Patent Publication Number: US-11640392-B2

Title: Blockchain endorsement agreement

Description:
BACKGROUND 
     Disclosed herein is a system and related method for utilizing a blockchain endorsement agreement. More particularly, the system and method process a smart contract using a pre-endorsement result that is associated with a transaction proposal. 
     SUMMARY 
     According to one aspect disclosed herein, a computer-implemented method uses a processor for processing a smart contract is provided to receive a transaction proposal (TP) from a blockchain client. The processor determines a pre-endorsement result (PER) that is associated with the TP, analyzes, according to a pre-endorsement agreement logic, the PER to produce an agreed result, and endorses the agreed result. The processor sends, to the blockchain client, the endorsed agreed result. 
     According to another aspect disclosed herein, a system is provided comprising a processor of an endorser peer node that is configured to receive a transaction proposal (TP) from a blockchain client, determine a pre-endorsement result (PER) that is associated with the TP, analyze, according to a pre-endorsement agreement logic, the PER to produce an agreed result, endorse the agreed result, and send, to the blockchain client, the endorsed agreed result. 
     According to another aspect disclosed herein, a computer program product is provided to implement the method and system described above. The computer program product contains instructions that are, accessible from a computer-usable or computer-readable medium providing program code for use, by, or in connection, with a computer or any instruction execution system. For the purpose of this description, a computer-usable or computer-readable medium may be any apparatus that may contain a mechanism for storing, communicating, propagating or transporting the program for use, by, or in connection, with the instruction execution system, apparatus, or device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various embodiments are described herein with reference to different subject-matter. In particular, some embodiments may be described with reference to methods, whereas other embodiments may be described with reference to apparatuses and systems. However, a person skilled in the art will gather from the above and the following description that, unless otherwise notified, in addition to any combination of features belonging to one type of subject-matter, also any combination between features relating to different subject-matter, in particular, between features of the methods, and features of the apparatuses and systems, are considered as to be disclosed within this document. 
       The aspects defined above, and further aspects disclosed herein, are apparent from the examples of one or more embodiments to be described hereinafter and are explained with reference to the examples of the one or more embodiments, but to which the invention is not limited. Various embodiments are described, by way of example only, and with reference to the following drawings: 
         FIG.  1 A  is a block diagram of a data processing system (DPS) according to one or more embodiments disclosed herein. 
         FIG.  1 B  is a pictorial diagram that depicts a cloud computing environment according to an embodiment disclosed herein. 
         FIG.  1 C  is a pictorial diagram that depicts abstraction model layers according to an embodiment disclosed herein. 
         FIG.  2 A  is a block diagram that illustrates an example blockchain architecture configuration, according to example embodiments. 
         FIG.  2 B  is a flow diagram that illustrates a blockchain transactional flow, according to example embodiments. 
         FIG.  3 A  is a block diagram that illustrates a permissioned network, according to example embodiments. 
         FIG.  3 B  is a block diagram that illustrates another permissioned network, according to example embodiments. 
         FIG.  3 C  is a block diagram that illustrates a permissionless network, according to example embodiments. 
         FIG.  4    is a block diagram that illustrates a basic blockchain sequence. 
         FIG.  5 A  is a block diagram that illustrates an example system configured to perform one or more operations described herein, according to example embodiments. 
         FIG.  5 B  is a block diagram that illustrates another example system configured to perform one or more operations described herein, according to example embodiments. 
         FIG.  5 C  is a block diagram that illustrates a further example system configured to utilize a smart contract, according to example embodiments. 
         FIG.  5 D  is a block diagram that illustrates yet another example system configured to utilize a blockchain, according to example embodiments. 
         FIG.  6 A  is a block diagram that illustrates a process for a new block being added to a distributed ledger, according to example embodiments. 
         FIG.  6 B  is a block diagram that illustrates contents of a new data block, according to example embodiments. 
         FIG.  6 C  is a block diagram that illustrates a blockchain for digital content, according to example embodiments. 
         FIG.  6 D  is a block diagram that illustrates a block which may represent the structure of blocks in the blockchain, according to example embodiments. 
         FIG.  7 A  is a block diagram that illustrates an example blockchain which stores machine learning (artificial intelligence) data, according to example embodiments. 
         FIG.  7 B  is a block diagram that illustrates an example quantum-secure blockchain, according to example embodiments. 
         FIG.  8    is a block diagram that illustrates a high-level block diagram of an example computer system that may be used in implementing one or more of the methods, tools, and modules, and any related functions, described herein, in accordance with embodiments of the present disclosure. 
         FIG.  9 A  is a block diagram of a smart contract system, according to some implementations. 
         FIG.  9 B  is a block diagram of a network smart contract system, according to some implementation. 
         FIG.  10 A  is a block diagrams illustrating the use of endorser peers with a trained model or service, according to some implementations. 
         FIG.  10 B  is a block flow diagram illustrating the use of endorser peers with a trained model or service, according to some implementations. 
         FIG.  11    is a flowchart illustrating a process for processing smart contracts, according to some implementations. 
     
    
    
     DETAILED DESCRIPTION 
     The following acronyms may be used below: 
     API application program interface 
     ARM advanced RISC machine 
     CD-ROM compact disc ROM 
     CMS content management system 
     CoD capacity on demand 
     CPU central processing unit 
     CUoD capacity upgrade on demand 
     DPS data processing system 
     DVD digital versatile disk 
     EPROM erasable programmable read-only memory 
     FPGA field-programmable gate arrays 
     HA high availability 
     IaaS infrastructure as a service 
     I/O input/output 
     IPL initial program load 
     ISP Internet service provider 
     ISA instruction-set-architecture 
     LAN local-area network 
     LPAR logical partition 
     PaaS platform as a service 
     PDA personal digital assistant 
     PLA programmable logic arrays 
     RAM random access memory 
     RISC reduced instruction set computer 
     ROM read-only memory 
     SaaS software as a service 
     SLA service level agreement 
     SRAM static random-access memory 
     WAN wide-area network 
     Data Processing System in General 
       FIG.  1 A  is a block diagram of an example DPS according to one or more embodiments. In this illustrative example, the DPS  10  may include communications bus  12 , which may provide communications between a processor unit  14 , a memory  16 , persistent storage  18 , a communications unit  20 , an I/O unit  22 , and a display  24 . 
     The processor unit  14  serves to execute instructions for software that may be loaded into the memory  16 . The processor unit  14  may be a number of processors, a multi-core processor, or some other type of processor, depending on the particular implementation. A number, as used herein with reference to an item, means one or more items. Further, the processor unit  14  may be implemented using a number of heterogeneous processor systems in which a main processor is present with secondary processors on a single chip. As another illustrative example, the processor unit  14  may be a symmetric multi-processor system containing multiple processors of the same type. 
     The memory  16  and persistent storage  18  are examples of storage devices  26 . A storage device may be any piece of hardware that is capable of storing information, such as, for example without limitation, data, program code in functional form, and/or other suitable information either on a temporary basis and/or a permanent basis. The memory  16 , in these examples, may be, for example, a random access memory or any other suitable volatile or non-volatile storage device. The persistent storage  18  may take various forms depending on the particular implementation. 
     For example, the persistent storage  18  may contain one or more components or devices. For example, the persistent storage  18  may be a hard drive, a flash memory, a rewritable optical disk, a rewritable magnetic tape, or some combination of the above. The media used by the persistent storage  18  also may be removable. For example, a removable hard drive may be used for the persistent storage  18 . 
     The communications unit  20  in these examples may provide for communications with other DPSs or devices. In these examples, the communications unit  20  is a network interface card. The communications unit  20  may provide communications through the use of either or both physical and wireless communications links. 
     The input/output unit  22  may allow for input and output of data with other devices that may be connected to the DPS  10 . For example, the input/output unit  22  may provide a connection for user input through a keyboard, a mouse, and/or some other suitable input device. Further, the input/output unit  22  may send output to a printer. The display  24  may provide a mechanism to display information to a user. 
     Instructions for the operating system, applications and/or programs may be located in the storage devices  26 , which are in communication with the processor unit  14  through the communications bus  12 . In these illustrative examples, the instructions are in a functional form on the persistent storage  18 . These instructions may be loaded into the memory  16  for execution by the processor unit  14 . The processes of the different embodiments may be performed by the processor unit  14  using computer implemented instructions, which may be located in a memory, such as the memory  16 . These instructions are referred to as program code  38  (described below) computer usable program code, or computer readable program code that may be read and executed by a processor in the processor unit  14 . The program code in the different embodiments may be embodied on different physical or tangible computer readable media, such as the memory  16  or the persistent storage  18 . 
     The DPS  10  may further comprise an interface for a network  29 . The interface may include hardware, drivers, software, and the like to allow communications over wired and wireless networks  29  and may implement any number of communication protocols, including those, for example, at various levels of the Open Systems Interconnection (OSI) seven layer model. 
       FIG.  1 A  further illustrates a computer program product  30  that may contain the program code  38 . The program code  38  may be located in a functional form on the computer readable media  32  that is selectively removable and may be loaded onto or transferred to the DPS  10  for execution by the processor unit  14 . The program code  38  and computer readable media  32  may form a computer program product  30  in these examples. In one example, the computer readable media  32  may be computer readable storage media  34  or computer readable signal media  36 . Computer readable storage media  34  may include, for example, an optical or magnetic disk that is inserted or placed into a drive or other device that is part of the persistent storage  18  for transfer onto a storage device, such as a hard drive, that is part of the persistent storage  18 . The computer readable storage media  34  also may take the form of a persistent storage, such as a hard drive, a thumb drive, or a flash memory, that is connected to the DPS  10 . In some instances, the computer readable storage media  34  may not be removable from the DPS  10 . 
     Alternatively, the program code  38  may be transferred to the DPS  10  using the computer readable signal media  36 . The computer readable signal media  36  may be, for example, a propagated data signal containing the program code  38 . For example, the computer readable signal media  36  may be an electromagnetic signal, an optical signal, and/or any other suitable type of signal. These signals may be transmitted over communications links, such as wireless communications links, optical fiber cable, coaxial cable, a wire, and/or any other suitable type of communications link. In other words, the communications link and/or the connection may be physical or wireless in the illustrative examples. 
     In some illustrative embodiments, the program code  38  may be downloaded over a network to the persistent storage  18  from another device or DPS through the computer readable signal media  36  for use within the DPS  10 . For instance, program code stored in a computer readable storage medium in a server DPS may be downloaded over a network from the server to the DPS  10 . The DPS providing the program code  38  may be a server computer, a client computer, or some other device capable of storing and transmitting the program code  38 . 
     The different components illustrated for the DPS  10  are not meant to provide architectural limitations to the manner in which different embodiments may be implemented. The different illustrative embodiments may be implemented in a DPS including components in addition to or in place of those illustrated for the DPS  10 . 
     Cloud Computing in General 
     It is to be understood that although this disclosure includes a detailed description on cloud computing, implementation of the teachings recited herein are not limited to a cloud computing environment. Rather, embodiments of the present invention are capable of being implemented in conjunction with any other type of computing environment now known or later developed. 
     Cloud computing is a model of service delivery for enabling convenient, on-demand network access to a shared pool of configurable computing resources (e.g., networks, network bandwidth, servers, processing, memory, storage, applications, virtual machines, and services) that can be rapidly provisioned and released with minimal management effort or interaction with a provider of the service. This cloud model may include at least five characteristics, at least three service models, and at least four deployment models. 
     Characteristics are as Follows 
     On-demand self-service: a cloud consumer can unilaterally provision computing capabilities, such as server time and network storage, as needed automatically without requiring human interaction with the service&#39;s provider. 
     Broad network access: capabilities are available over a network and accessed through standard mechanisms that promote use by heterogeneous thin or thick client platforms (e.g., mobile phones, laptops, and PDAs). 
     Resource pooling: the provider&#39;s computing resources are pooled to serve multiple consumers using a multi-tenant model, with different physical and virtual resources dynamically assigned and reassigned according to demand. There is a sense of location independence in that the consumer generally has no control or knowledge over the exact location of the provided resources but may be able to specify location at a higher level of abstraction (e.g., country, state, or datacenter). 
     Rapid elasticity: capabilities can be rapidly and elastically provisioned, in some cases automatically, to quickly scale out and rapidly released to quickly scale in. To the consumer, the capabilities available for provisioning often appear to be unlimited and can be purchased in any quantity at any time. 
     Measured service: cloud systems automatically control and optimize resource use by leveraging a metering capability at some level of abstraction appropriate to the type of service (e.g., storage, processing, bandwidth, and active user accounts). Resource usage can be monitored, controlled, and reported, providing transparency for both the provider and consumer of the utilized service. 
     Service Models are as Follows 
     Software as a Service (SaaS): the capability provided to the consumer is to use the provider&#39;s applications running on a cloud infrastructure. The applications are accessible from various client devices through a thin client interface such as a web browser (e.g., web-based e-mail). The consumer does not manage or control the underlying cloud infrastructure including network, servers, operating systems, storage, or even individual application capabilities, with the possible exception of limited user-specific application configuration settings. 
     Platform as a Service (PaaS): the capability provided to the consumer is to deploy onto the cloud infrastructure consumer-created or acquired applications created using programming languages and tools supported by the provider. The consumer does not manage or control the underlying cloud infrastructure including networks, servers, operating systems, or storage, but has control over the deployed applications and possibly application hosting environment configurations. 
     Infrastructure as a Service (IaaS): the capability provided to the consumer is to provision processing, storage, networks, and other fundamental computing resources where the consumer is able to deploy and run arbitrary software, which can include operating systems and applications. The consumer does not manage or control the underlying cloud infrastructure but has control over operating systems, storage, deployed applications, and possibly limited control of select networking components (e.g., host firewalls). 
     Deployment Models are as Follows 
     Private cloud: the cloud infrastructure is operated solely for an organization. It may be managed by the organization or a third party and may exist on-premises or off-premises. 
     Community cloud: the cloud infrastructure is shared by several organizations and supports a specific community that has shared concerns (e.g., mission, security requirements, policy, and compliance considerations). It may be managed by the organizations or a third party and may exist on-premises or off-premises. 
     Public cloud: the cloud infrastructure is made available to the general public or a large industry group and is owned by an organization selling cloud services. 
     Hybrid cloud: the cloud infrastructure is a composition of two or more clouds (private, community, or public) that remain unique entities but are bound together by standardized or proprietary technology that enables data and application portability (e.g., cloud bursting for load-balancing between clouds). 
     A cloud computing environment is service oriented with a focus on statelessness, low coupling, modularity, and semantic interoperability. At the heart of cloud computing is an infrastructure that includes a network of interconnected nodes. 
     Referring now to  FIG.  1 B , illustrative cloud computing environment  52  is depicted. As shown, cloud computing environment  52  includes one or more cloud computing nodes  50  with which local computing devices used by cloud consumers, such as, for example, personal digital assistant (PDA) or cellular telephone  54 A, desktop computer  54 B, laptop computer  54 C, and/or automobile computer system  54 N may communicate. Nodes  50  may communicate with one another. They may be grouped (not shown) physically or virtually, in one or more networks, such as Private, Community, Public, or Hybrid clouds as described hereinabove, or a combination thereof. This allows cloud computing environment  52  to offer infrastructure, platforms and/or software as services for which a cloud consumer does not need to maintain resources on a local computing device. It is understood that the types of computing devices  54 A-N shown in  FIG.  1 B  are intended to be illustrative only and that computing nodes  50  and cloud computing environment  52  can communicate with any type of computerized device over any type of network and/or network addressable connection (e.g., using a web browser). 
     Referring now to  FIG.  1 C , a set of functional abstraction layers provided by cloud computing environment  52  ( FIG.  1 B ) is shown. It should be understood in advance that the components, layers, and functions shown in  FIG.  1 C  are intended to be illustrative only and embodiments of the invention are not limited thereto. As depicted, the following layers and corresponding functions are provided: 
     Hardware and software layer  60  includes hardware and software components. Examples of hardware components include: mainframes  61 ; RISC (Reduced Instruction Set Computer) architecture based servers  62 ; servers  63 ; blade servers  64 ; storage devices  65 ; and networks and networking components  66 . In some embodiments, software components include network application server software  67  and database software  68 . 
     Virtualization layer  70  provides an abstraction layer from which the following examples of virtual entities may be provided: virtual servers  71 ; virtual storage  72 ; virtual networks  73 , including virtual private networks; virtual applications and operating systems  74 ; and virtual clients  75 . 
     In one example, management layer  80  may provide the functions described below. Resource provisioning  81  provides dynamic procurement of computing resources and other resources that are utilized to perform tasks within the cloud computing environment. Metering and Pricing  82  provide cost tracking as resources are utilized within the cloud computing environment, and billing or invoicing for consumption of these resources. In one example, these resources may include application software licenses. Security provides identity verification for cloud consumers and tasks, as well as protection for data and other resources. User portal  83  provides access to the cloud computing environment for consumers and system administrators. Service level management  84  provides cloud computing resource allocation and management such that required service levels are met. Service Level Agreement (SLA) planning and fulfillment  85  provide pre-arrangement for, and procurement of, cloud computing resources for which a future requirement is anticipated in accordance with an SLA. 
     Workloads layer  90  provides examples of functionality for which the cloud computing environment may be utilized. Examples of workloads and functions which may be provided from this layer include: mapping and navigation  91 ; software development and lifecycle management  92 ; virtual classroom education delivery  93 ; data analytics processing  94 ; transaction processing  95 ; and mobile desktop  96 . 
     Any of the nodes  50  in the computing environment  52  as well as the computing devices  54 A-N may be a DPS  10 . 
     Blockchain Basic Detail 
     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 example 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 provide for a privacy-preserving attribute-based document sharing in blockchain networks. 
     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. 
     Some benefits of the instant solutions described and depicted herein include a method and system for a privacy-preserving attribute-based document sharing in blockchain networks in blockchain networks. The example embodiments solve the issues of time and trust by extending features of a database such as immutability, digital signatures and being a single source of truth. The example embodiments provide a solution for a privacy-preserving attribute-based document sharing in blockchain networks in blockchain-based network. The blockchain networks may be homogenous based on the asset type and rules that govern the assets based on the smart contracts. 
     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, which are further described herein. According to various aspects, the system for a privacy-preserving attribute-based document sharing in blockchain networks in blockchain networks is implemented due to immutable accountability, security, privacy, permitted decentralization, availability of smart contracts, endorsements and accessibility that are inherent and unique to blockchain. In particular, the blockchain ledger data is immutable and that provides for efficient method for a privacy-preserving attribute-based document sharing in blockchain networks in blockchain networks. Also, use of the encryption in the blockchain provides security and builds trust. The smart contract manages the state of the asset to complete the life-cycle. The example blockchains are permission decentralized. Thus, each end user may have its own ledger copy to access. Multiple organizations (and peers) may be on-boarded on the blockchain network. The key organizations may serve as endorsing peers to validate the smart contract execution results, read-set and write-set. In other words, the blockchain inherent features provide for efficient implementation of a method for a privacy-preserving attribute-based document sharing in blockchain networks. 
     One of the benefits of the example embodiments is that it improves the functionality of a computing system by implementing a method for a privacy-preserving attribute-based document sharing in blockchain-based systems. Through the blockchain system described herein, a computing system can perform functionality for a privacy-preserving attribute-based document sharing in blockchain networks in blockchain networks by providing access to capabilities such as distributed ledger, peers, encryption technologies, MSP, event handling, etc. Also, the blockchain enables to create a business network and make any users or organizations to on-board for participation. As such, the blockchain is not just a database. The blockchain comes with capabilities to create a Business Network of users and on-board/off-board organizations to collaborate and execute service processes in the form of smart contracts. 
     The example embodiments provide numerous benefits over a traditional database. For example, through the blockchain the embodiments provide for immutable accountability, security, privacy, permitted decentralization, availability of smart contracts, endorsements and accessibility that are inherent and unique to the blockchain. 
     Meanwhile, a traditional database could not be used to implement the example embodiments because it does not bring all parties on the business network, it does not create trusted collaboration and does not provide for an efficient storage of digital assets. The traditional database does not provide for a tamper proof storage and does not provide for preservation of the digital assets being stored. Thus, the proposed method for a privacy-preserving attribute-based document sharing in blockchain networks cannot be implemented in the traditional database. 
     Meanwhile, if a traditional database were to be used to implement the example embodiments, the example embodiments would have suffered from unnecessary drawbacks such as search capability, lack of security and slow speed of transactions. Additionally, the automated method for a privacy-preserving attribute-based document sharing in a blockchain network would simply not be possible. 
     Accordingly, the example embodiments provide for a specific solution to a problem in the arts/field of an attribute-based document sharing. 
     The example embodiments also change how data may be stored within a block structure of the blockchain. For example, a digital asset data may be securely stored within a certain portion of the data block (i.e., within header, data segment, or metadata). By storing the digital asset data within data blocks of a blockchain, the digital asset data may be appended to an immutable blockchain ledger through a hash-linked chain of blocks. In some embodiments, the data block may be different than a traditional data block by having a personal data associated with the digital asset not stored together with the assets within a traditional block structure of a blockchain. By removing the personal data associated with the digital asset, the blockchain can provide the benefit of anonymity based on immutable accountability and security. 
     According to the example embodiments, a system and method for a privacy-preserving attribute-based document sharing in blockchain networks are provided. A blockchain document processor may have two components:
         a private off-chain processor that manages secure processing of private information related to a participant; and   a ledger processor that manages processing of common information shared with all participants of a blockchain network using the consensus algorithm of the network.       

     According to the example embodiments, each of the organizations that intend to share documents with other organizations uses a blockchain document processor connected to a blockchain network. Using the document processor, the organizations may set up the following on the ledger:
         a list of document templates;   attributes of each document template that will be shared in hashed form on the ledger;   a combination of key attributes from different templates for matching and sharing documents; and   partnership Merkel trees: each partnership Merkel tree may be built based on partnering organizations&#39; identifiers (IDs).       

     All documents (files, JSONs) are stored on the off-chain data store. Only the attribute hashes and the document identifier (ID) are submitted as a part of a blockchain transaction. 
     According to one example embodiment, a document identifier and a document type may be linked to hashed attributes for sharing. Hashed owner&#39;s organization id may include composite keys such that:
         given the document ID, a document processor may get all hashed attributes for sharing; and   given a hashed attribute for sharing, the document processor may get all document IDs and their hashed owner organization id.       

     When a document is recorded and given its hashed attributes for sharing, the document processor may get all the documents and their hashed owner organization IDs. The processor may check if incoming document owner organization ID and each owner organization IDs are part of a partnership Merkel tree. If the IDs belong to the partnership Merkel tree for the subset of documents within an eligible organization relationship, the processor may get the required templates for logic matching. Based on evaluating the hashed attribute matching, the processor may get the list of documents (and their owners) to which the incoming document needs to be linked. Then, the processor may create the linked documents. The processor may generate a one-time pass code so that the participants can link to this document and pass it through all participants. The participants may then query the blockchain with the one-time pass code and hashed organization ID to retrieve the incoming document key. Using the document key, the participant may retrieve the shared document from the owning party (i.e., a blockchain node) and store the document on the recipient&#39;s off-chain storage. 
       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 document attribute(s) information  226  may be processed by one or more processing entities (e.g., virtual machines) included in the blockchain layer  216 . The result  228  may include a plurality of linked shared documents. 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 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. 
       FIG.  2 B  illustrates an example of a blockchain transactional flow  250  between nodes of the blockchain in accordance with an example embodiment. Referring to  FIG.  2 B , the transaction flow may include a transaction proposal  291  sent by an application client node  260  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). The proposal response  292  is sent back to the client  260  along with an endorsement signature, if approved. The client  260  assembles the endorsements into a transaction payload  293  and broadcasts it to an ordering service node  284 . The ordering service node  284  then delivers ordered transactions as blocks to all peers  281 - 283  on a channel. Before committal to the blockchain, each peer  281 - 283  may validate the transaction. For example, the peers may check the endorsement policy to ensure that the correct allotment of the specified peers have signed the results and authenticated the signatures against the transaction payload  293 . 
     Referring again to  FIG.  2 B , the client node  260  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 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 of the transaction are delivered from the ordering node  284  to all peer nodes  281 - 283  on the channel. The transactions  294  within the block are validated to ensure any 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. Transactions in the block are tagged as being valid or invalid. 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 is 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    is a block diagram that illustrates a basic blockchain sequence  400  of three transactions. The first block contains a first header  410   a  and a first group of transactions  420   a  making up the first block. The block header contains a hash  412   a  of the previous block header and a Merkle root  414   a . The Merkle root  414   a  is a hash of all the hashes of all the transactions that are part of a block in a blockchain network that ensures data blocks passed between peers are whole, undamaged, and unaltered. The second block contains a second header  410   b  and a second group of transactions  420   b  making up the second block. The block header contains a hash  412   b  of the previous block header  410   a  and a Merkle root  414   b . The third block contains a third header  410   c  and a third group of transactions  420   c  making up the third block. The block header contains a hash  412   c  of the previous block header  410   b  and a Merkle root  414   c . The number of blocks may be extended to any feasible length and hash values may be checked/verified with relative ease. 
       FIG.  5 A  illustrates an example system  500  that includes a physical infrastructure  510  configured to perform various operations according to example embodiments. Referring to  FIG.  5 A , the physical infrastructure  510  includes a module  512  and a module  514 . The module  514  includes a blockchain  520  and a smart contract  530  (which may reside on the blockchain  520 ), that may execute any of the operational steps  508  (in module  512 ) included in any of the example embodiments. The steps/operations  508  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  530  and/or blockchains  520 . The physical infrastructure  510 , the module  512 , and the module  514  may include one or more computers, servers, processors, memories, and/or wireless communication devices. Further, the module  512  and the module  514  may be a same module. 
       FIG.  5 B  illustrates another example system  540  configured to perform various operations according to example embodiments. Referring to  FIG.  5 B , the system  540  includes a module  512  and a module  514 . The module  514  includes a blockchain  520  and a smart contract  530  (which may reside on the blockchain  520 ), that may execute any of the operational steps  508  (in module  512 ) included in any of the example embodiments. The steps/operations  508  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  530  and/or blockchains  520 . The physical module  512  and the module  514  may include one or more computers, servers, processors, memories, and/or wireless communication devices. Further, the module  512  and the module  514  may be a same module. 
       FIG.  5 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.  5 C , the configuration  550  may represent a communication session, an asset transfer session or a process or procedure that is driven by a smart contract  530  which explicitly identifies one or more user devices  552  and/or  556 . The execution, operations and results of the smart contract execution may be managed by a server  554 . Content of the smart contract  530  may require digital signatures by one or more of the entities  552  and  556  which are parties to the smart contract transaction. The results of the smart contract execution may be written to a blockchain  520  as a blockchain transaction. The smart contract  530  resides on the blockchain  520  which may reside on one or more computers, servers, processors, memories, and/or wireless communication devices. 
       FIG.  5 D  illustrates a system  560  including a blockchain, according to example embodiments. Referring to the example of  FIG.  5 D , an application programming interface (API) gateway  562  provides a common interface for accessing blockchain logic (e.g., smart contract  530  or other chaincode) and data (e.g., distributed ledger, etc.). In this example, the API gateway  562  is a common interface for performing transactions (invoke, queries, etc.) on the blockchain by connecting one or more entities  552  and  556  to a blockchain peer (i.e., server  554 ). Here, the server  554  is a blockchain network peer component that holds a copy of the world state and a distributed ledger allowing clients  552  and  556  to query data on the world state as well as submit transactions into the blockchain network where, depending on the smart contract  530  and endorsement policy, endorsing peers will run the smart contracts  530 . 
     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 example 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.  6 A  illustrates a process  600  of a new block being added to a distributed ledger  620 , according to example embodiments, and  FIG.  6 B  illustrates contents of a new data block structure  630  for blockchain, according to example embodiments. The new data block  630  may contain document linking data. 
     Referring to  FIG.  6 A , clients (not shown) may submit transactions to blockchain nodes  611 ,  612 , and/or  613 . Clients may be instructions received from any source to enact activity on the blockchain  620 . 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  611 ,  612 , and  613 ) may maintain a state of the blockchain network and a copy of the distributed ledger  620 . 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  620 . In this example, the blockchain nodes  611 ,  612 , and  613  may perform the role of endorser node, committer node, or both. 
     The distributed ledger  620  includes a blockchain which stores immutable, sequenced records in blocks, and a state database  624  (current world state) maintaining a current state of the blockchain  622 . One distributed ledger  620  may exist per channel and each peer maintains its own copy of the distributed ledger  620  for each channel of which they are a member. The blockchain  622  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.  6 B . The linking of the blocks (shown by arrows in  FIG.  6 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  622  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  622  represents every transaction that has come before it. The blockchain  622  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  622  and the distributed ledger  622  may be stored in the state database  624 . Here, the current state data represents the latest values for all keys ever included in the chain transaction log of the blockchain  622 . Chaincode invocations execute transactions against the current state in the state database  624 . To make these chaincode interactions extremely efficient, the latest values of all keys are stored in the state database  624 . The state database  624  may include an indexed view into the transaction log of the blockchain  622 , it can therefore be regenerated from the chain at any time. The state database  624  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 node 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  610 . 
     The ordering service  610  accepts endorsed transactions, orders them into a block, and delivers the blocks to the committing peers. For example, the ordering service  610  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.  6 A , blockchain node  612  is a committing peer that has received a new data new data block  630  for storage on blockchain  620 . 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  610  may be made up of a cluster of orderers. The ordering service  610  does not process transactions, smart contracts, or maintain the shared ledger. Rather, the ordering service  610  may accept the endorsed transactions and specifies the order in which those transactions are committed to the distributed ledger  620 . 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  620  in a consistent order. The order of transactions is established to ensure that the updates to the state database  624  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  620  may choose the ordering mechanism that best suits that network. 
     When the ordering service  610  initializes a new data block  630 , the new data block  630  may be broadcast to committing peers (e.g., blockchain nodes  611 ,  612 , and  613 ). In response, each committing peer validates the transaction within the new data block  630  by checking to make sure that the read set and the write set still match the current world state in the state database  624 . 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  624 . When the committing peer validates the transaction, the transaction is written to the blockchain  622  on the distributed ledger  620 , and the state database  624  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  624 , the transaction ordered into a block will still be included in that block, but it will be marked as invalid, and the state database  624  will not be updated. 
     Referring to  FIG.  6 B , a new data block  630  (also referred to as a data block) that is stored on the blockchain  622  of the distributed ledger  620  may include multiple data segments such as a block header  640 , block data  650 , and block metadata  660 . It should be appreciated that the various depicted blocks and their contents, such as new data block  630  and its contents. Shown in  FIG.  6 B  are merely examples and are not meant to limit the scope of the example embodiments. The new data block  630  may store transactional information of N transaction(s) (e.g., 1, 10, 100, 500, 1000, 2000, 3000, etc.) within the block data  650 . The new data block  630  may also include a link to a previous block (e.g., on the blockchain  622  in  FIG.  6 A ) within the block header  640 . In particular, the block header  640  may include a hash of a previous block&#39;s header. The block header  640  may also include a unique block number, a hash of the block data  650  of the new data block  630 , and the like. The block number of the new data block  630  may be unique and assigned in various orders, such as an incremental/sequential order starting from zero. 
     The block data  650  may store transactional information of each transaction that is recorded within the new data block  630 . For example, the transaction data may include one or more of a type of the transaction, a version, a timestamp, a channel ID of the distributed ledger  620 , a transaction ID, an epoch, a payload visibility, a chaincode path (deploy tx), a chaincode name, a chaincode version, input (chaincode and functions), a client (creator) identify such as a public key and certificate, a signature of the client, identities of endorsers, endorser signatures, a proposal hash, chaincode events, response status, namespace, a read set (list of key and version read by the transaction, etc.), a write set (list of key and value, etc.), a start key, an end key, a list of keys, a Merkel tree query summary, and the like. The transaction data may be stored for each of the N transactions. 
     In some embodiments, the block data  650  may also store new data  662  which adds additional information to the hash-linked chain of blocks in the blockchain  622 . The additional information includes one or more of the steps, features, processes and/or actions described or depicted herein. Accordingly, the new data  662  can be stored in an immutable log of blocks on the distributed ledger  620 . Some of the benefits of storing such new data  662  are reflected in the various embodiments disclosed and depicted herein. Although in  FIG.  6 B  the new data  662  is depicted in the block data  650  but could also be located in the block header  640  or the block metadata  660 . The new data  662  may include a document composite key that is used for linking the documents within an organization. 
     The block metadata  660  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  610 . Meanwhile, a committer of the block (such as blockchain node  612 ) 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 in the block data  650  and a validation code identifying whether a transaction was valid/invalid. 
       FIG.  6 C  illustrates an embodiment of a blockchain  670  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 in to 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.  6 C , the blockchain  670  includes a number of blocks  678   1 ,  678   2 , . . .  678   N  cryptographically linked in an ordered sequence, where N≥1. The encryption used to link the blocks  678   1 ,  678   2 , . . .  678   N  may be any of a number of keyed or un-keyed Hash functions. In one embodiment, the blocks  678   1 ,  678   2 , . . .  678   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  678   1 ,  678   2 , . . . ,  678   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  678   1 ,  678   2 , . . . ,  678   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  678   1  in the blockchain is referred to as the genesis block and includes the header  672   1 , original file  674   1 , and an initial value  676   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  678   1  may be hashed together and at one time, or each or a portion of the information in the first block  678   1  may be separately hashed and then a hash of the separately hashed portions may be performed. 
     The header  672   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  674   1  and/or the blockchain. The header  672   1  may be generated automatically (e.g., by blockchain network managing software) or manually by a blockchain participant. Unlike the header in other blocks  678   2  to  678   N  in the blockchain, the header  672   1  in the genesis block does not reference a previous block, simply because there is no previous block. 
     The original file  674   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  674   1  is received through the interface of the system from the device, media source, or node. The original file  674   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  678   1  in association with the original file  674   1 . 
     The value  676   1  in the genesis block is an initial value generated based on one or more unique attributes of the original file  674   1 . In one embodiment, the one or more unique attributes may include the hash value for the original file  674   1 , metadata for the original file  674   1 , and other information associated with the file. In one implementation, the initial value  676   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  678   2  to  678   N  in the blockchain also have headers, files, and values. However, unlike the first block  672   1 , each of the headers  672   2  to  672   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  680 , to establish an auditable and immutable chain-of-custody. 
     Each of the header  672   2  to  672   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  674   2  to  674   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  676   2  to  676   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.  6 D  illustrates an embodiment of a block which may represent the structure of the blocks in the blockchain  690  in accordance with one embodiment. The block, Blocki, includes a header  672   i , a file  674   i , and a value  676   i.    
     The header  672   i  includes a hash value of a previous block Blocki−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  674   i  includes a plurality of data, such as Data  1 , Data  2 , . . . , Data N in sequence. The data are tagged with Metadata  1 , Metadata  2 , . . . , Metadata N which describe the content and/or characteristics associated with the data. For example, the metadata for each data may include information to indicate a timestamp for the data, process the data, keywords indicating the persons or other content depicted in the data, and/or other features that may be helpful to establish the validity and content of the file as a whole, and particularly its use a digital evidence, for example, as described in connection with an embodiment discussed below. In addition to the metadata, each data may be tagged with reference REF 1 , REF 2 , . . . , REFN 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  676   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 Blocki, 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  670  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 (Nth) 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.  7 A and  7 B  illustrate additional examples of use cases for blockchain which may be incorporated and used herein. In particular,  FIG.  7 A  illustrates an example  700  of a blockchain  710  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.  7 A , a host platform  720  builds and deploys a machine learning model for predictive monitoring of assets  730 . Here, the host platform  720  may be a cloud platform, an industrial server, a web server, a personal computer, a user device, and the like. Assets  730  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  730  may be non-tangible assets such as stocks, currency, digital coins, insurance, or the like. 
     The blockchain  710  can be used to significantly improve both a training process  702  of the machine learning model and a predictive process  704  based on a trained machine learning model. For example, in  702 , rather than requiring a data scientist/engineer or other user to collect the data, historical data may be stored by the assets  730  themselves (or through an intermediary, not shown) on the blockchain  710 . This can significantly reduce the collection time needed by the host platform  720  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  710 . By using the blockchain  710  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  730 . 
     The collected data may be stored in the blockchain  710  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  720 . 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  702 , the different training and testing steps (and the data associated therewith) may be stored on the blockchain  710  by the host platform  720 . Each refinement of the machine learning model (e.g., changes in variables, weights, etc.) may be stored on the blockchain  710 . This provides verifiable proof of how the model was trained and what data was used to train the model. Furthermore, when the host platform  720  has achieved a finally trained model, the resulting model may be stored on the blockchain  710 . 
     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  704 , 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  730  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  720  may be stored on the blockchain  710  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  730  and create alert or a notification to replace the part. The data behind this decision may be stored by the host platform  720  on the blockchain  710 . In one embodiment the features and/or the actions described and/or depicted herein can occur on or with respect to the blockchain  710 . 
     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.  7 B  illustrates an example  750  of a quantum-secured blockchain  752  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.  7 B , four users are present  754 ,  756 ,  758 , and  760 . Each of pair of users may share a secret key  762  (i.e., a QKD) between themselves. Since there are four nodes in this example, six pairs of nodes exist, and therefore six different secret keys  762  are used including QKDAB, QKDAC, QKDAD, QKDBC, QKDBD, and QKDCD. 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  752  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  754 - 760 ) authenticate the transaction by providing their shared secret key  762  (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  752  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  752 . In one embodiment the features and/or the actions described and/or depicted herein can occur on or with respect to the blockchain  752 . 
     Referring now to  FIG.  8   , shown is a high-level block diagram of an example computer system  800  that may be used in implementing one or more of the methods, tools, and modules, and any related functions, described herein (e.g., using one or more processor circuits or computer processors of the computer), in accordance with embodiments of the present disclosure. This computer system may, in some embodiments, be a DPS  10  as described above. In some embodiments, the major components of the computer system  800  may comprise one or more CPUs  802 , a memory subsystem  804 , a terminal interface  812 , a storage interface  816 , an I/O (Input/Output) device interface  814 , and a network interface  818 , all of which may be communicatively coupled, directly or indirectly, for inter-component communication via a memory bus  803 , an I/O bus  808 , and an I/O bus interface unit  810 . 
     The computer system  800  may contain one or more general-purpose programmable central processing units (CPUs)  802 A,  802 B,  802 C, and  802 D, herein generically referred to as the CPU  802 . In some embodiments, the computer system  800  may contain multiple processors typical of a relatively large system; however, in other embodiments the computer system  800  may alternatively be a single CPU system. Each CPU  802  may execute instructions stored in the memory subsystem  804  and may include one or more levels of on-board cache. 
     System memory  804  may include computer system readable media in the form of volatile memory, such as random access memory (RAM)  822  or cache memory  824 . Computer system  800  may further include other removable/non-removable, volatile/non-volatile computer system storage media. By way of example only, storage system  826  can be provided for reading from and writing to a non-removable, non-volatile magnetic media, such as 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”), or an optical disk drive for reading from or writing to a removable, non-volatile optical disc such as a CD-ROM, DVD-ROM or other optical media can be provided. In addition, memory  804  can include flash memory, e.g., a flash memory stick drive or a flash drive. Memory devices can be connected to memory bus  803  by one or more data media interfaces. The memory  804  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. 
     One or more programs/utilities  828 , each having at least one set of program modules  830  may be stored in memory  804 . The programs/utilities  828  may include a hypervisor (also referred to as a virtual machine monitor), one or more operating systems, one or more application programs, other program modules, and program data. Each of the operating systems, one or more application programs, other program modules, and program data or some combination thereof, may include an implementation of a networking environment. Programs  828  and/or program modules  830  generally perform the functions or methodologies of various embodiments. 
     Although the memory bus  803  is shown in  FIG.  8    as a single bus structure providing a direct communication path among the CPUs  802 , the memory subsystem  804 , and the I/O bus interface  810 , the memory bus  803  may, in some embodiments, include multiple different buses or communication paths, which may be arranged in any of various forms, such as point-to-point links in hierarchical, star or web configurations, multiple hierarchical buses, parallel and redundant paths, or any other appropriate type of configuration. Furthermore, while the I/O bus interface  810  and the I/O bus  808  are shown as single respective units, the computer system  800  may, in some embodiments, contain multiple I/O bus interface units  810 , multiple I/O buses  808 , or both. Further, while multiple I/O interface units are shown, which separate the I/O bus  808  from various communications paths running to the various I/O devices, in other embodiments some or all of the I/O devices may be connected directly to one or more system I/O buses. 
     In some embodiments, the computer system  800  may be a multi-user mainframe computer system, a single-user system, or a server computer or similar device that has little or no direct user interface, but receives requests from other computer systems (clients). Further, in some embodiments, the computer system  800  may be implemented as a desktop computer, portable computer, laptop or notebook computer, tablet computer, pocket computer, telephone, smartphone, network switches or routers, or any other appropriate type of electronic device. 
       FIG.  8    depicts the representative major components of an example computer system  800 . In some embodiments, however, individual components may have greater or lesser complexity than as represented in  FIG.  8   , components other than or in addition to those shown in  FIG.  8    may be present, and the number, type, and configuration of such components may vary. 
     As discussed in more detail herein, it is contemplated that some or all of the operations of some of the embodiments of methods described herein may be performed in alternative orders or may not be performed at all; furthermore, multiple operations may occur at the same time or as an internal part of a larger process. 
     Blockchain Endorsement Agreement 
     Building a useful smart contract utilizes multiple inputs to prove contractual performance, as well as multiple outputs to affect outside systems and/or send payment to complete the smart contract. Smart contracts require secure middleware to connect them to external real-world data. This external data triggers the contract, creating the need for its high reliability. However, smart contracts cannot access data on their own. When developers implement a particular smart contract, they encounter a connectivity problem. The smart contract may be unable to connect with key external resources, like off-chain data and application program interfaces (APIs). This lack of external connectivity is due to the method by which consensus is reached around a blockchain&#39;s transaction data, and is a problem for every smart contract network. 
     Disclosed herein is a novel system employed with of two pieces of functionality: the first piece of functionality is executed by an endorser peer, and the second piece of functionality is implemented once results from the other endorser peers are obtained. This second piece of functionality calculates the final result and determines if there is an agreed result among the endorser peers. If so, it endorses the agreed result prior to sending it to the client. 
     As illustrated in  FIG.  9 A , which is a block diagram of a smart contract system  900  with a single connection node  910 , connecting smart contracts  915  to data inputs  905  through a single node  910  creates the same problem that smart contracts  915  themselves seek to avoid—a single point of failure, shown as the failed node  910 . With a single oracle node  910 , the smart contract is only as reliable as that one node  910 , and if it fails, the smart contracts  915  are not able to execute. 
       FIG.  9 B  is a block diagram of a smart contract system  900 ′ that provides a more reliable and tamper-proof mechanism for complex smart contracts on a blockchain. Here, a plurality of data inputs  905 A,  905 B,  905 C communicate through respective nodes  910 A,  910 B,  910 C of the network to implement the smart contracts  915  in a more robust manner. The decentralized Oracle network provides the same security guarantees as smart contracts themselves. By allowing multiple entities to evaluate the same data before it becomes a trigger, any one point of failure is eliminated, and the overall value of a smart contract that is highly secure, reliable, and trustworthy is maintained. 
       FIGS.  10 A and  10 B  are a block diagrams illustrating the use of endorser peers with a trained model or service.  FIG.  10 A  shows the blockchain client  1005  that interacts with a plurality of endorser peers  1010 A,  1010 B,  1010 C, (representatively or collectively  1010 ) each accessing a respective trained model or service  1015 A,  1015 B,  1015 C (representatively or collectively  1015 ) to assist in determining PERs and agreements. Model provisioning for the endorser peers  1010  may be done at development time or dynamically configured at each endorser peer  1010 . Each endorser peer  1010  may use different versions of a model  1015 , or the same models  1015 , but trained with different training datasets, or they may use completely different trained models  1015 . Trained models  1015  do not need to be stored into the blockchain network as they may be provisioned to endorser peers  1010  as part of a continuous integration (CI) workflow, such as, e.g., KubeFlow®. 
     A client application  1007  on the blockchain client  1005  may submit a transaction request or proposal  1011  in a normal manner to a plurality of endorser piers  1010 . The client application  1007  may also receive endorsement results  1030  from the endorser peers  1010  in the normal manner. However, endorsements  1030  may have been obtained by executing agreement logic  1070 , which may form a part of the smart contract  1060 , on shared pre-endorsement results (PERs)  1013 . In other words, the smart contract  1060  ( FIG.  10 B ) contains logic for managing asset assignments and agreement logic  1070  to determine an agreement based on peers&#39;  1010  PERs  1013 . 
       FIG.  10 B  illustrates the flow of the transaction proposal  1011  sent from the blockchain client  1005  to each of the endorser peers  1010 A,  1010 B,  1010 C, that each respectively compute local PERs  1020 A,  1020 B,  1020 C for the transaction proposal (TP)  1011  which are shared  1013  among the endorser peers  1010 . The transaction proposal  1011  created by the blockchain client  1005  may include the list of endorser peers  1010  in order for the endorser peers  1010  to communicate and exchange PERs  1013 . 
     The smart contract  1060  agreement logic  1070  may, in some embodiments, be a set of statements executed by each endorser peer  1010  once the PERs  1013  are collected from other endorser peers  1010 . The endorser peers  1010  compute from the shared PERs  1013 , whether agreement among the endorser peers  1010  exists, and the respective computed agreements  1025 A,  1025 B,  1025 C from each of the endorser peers  1010 A,  1010 B,  1010 C, is returned to the blockchain client  1005 . During the endorsement agreement phase, the endorser peers  1010  are provisioned with trained models/services  1015  or some other mechanism that allows the endorser peers  1010  to propose pre-endorsement results, and the agreement logic  1070  allows for the determination of a final endorsement result. If one of the peers  1010  reports no agreement, the endorsing policy ultimately determines of the output is finally committed as a valid transaction. 
     If all goes as planned, the endorser peers finally endorse an agreed result  1030  received by the blockchain client  1005 . When enough endorser peers  1005  agree on the final endorsed result  1030  (according to the terms of the endorsing policy  1065  of the smart contract  1060 ) the client  1005  submits the endorsed transaction  1035  for block generation  1040 , and the endorsed transaction  1035  is committed and the assignment of the transaction record to the blockchain is completed. 
     In this way, endorser peers  1010  may be provisioned with behavior via, e.g., trained models or services  1015 , and a final endorsement by the endorser peers  1010  depends not only on the local computations but also on the results obtained by the endorser peers  1010  executing the same transaction submitted by the blockchain client  1005 . The smart contract  1060  implements the expected behavior and logic to calculate the final result based on the local calculated results before sending the endorsed result to the blockchain client  1005  who originally submitted the transaction proposal or request  1011 . 
     The following use case provides, by way of example, an application of the agreement logic described above. In the use case, port containers are used in the transport industry to move products from a source location to a destination location. Port containers are often of a standardized size and are secured containers that may contain products from a wide variety of ultimate source locations intended for a wide variety of destination locations. However, the port container holding the products generally has a specific single source location and a single intended destination location for the particular leg of the journey (e.g., an overseas transport on a ship) that is applied to the port container. 
     The port container may be brought to the source location for the overseas transport by, e.g., a preliminary transport such as a truck in a leg of the journey prior to the overseas journey. However, there may be several possibilities for the source location, as there may be any number of ports from which the port container may be shipped from. The use of a smart contract may help in determining the source location. The smart contract  1060  may be used for location management based on available or assigned potential locations. The agreement logic  1070  may be used to obtain the optimal assignments based on multiple pre-endorsements  1030 . In this example, each endorser peer  1010  may generate a list of preferred source locations for the source location assignment. Such a list may be provided by the business logic data required as input for the smart contract. The specific data may be determined by an application (the smart contract being a component of an overall solution. The agreement logic  1070  may specify that each endorser peer  1010  may choose the optimal result based on provided preference lists. The agreement logic  1070  may also specify that the endorser peer  1010  should make an effort to prevent a “no agreement” state from arising—for example, the agreement logic  1070  may specify that if no result can be found amongst the endorser peers  1010 , then the endorser peers  1010  should us a first free source location, based on the location ID asc. 
     In some implementations, deterministic logic may be preferred in the agreement logic  1070  for the agreement to succeed, i.e., all endorser peers  1010  arrive at the same endorsed result. In the case in which the PERs differ (and thus, no result may be obtained from preferred lists) each endorser peer  1010  may provide, as a final result, the first free source location. The endorser peers should agree on the first free source location, unless one or more is compromised—but in any, an adequate number of them should. In the case in which the PERs agree, i.e., they all provide an optimal location, e.g., all of the endorser peers  1010  set the same source location as the best source location, and then, each endorser peer  1010  will endorse this source location. Thus, this novel system may be utilized, in this example, by assigning a physical asset location in a de-centralized manner backed by blockchain and multiple trained models. 
       FIG.  11    is a flowchart of a process  1100  that may be executed by an endorser peer  1010 . In operation  1105 , the endorser peer  1010  receives a transaction proposal  1011  from a blockchain client  1005 . In operation  1110 , the endorser peer  1010  determines a PER  1020  associated with the transaction proposal  1011 . In operation  1112 , the endorser peer  1010  receives PERs  1020  from other endorser peers  1010 . In operation  1115 , the endorser peer  1010  analyzes the PERs and produces an agreed result  1025 . In operation  1120 , the endorser peer  1010  endorses the agreed result, and in operation  1125 , the endorser peer  1010  sends the endorsed agreed result to the blockchain client  1005 . 
     Technical Application 
     The one or more embodiments disclosed herein accordingly provide an improvement to computer technology. For example, an improvement to a digital transaction ledger allows for more, efficient, and effective computer transaction implementation when using smart contracts. 
     Computer Readable Media 
     The present invention may be a system, a method, and/or a computer readable media at any possible technical detail level of integration. The computer program product may include a computer readable storage medium (or media) having computer readable program instructions thereon for causing a processor to carry out aspects of the present invention. 
     The computer readable storage medium can be a tangible device that can retain and store instructions for use by an instruction execution device. The computer readable storage medium may be, for example, but is not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. A non-exhaustive list of more specific examples of the computer readable storage medium includes the following: a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanically encoded device such as punch-cards or raised structures in a groove having instructions recorded thereon, and any suitable combination of the foregoing. A computer readable storage medium, as used herein, is not to be construed as being transitory signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission media (e.g., light pulses passing through a fiber-optic cable), or electrical signals transmitted through a wire. 
     Computer readable program instructions described herein can be downloaded to respective computing/processing devices from a computer readable storage medium or to an external computer or external storage device via a network, for example, the Internet, a local area network, a wide area network and/or a wireless network. The network may comprise copper transmission cables, optical transmission fibers, wireless transmission, routers, firewalls, switches, gateway computers and/or edge servers. A network adapter card or network interface in each computing/processing device receives computer readable program instructions from the network and forwards the computer readable program instructions for storage in a computer readable storage medium within the respective computing/processing device. 
     Computer readable program instructions for carrying out operations of the present invention may be assembler instructions, instruction-set-architecture (ISA) instructions, machine instructions, machine dependent instructions, microcode, firmware instructions, state-setting data, configuration data for integrated circuitry, or either source code or object code written in any combination of one or more programming languages, including an object oriented programming language such as Smalltalk, C++, or the like, and procedural programming languages, such as the “C” programming language or similar programming languages. The computer readable program instructions may execute entirely on the user&#39;s computer, partly on the user&#39;s computer, as a stand-alone software package, partly on the user&#39;s computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user&#39;s computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider). In some embodiments, electronic circuitry including, for example, programmable logic circuitry, field-programmable gate arrays (FPGA), or programmable logic arrays (PLA) may execute the computer readable program instructions by utilizing state information of the computer readable program instructions to personalize the electronic circuitry, in order to perform aspects of the present invention. 
     Aspects of the present invention are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer readable program instructions. 
     These computer readable program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. These computer readable program instructions may also be stored in a computer readable storage medium that can direct a computer, a programmable data processing apparatus, and/or other devices to function in a particular manner, such that the computer readable storage medium having instructions stored therein comprises an article of manufacture including instructions which implement aspects of the function/act specified in the flowchart and/or block diagram block or blocks. 
     The computer readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable apparatus or other device to produce a computer implemented process, such that the instructions which execute on the computer, other programmable apparatus, or other device implement the functions/acts specified in the flowchart and/or block diagram block or blocks. 
     The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of instructions, which comprises one or more executable instructions for implementing the specified logical function(s). In some alternative implementations, the functions noted in the blocks may occur out of the order noted in the Figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts or carry out combinations of special purpose hardware and computer instructions.