any of the functionality set forth hereinabove. 
     In computing node  700  there is a computer system/server  702 , 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  702  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  702  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  702  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. 7 , computer system/server  702  in cloud computing node  700  is shown in the form of a general-purpose computing device. The components of computer system/server  702  may include, but are not limited to, one or more processors or processing units  704 , a system memory  706 , and a bus that couples various system components including system memory  706  to processor  704 . 
     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  702  typically includes a variety of computer system readable media. Such media may be any available media that is accessible by computer system/server  702 , and it includes both volatile and non-volatile media, removable and non-removable media. System memory  706 , in one embodiment, implements the flow diagrams of the other figures. The system memory  706  can include computer system readable media in the form of volatile memory, such as random-access memory (RAM)  710  and/or cache memory  712 . Computer system/server  702  may further include other removable/non-removable, volatile/non-volatile computer system storage media. By way of example only, storage system  714  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  706  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  716 , having a set (at least one) of program modules  718 , may be stored in memory  706  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  718  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  702  may also communicate with one or more external devices  720  such as a keyboard, a pointing device, a display  722 , etc.; one or more devices that enable a user to interact with computer system/server  702 ; and/or any devices (e.g., network card, modem, etc.) that enable computer system/server  702  to communicate with one or more other computing devices. Such communication can occur via I/O interfaces  724 . Still yet, computer system/server  702  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  726 . As depicted, network adapter  726  communicates with the other components of computer system/server  702  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  702 . 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. 
     According to various embodiments, in one example, the computing system  702  may be a blockchain node included within the master chain described herein. In this example, the memory  704  may store a master chain that includes partition information such as rules, URLs, and the like, which links together storage across a plurality of different blockchains. The processor  704  may receive a request to execute a blockchain transaction from a client, and may determine whether the blockchain transaction is associated with data stored on one single blockchain or data stored separately on different blockchains based on the partition information stored on the master chain. In response to a determination that the blockchain transaction is associated with data stored separately on different blockchains, the processor  704  may identify, via the master chain, a location of each blockchain from among the different blockchains and transmit the locations to a system such as the mixed chain which configured to perform the cross-chain blockchain transaction. 
     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.