Patent Publication Number: US-11379866-B2

Title: Retrieving values of digital tickets using smart contracts in blockchain networks

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of and claims the benefit of priority of U.S. patent application Ser. No. 16/671,032, filed Oct. 31, 2019, which is a continuation of PCT Application No. PCT/CN2019/082541, filed on Apr. 12, 2019, which is hereby incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     This specification relates to retrieving values of digital tickets using smart contracts in blockchain networks. 
     BACKGROUND 
     Distributed ledger systems (DLSs), which can also be referred to as consensus networks, and/or blockchain networks, enable participating entities to securely, and immutably store data. DLSs are commonly referred to as blockchain networks without referencing any particular user case. Examples of types of blockchain networks can include public blockchain networks, private blockchain networks, and consortium blockchain networks. A consortium blockchain network is provided for a select group of entities, which control the consensus process, and includes an access control layer. 
     The blockchain networks can be used for implementing electronic trading systems or platforms. The electronic trading systems may distribute electronic coupons to consumers for promotional purposes. The electronic coupons have penetrated into all aspects of merchant products and services and can be redeemed by consumers for purchasing products or services on an electronic trading platform. Examples of the electronic coupons (or promotional coupons) include discount coupons which can be used by consumers at the time of consumption to purchase a product at a discounted price according to a discount rate indicated by the discount coupons, and electronic vouchers that have certain monetary values and can be exchanged for goods and services. 
     In some instances, the electronic coupons are associated with a value (e.g., a discount rate of a discount coupon, or a monetary value of an electronic voucher) that can be redeemed at a specific time point or within a short time window. As a result, consumers tend to redeem the electronic coupons at a same time or within a short time window, thereby increasing pressure on the computer systems that process the requests from the consumers to redeem the electronic coupons. Furthermore, information stored in the electronic coupons (e.g., a discount rate of a discount coupon, or a monetary value of an electronic voucher) may be tampered with unauthorized alternations and it is difficult to trace back the unauthorized alternations, which can result in data corruption issues. 
     Therefore, more secure and efficient solutions for implementing electronic trading platforms would be desirable. 
     SUMMARY 
     This specification describes technologies for dynamically determining values of digital tickets using smart contracts in a blockchain network. These technologies generally involve determining a current value of a digital ticket (e.g., an electronic coupon) based on one or more value changing rules using a smart contract from a blockchain network. In some embodiments, a client can submit a request to a ticket distributing node (e.g., an electronic trading platform) to redeem a digital ticket having an original value, where the request includes the digital ticket and one or more value changing rules specified by the user. The one or more value changing rules can include predetermined rules for determining a current value of the digital ticket based on factors such as a date to redeem the digital ticket, or a location to redeem to digital ticket. For example, a digital ticket can have different current values when it is redeemed at different dates, or at different locations. The ticket distributing node receives the request from the client and retrieves a smart contract from the blockchain network. The smart contract includes a number of value changing rules. The one or more value changing rules specified by the user in the request is a subset of the value changing rules in the smart contract. The ticket distributing node can then execute the smart contract to determine a current value of the digital ticket by applying the one or more value changing rules on the original value of the digital ticket. 
     This specification also provides one or more non-transitory computer-readable storage media coupled to one or more processors and having instructions stored thereon which, when executed by the one or more processors, cause the one or more processors to perform operations in accordance with embodiments of the methods provided herein. 
     This specification further provides a system for implementing the methods provided herein. The system includes one or more processors, and a computer-readable storage medium coupled to the one or more processors having instructions stored thereon which, when executed by the one or more processors, cause the one or more processors to perform operations in accordance with embodiments of the methods provided herein. 
     It is appreciated that methods in accordance with this specification may include any combination of the aspects and features described herein. That is, methods in accordance with this specification are not limited to the combinations of aspects and features specifically described herein, but also include any combination of the aspects and features provided. 
     The details of one or more embodiments of this specification are set forth in the accompanying drawings and the description below. Other features and advantages of this specification will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating an example of an environment that can be used to execute embodiments of this specification. 
         FIG. 2  is a diagram illustrating an example of a conceptual architecture in accordance with embodiments of this specification. 
         FIG. 3  is a diagram illustrating an example of a system in accordance with embodiments of this specification. 
         FIG. 4  depicts an example of a signal flow in accordance with embodiments of this specification. 
         FIG. 5  depicts an example of a process that can be executed in accordance with embodiments of this specification. 
         FIG. 6  depicts examples of modules of an apparatus in accordance with embodiments of this specification. 
     
    
    
     Like reference numbers and designations in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
     This specification describes technologies for dynamically determining values (e, g, a discount rate, a monetary value) of digital tickets (e.g., an electronic discount coupon, an electronic voucher, an electronic gift certificate) using smart contracts from a blockchain network. These technologies generally involve determining a current value of a digital ticket based on one or more value changing rules using a smart contract from a blockchain network. In some embodiments, a client can submit a request to a ticket distributing node (e.g., an electronic trading platform) to redeem a digital ticket having an original value, where the request includes the digital ticket and one or more value changing rules specified by the user. The one or more value changing rules can include predetermined rules for determining a current value of the digital ticket based on factors such as a date to redeem the digital ticket, or a location to redeem to digital ticket. For example, a digital ticket can have different current values when it is redeemed at different dates, or at different locations. The ticket distributing node receives the request from the client and retrieves a smart contract from the blockchain network. The smart contract includes a number of value changing rules. The one or more value changing rules specified by the user in the request is a subset of the value changing rules in the smart contract. The ticket distributing node can then execute the smart contract to determine a current value of the digital ticket by applying the one or more value changing rules on the original value of the digital ticket. 
     The embodiments described in this specification as implemented in particular embodiments realize one or more of the following technical effects. The values of digital tickets can be dynamically determined based on different value changing rules specified by users. In some embodiments, a digital ticket can reach a maximum value at different dates, or at different locations based on the value changing rules specified by the users in the request. This facilitates encouraging the users to redeem the digital tickets at different dates or locations, thereby alleviating the pressure on the computer systems that process the requests from the users to redeem the digital tickets. Furthermore, the values of the digital tickets can be determined using a smart contract from the blockchain network. The smart-contract can be used to implement trusted transactions that are trackable, irreversible, and tamper resistant, without involving the third parties. This ensures a secure and trusted value determining process for the digital tickets. The autonomous execution capacities of smart contracts extends the transactional security assurance of blockchain into situations where complex and dynamic value retrieval of the digital tickets are needed. In some cases, the smart contracts can be executed without a third party (e.g., without an arbitrating program or an intermediary program) in between the clients and the distributing node for retrieving values of the digital tickets. This approach can save computing and network resources (e.g., network bandwidth) for the value retrieval process. 
     To provide further context for embodiments of this specification, and as introduced above, distributed ledger systems (DLSs), which can also be referred to as consensus networks (e.g., made up of peer-to-peer nodes), and blockchain networks, enable participating entities to securely, and immutably conduct transactions, and store data. Although the term blockchain is generally associated with particular networks, and/or use cases, blockchain is used herein to generally refer to a DLS without reference to any particular use case. 
     A blockchain is a data structure that stores transactions in a way that the transactions are immutable. Thus, transactions recorded on a blockchain are reliable and trustworthy. A blockchain includes one or more blocks. Each block in the chain is linked to a previous block immediately before it in the chain by including a cryptographic hash of the previous block. Each block also includes a timestamp, its own cryptographic hash, and one or more transactions. The transactions, which have already been verified by the nodes of the blockchain network, are hashed and encoded into a Merkle tree. A Merkle tree is a data structure in which data at the leaf nodes of the tree is hashed, and all hashes in each branch of the tree are concatenated at the root of the branch. This process continues up the tree to the root of the entire tree, which stores a hash that is representative of all data in the tree. A hash purporting to be of a transaction stored in the tree can be quickly verified by determining whether it is consistent with the structure of the tree. 
     Whereas a blockchain is a decentralized or at least partially decentralized data structure for storing transactions, a blockchain network is a network of computing nodes that manage, update, and maintain one or more blockchains by broadcasting, verifying and validating transactions, etc. As introduced above, a blockchain network can be provided as a public blockchain network, a private blockchain network, or a consortium blockchain network. Embodiments of this specification are described in further detail herein with reference to a consortium blockchain network. It is contemplated, however, that embodiments of this specification can be realized in any appropriate type of blockchain network. 
     In general, a consortium blockchain network is private among the participating entities. In a consortium blockchain network, the consensus process is controlled by an authorized set of nodes, which can be referred to as consensus nodes, one or more consensus nodes being operated by a respective entity (e.g., a financial institution, insurance company). For example, a consortium of ten (10) entities (e.g., financial institutions, insurance companies) can operate a consortium blockchain network, each of which operates at least one node in the consortium blockchain network. 
     In some examples, within a consortium blockchain network, a global blockchain is provided as a blockchain that is replicated across all nodes. That is, all consensus nodes are in perfect state consensus with respect to the global blockchain. To achieve consensus (e.g., agreement to the addition of a block to a blockchain), a consensus protocol is implemented within the consortium blockchain network. For example, the consortium blockchain network can implement a practical  Byzantine  fault tolerance (PBFT) consensus, described in further detail below. 
       FIG. 1  is a diagram illustrating an example of an environment  100  that can be used to execute embodiments of this specification. In some examples, the environment  100  enables entities to participate in a consortium blockchain network  102 . The environment  100  includes computing devices  106 ,  108 , and a network  110 . In some examples, the network  110  includes a local area network (LAN), wide area network (WAN), the Internet, or a combination thereof, and connects web sites, user devices (e.g., computing devices), and back-end systems. In some examples, the network  110  can be accessed over a wired and/or a wireless communications link. In some examples, the network  110  enables communication with, and within the consortium blockchain network  102 . In general the network  110  represents one or more communication networks. In some cases, the computing devices  106 ,  108  can be nodes of a cloud computing system (not shown), or each computing device  106 ,  108  can be a separate cloud computing system including a number of computers interconnected by a network and functioning as a distributed processing system. 
     In the depicted example, the computing devices  106 ,  108  can each include any appropriate computing system that enables participation as a node in the consortium blockchain network  102 . Examples of computing devices include, without limitation, a server, a desktop computer, a laptop computer, a tablet computing device, and a smartphone. In some examples, the computing devices  106 ,  108  host one or more computer-implemented services for interacting with the consortium blockchain network  102 . For example, the computing device  106  can host computer-implemented services of a first entity (e.g., user A), such as a transaction management system that the first entity uses to manage its transactions with one or more other entities (e.g., other users). The computing system  108  can host computer-implemented services of a second entity (e.g., user B), such as a transaction management system that the second entity uses to manage its transactions with one or more other entities (e.g., other users). In the example of  FIG. 1 , the consortium blockchain network  102  is represented as a peer-to-peer network of nodes, and the computing devices  106 ,  108  provide nodes of the first entity, and second entity respectively, which participate in the consortium blockchain network  102 . 
       FIG. 2  depicts an example of a conceptual architecture  200  in accordance with embodiments of this specification. The conceptual architecture  200  includes participant systems  202 ,  204 ,  206  that correspond to Participant A, Participant B, and Participant C, respectively. Each participant (e.g., user, enterprise) participates in a blockchain network  212  provided as a peer-to-peer network including a plurality of nodes  214 , at least some of which immutably record information in a blockchain  216 . Although a single blockchain  216  is schematically depicted within the blockchain network  212 , multiple copies of the blockchain  216  are provided, and are maintained across the blockchain network  212 , as described in further detail herein. 
     In the depicted example, each participant system  202 ,  204 ,  206  is provided by, or on behalf of Participant A, Participant B, and Participant C, respectively, and functions as a respective node  214  within the blockchain network. As used herein, a node generally refers to an individual system (e.g., computer, server) that is connected to the blockchain network  212 , and enables a respective participant to participate in the blockchain network. In the example of  FIG. 2 , a participant corresponds to each node  214 . It is contemplated, however, that a participant can operate multiple nodes  214  within the blockchain network  212 , and/or multiple participants can share a node  214 . In some examples, the participant systems  202 ,  204 ,  206  communicate with, or through the blockchain network  212  using a protocol (e.g., hypertext transfer protocol secure (HTTPS)), and/or using remote procedure calls (RPCs). 
     Nodes  214  can have varying degrees of participation within the blockchain network  212 . For example, some nodes  214  can participate in the consensus process (e.g., as miner nodes that add blocks to the blockchain  216 ), while other nodes  214  do not participate in the consensus process. As another example, some nodes  214  store a complete copy of the blockchain  216 , while other nodes  214  only store copies of portions of the blockchain  216 . For example, data access privileges can limit the blockchain data that a respective participant stores within its respective system. In the example of  FIG. 2 , the participant systems  202 ,  204  store respective, complete copies  216 ′,  216 ″ of the blockchain  216 . 
     A blockchain (e.g., the blockchain  216  of  FIG. 2 ) is made up of a chain of blocks, each block storing data. Examples of data include transaction data representative of a transaction between two or more participants. While transactions are used herein by way of non-limiting example, it is contemplated that any appropriate data can be stored in a blockchain (e.g., documents, images, videos, audio). Examples of a transaction can include, without limitation, exchanges of something of value (e.g., assets, products, services, currency). The transaction data is immutably stored within the blockchain. That is, the transaction data cannot be changed. 
     Before storing in a block, the transaction data is hashed. Hashing is a process of transforming the transaction data (provided as string data) into a fixed-length hash value (also provided as string data). It is not possible to un-hash the hash value to obtain the transaction data. Hashing ensures that even a slight change in the transaction data results in a completely different hash value. Further, and as noted above, the hash value is of fixed length. That is, no matter the size of the transaction data the length of the hash value is fixed. Hashing includes processing the transaction data through a hash function to generate the hash value. An example of a hash function includes, without limitation, the secure hash algorithm (SHA)-256, which outputs 256-bit hash values. 
     Transaction data of multiple transactions are hashed and stored in a block. For example, hash values of two transactions are provided, and are themselves hashed to provide another hash. This process is repeated until, for all transactions to be stored in a block, a single hash value is provided. This hash value is referred to as a Merkle root hash, and is stored in a header of the block. A change in any of the transactions will result in change in its hash value, and ultimately, a change in the Merkle root hash. 
     Blocks are added to the blockchain through a consensus protocol. Multiple nodes within the blockchain network participate in the consensus protocol, and perform work to have a block added to the blockchain. Such nodes are referred to as consensus nodes. PBFT, introduced above, is used as a non-limiting example of a consensus protocol. The consensus nodes execute the consensus protocol to add transactions to the blockchain, and update the overall state of the blockchain network. 
     In further detail, the consensus node generates a block header, hashes all of the transactions in the block, and combines the hash value in pairs to generate further hash values until a single hash value is provided for all transactions in the block (the Merkle root hash). This hash is added to the block header. The consensus node also determines the hash value of the most recent block in the blockchain (i.e., the last block added to the blockchain). The consensus node also adds a nonce value, and a timestamp to the block header. 
     In general, PBFT provides a practical  Byzantine  state machine replication that tolerates  Byzantine  faults (e.g., malfunctioning nodes, malicious nodes). This is achieved in PBFT by assuming that faults will occur (e.g., assuming the existence of independent node failures, and/or manipulated messages sent by consensus nodes). In PBFT, the consensus nodes are provided in a sequence that includes a primary consensus node, and backup consensus nodes. The primary consensus node is periodically changed, Transactions are added to the blockchain by all consensus nodes within the blockchain network reaching an agreement as to the world state of the blockchain network. In this process, messages are transmitted between consensus nodes, and each consensus nodes proves that a message is received from a specified peer node, and verifies that the message was not modified during transmission. 
     In PBFT, the consensus protocol is provided in multiple phases with all consensus nodes beginning in the same state. To begin, a client sends a request to the primary consensus node to invoke a service operation (e.g., execute a transaction within the blockchain network). In response to receiving the request, the primary consensus node multicasts the request to the backup consensus nodes. The backup consensus nodes execute the request, and each sends a reply to the client. The client waits until a threshold number of replies are received. In some examples, the client waits for f+1 replies to be received, where f is the maximum number of faulty consensus nodes that can be tolerated within the blockchain network. The final result is that a sufficient number of consensus nodes come to an agreement on the order of the record that is to be added to the blockchain, and the record is either accepted, or rejected. 
     The blockchain networks as described herein can be used for implementing electronic trading systems or platforms. The electronic trading systems may distribute digital tickets (e.g., electronic coupons) to consumers for promotional purposes. The digital tickets can have a value (e.g., a discount rate of a discount coupon, or a monetary value of an electronic voucher) which can be redeemed by consumers for purchasing products or services on an electronic trading platform.  FIG. 3  is a diagram illustrating an example of a system  300  that retrieves a current value of a digital ticket using a smart contract from a blockchain network. As shown, the system  300  includes a blockchain network  302 , a deploying server  304 , a distributing node  306 , and clients  308  (e.g., client computing devices). In general, the deploying server  304  deploys smart contracts  310  to the blockchain network  302  and the distributing node  306  distributes digital tickets  312  to the clients  308 . The digital tickets  312  are generated based on the smart contracts  310  such that values of the digital tickets  312  can be dynamically determined by executing value changing rules in the smart contracts  310 . 
     The deploying server  304  can be any suitable server, computer, module, or computing element programmed to perform the methods described in this specification. In some embodiments, the deploying server  304  in operation creates the smart contracts  310  and deploys the smart contracts  310  to the blockchain network  302 . In some embodiments, the deploying server  304  can set up one or more dynamic ticket templates in the smart contracts  310  that can be used for creating the digital tickets  312 . The deploying server  304  can define rules in the dynamic ticket templates for dynamically determining values of the digital tickets  312 . The deploying server  304  can further add more templates to the smart contracts  310  upon request. Some examples of the rules in the smart contract  310  include increasing value of a digital ticket  312  as time passes, assigning a certain value to the digital ticket during a specified time period, among others. 
     The distributing node  306  can generate digital tickets  312  based on the smart contracts  310 . In some examples, the distributing node  306  can register accounts in a smart contract  310  and use the dynamic ticket templates in the smart contract  310  to generate the digital tickets  312 . In some examples, a digital ticket  312  can have a form of an electronic voucher, a digital token, or an electronic coupon, among others. Each digital ticket  312  can includes one or more rules for determining the values of the digital ticket  312 . After generation, the digital tickets  312  can be stored in the blockchain network  302  in a distributed manner. 
     The clients  308  can request (e.g., purchase) one or more of digital tickets  312  from the distributing node  306  and obtain the digital tickets  312 . In some examples, the clients  308  can inspect each of the digital tickets  312  for the rules included in each of the digital tickets  312 . The clients  308  can choose one or more of the rules in a digital ticket  312  to apply to a digital ticket  312  for a value of the digital ticket  312 . In some embodiments, the clients  308  can submit a request to the distributing node  306  for redeeming a value of a digital ticket  312  and the distributing node  306  can make a smart contract call to determine the value of the digital ticket  312 . 
     In operation, the deploying server  304  generates smart contracts  310  that each include one or more dynamic ticket templates and deploys the smart contracts  310  to the blockchain network  302 . The distributing node  306  registers account in the smart contracts  310  and generates digital tickets  312  based on the smart contracts  310 . The distributing node  306  distributes the digital tickets to the clients  308 . The clients  308  obtain the digital tickets  312  and inspect rules in the digital tickets  312 . Each client  308  selects one or more of the rules that are applied to the digital ticket  312  for determining a value of the digital ticket  312 . The client  308  submits the digital ticket  312  and the selected rule(s) to the distributing node  306  for redeeming the value of the digital ticket  312 . The distributing node  306  receives the digital ticket  312  along with the selected rule(s) and makes a smart contract call. The distributing node  306  uses the called smart contract  310  and the selected rule(s) to determine the value of the digital ticket  312 . The distributing node  306  endows the determined value to the digital ticket  312  and the client  308  can use the endowed ticket. The value determination of the digital tickets  312  will be discussed below in greater detail with reference to  FIG. 4 . 
     In some embodiments, distributing entities that distribute the digital tickets  312  and receiving entities that receive the digital tickets  312  are entities that are defined in the smart contracts  310  and that are external to the blockchain network. In some examples, values of the digital tickets  312  increase or decrease linearly based on the rules of the digital tickets  312 . For example, a digital ticket  312  can be an electronic discount coupon having an original discount rate of 95%, and the original discount rate can decrease by 5% a week until it reaches a predetermined threshold, for example, 60%. In some examples, a digital ticket  312  can have different values at different time points or periods. For example, a digital ticket  312  can be an electronic voucher having a first monetary value of $10 in January, a second monetary value of $5 in February, and a third monetary value of $15 in March. 
       FIG. 4  depicts an example of a signal flow  400  in accordance with embodiments of this specification. The signal flow  400  represents an example a process for determining the value of a digital ticket. For convenience, the process will be described as being performed by a system of one or more computers, located in one or more locations, and programmed appropriately in accordance with this specification. For example, a distributed system (e.g., the environment  100  of  FIG. 1 ; the system  300  of  FIG. 3 ), appropriately programmed, can perform the process. 
     The deploying server  304  generates ( 402 ) smart contracts  310 . In some embodiments, the deploying server  304  sets up one or more dynamic ticket templates in one or more of the smart contracts  310  that can be used for creating the digital tickets  312 . The deploying server  304  can further define rules in the dynamic ticket templates for dynamically determining values of the digital tickets  312 . The deploying server  304  can further add more templates to the smart contracts  310  upon request. In some templates, the rules in the templates include value changing rules for changing the value of a digital ticket  312  generated from the templates, such as rules that associate a growth rate with the value of a digital ticket  312 , rules that associate a date with the value of a digital ticket  312 , and/or rules that associate a location with the value of a digital ticket  312 . Some examples of the rules in the smart contract  310  include increasing the value of a digital ticket  312  as time passes, assigning a certain value to a digital ticket  312  during a specified time period, among others. 
     The deploying server  304  deploys ( 404 ) the smart contracts  310  to the blockchain network. In some examples, the deploying server  304  generates and submits a transaction of smart contract to the blockchain network  302 . The transaction of smart contract  310  may include a program and an originator of the smart contract  310 . The mining nodes (miners) of the blockchain network  302  verify the transaction of the smart contract  310 . After the mining nodes successfully verify the transaction of the smart contract  310 , the smart contract  310  can be deployed in the blockchain network  302  in a distributed manner and has a unique smart contract address from which the smart contract  310  can be called. 
     In some embodiments, the distributing node  306  accesses ( 406 ) the blockchain network  302  and obtains the smart contract  310 . The distributing node  306  processes the smart contract  310  and registers (creates) an account with the smart contract  310 . In some examples, the distributing node  306  generates ( 408 ) digital tickets  312  based on the smart contract  310 . As noted, the smart contract  310  includes a dynamic ticket template defining a plurality of rules for determining values of the digital tickets  312 . The distributing node  306  can use one or more of the rules for creating a digital ticket  312 , such that different ticket  312  may be associated with different subsets of the rules. For example, one digital ticket  312  may be associated with a rule that increases the value of the ticket  312  over time from when the ticket  312  is submitted for redeeming the ticket. As another example, another digital ticket  312  may be associated with another rule that endows the ticket  312  a maximum value during a specified time window. 
     In some embodiments, the digital tickets  312  are stored in the blockchain network  302  in a distributed manner. In some examples, a digital ticket  312  has an original value. Each digital ticket  312  is associated with one or more of the rules. In some examples, the rules are assigned to the digital ticket  312  during creation of the tickets  312 , or can be assigned to the digital ticket  312  by an operator after the creation of the tickets  312 . In some embodiments, the rules that are assigned to a digital ticket  312  may not be tampered with or invalidated. In some examples, the rules that are assigned to a digital ticket  312  may be tampered or invalidated upon approval of a certificate authority. Different rules and/or subsets of the rules that are assigned to the digital tickets  312  reflect different value endowments of the tickets  312 . A client  308  can select one or more of the rules associated with a digital ticket  312  when the client  308  redeems the digital ticket  312 . 
     In some embodiments, the distributing node  306  can apply value change strategy on the rules of the digital tickets  312 . In some examples, the value change strategy allows the value of the digital tickets  312  to change based on time. For example, rules based on the value change strategy can allow value of a digital ticket  312  to increase gradually over time until reaching a maximum value. A client  308  selecting such rule for redeeming the digital ticket  312  can wait until the value of the digital ticket  312  to be the maximum to obtain a full value of the ticket  312 . As another example, rules based on the value change strategy can allow value of a digital ticket  312  to be a certain value during a specified time window. For example, the value of the digital ticket  312  can have a maximum value during a specified time window but has only a fraction of the maximum value outside the time window. A client  308  selecting such rule for the digital ticket  312  can redeem the digital ticket  312  during the specified time window to obtain a full value of the ticket  312 . In some embodiments, the value change strategy allows the rules to associate a growth rate with the value of the digital tickets  312 . For examples, the value of a digital ticket  312  associated with the rules can increases over time with a specified growth rate. In some embodiments, the value change strategy allows the rules to associate a date with the value of the digital tickets  312 . For example, the value of a digital ticket  312  associated with the rules can have a value at a specified date. In some embodiments, the value change strategy allows the rules to associate a location with the value of the digital tickets  312 . For example, the value of a digital ticket  312  associated with the rules can have a value at a specified location. 
     In some embodiments, the distributing node  306  can apply correlation value change strategy on the rules of the digital tickets  312  when generating the digital tickets  312 . In some examples, rules based on the correlation value change strategy can allow other values that are correlated to the value of the digital ticket  312  to change with time or location or other factors. In some embodiments, the distributing node  306  can add additional rules to the digital ticket  312  after the generation of the tickets  312 . In some examples, the additional rules can include rules that change the value of the digital tickets  312 , and rules that associate other digital tickets  312  to an existing digital ticket  312  and that assign the associated digital tickets  312  to client  308  who holds the existing digital ticket  312 . 
     The distributing node  306  publishes ( 410 ) the digital tickets  312 . In some embodiments, the distributing node  306  implements a digital distributing platform and posts the digital tickets  312  on the platform where the tickets  312  are made available to the clients  308 . As noted, the digital tickets  312  are stored in the blockchain network  302  in a distributed manner. A client  308  who wants to obtain a digital ticket  312  may send request to the distributing node  306  and obtain the digital ticket  312  from the blockchain network  302  upon approval from the distributing node  306 . 
     A client  308  requests ( 412 ) a digital ticket  312  from the distributing node  306 . As noted, the distributing node  306  may implement a digital distributing platform and the client  308  can send a request for digital tickets  312  to the digital distributing platform. In some embodiments, the distributing node  306  returns a link or an address of the requested digital tickets  312  in the blockchain network  302 . The client  308  can obtain ( 414 ) the digital tickets  312  from the blockchain network using the link or the address. 
     In some embodiments, the client  308  processes ( 416 ) the digital tickets  312  to inspect the rules for determining the value of the tickets  312 . The client  308  can select one or more of the rules of the ticket  312  for endowing a value to the ticket  312 . For example, the client  308  can select a rule that increases the value of the ticket  312  gradually over time, or can select a rule that endows a certain value to the ticket  312  during a specified time window. 
     The client  308  submits ( 418 ) the digital tickets  312  to the distributing node  306  when the client  308  redeems the digital tickets  312 . In some examples, the client  308  sends a request to the distributing node  306 , the request indicating that the client  308  wants to redeem a digital ticket  312  that the client previously obtained from the distributing node  306  and including the digital ticket  312  and one or more rules selected by the client  308 . The request can also include a timestamp indicating when the client  308  submitted the request to the distributing node  306 . 
     The distributing node  306  processes ( 420 ) the request from the client  308 . As noted, the request from the client  308  can include a digital ticket  312  and one or more rules and a timestamp. The distributing node  306  can determine the value of the digital ticket  312  based on the rules and the timestamp. In some embodiments, the distributing node  306  makes a smart contract call to a smart contract this was used for generating the digital ticket  312 . As noted, the smart contract  310  includes a dynamic ticket template that defines a number of rules for determining value of the digital ticket  312 , where the number of rules include the rules in the digital ticket  312 . The smart contract  310  executes itself using the timestamp and the rules in the smart contract that are the same as the rules that were selected by the client in the digital ticket  312 . For example, the smart contract  310  can use the timestamp to determine when the client  308  submitted the digital ticket  312  and compute a value of the digital ticket  312  using the rules based on a value change strategy. In some examples, the computed value of the digital ticket  312  can be deducted from an account of the distributing node  306  and added to an account of the client  308 , and the digital ticket  312  is successfully redeemed. 
       FIG. 5  depicts an example of a process  500  for processing a request for a current value of a digital ticket using a smart contract in a blockchain network. The process  500  may be performed using one or more computer-executable programs executed using one or more computing devices. In some examples, the process  500  can be performed by a distributed system (e.g., the environment  100  of  FIG. 1 ; the system  300  of  FIG. 3 ) for processing a request for a current value of a digital ticket. 
     Process  500  starts at  502  where a distributing node  306  receives a request from a client device  308  for a current value of a digital ticket  312 . The request indicates that the client device  308  wants to redeem the digital ticket  312  and obtain the current value of the digital ticket  312 . In some embodiment, the request can include the digital ticket  312  and one or more value changing rules for determining the current value of the digital ticket  312 . In some embodiments, the one or more value changing rules can include a value changing rule that associates a growth rate with the current value of the digital ticket, a value changing rule that associates a date with the current value of the digital ticket, and/or or a value changing rule that associates a location with the current value of the digital ticket. 
     In some embodiments, the digital ticket  312  is associated with multiple value changing rules and the client device  308  can specify one or more of the multiple value changing rules and include them in the request. In some embodiments, the request further includes a timestamp indicating when the client device  308  submits the request to the distributing node  306 . 
     In some embodiments, the digital ticket  312  has an original value. For example, the digital ticket  312  can be an electronic discount coupon having an original discount value of 90%. As another example, the digital ticket  312  can be an electronic voucher having an original monetary value of $10. 
     At  504 , the distributing node  306  retrieves a smart contract  310  from a blockchain network  302  in response to receiving the request from the client device  308 . In some embodiments, the distributing node is located external to the blockchain network  302  and can communicate with the blockchain network  302  via a network connection. In some embodiments, the distributing node  306  makes a contract call to the smart contract  310  from the blockchain network  302 . In some embodiments, the smart contract  310  includes a number of value changing rules and the one or more changing rules in the request is a subset of the number of value changing rules. 
     At  506 , the distributing node  306  determines the current value of the digital ticket  312  based on the original value of the digital ticket  312  and one or more value changing rules by executing the smart contract  310 . In some embodiments, the distributing node  306  executes the smart contract  310  using the original value of the digital ticket  312  and the one or more value changing rules specified in the request. In some embodiments, the distributing node  306  executes the smart contract  310  using the original value of the digital ticket  312 , the one or more value changing rules specified in the request, and a timestamp in the request. For example, the digital ticket  312  can be an electronic discount coupon having an original discount value of 90%, and the request can include a value changing rule indicating that the discount value of the digital ticket  312  decreases by 5% per week until it reaches 60%. In such case, a current discount value of the digital ticket  312  can be determined based on the original discount value, the value changing rules, the timestamp in the request, and a time point when the digital ticket  312  was distributed to the client device  308 . 
     At  508 , the distributing node  306  associates the current value of the digital ticket  312  as determined at step  506  with the digital ticket  312 . For example, the distributing node  306  can assign the current value as determined at step  506  to the digital ticket  312 . Continue with the above example, the digital ticket  312  having an original discount value of 90% can be assigned a current discount value of 75% by executing the smart contract  310  based on the original discount value, the value changing rule, the timestamp in the request, and a time point when the digital ticket  312  was distributed to the client device  308 . 
       FIG. 6  is a diagram of an example of modules of an apparatus  600  in accordance with embodiments of this specification. The apparatus  600  can be an example of an embodiment of a distributing node. In some examples, the distributing node receives a request for a current value of a digital ticket from a client and determines the value based on value changing rules using smart contract from a blockchain network. 
     The apparatus  600  can correspond to the embodiments described above, and the apparatus  600  includes the following: a receiving module  602  that receives a request from a client device for a current value of a digital ticket, wherein the request includes the digital ticket and one or more value changing rules for determining the current value of the digital ticket, wherein the digital ticket has an original value; a retrieving module  604  that retrieves a smart contract from the blockchain network in response to receiving the request from the client device, wherein the smart contract includes the one or more value changing rules for determining the current value of the digital ticket; a determining module  606  that determines the current value of the digital ticket based at least in part on the original value of the digital ticket and the one or more value changing rules by executing the smart contract; and an associating module  608  that associates the current value with the digital ticket. 
     In an optional embodiment, the request includes a timestamp of the digital ticket, and the current value of the digital ticket is determined further based on the timestamp. 
     In an optional embodiment, the one or more value changing rules include a value changing rule that associates a growth rate with the value of the digital ticket. 
     In an optional embodiment, the one or more value changing rules include a value changing rule that associates a date with the value of the digital ticket. 
     In an optional embodiment, the one or more value changing rules include a value changing rule that associates a location with the value of the digital ticket. 
     In an optional embodiment, the smart contract includes a number of value changing rules, and where the one or more value changing rules is a subset of the number of value changing rules. 
     In an optional embodiment, the distributing node is located external to the blockchain network. 
     The system, apparatus, module, or unit illustrated in the previous embodiments can be implemented by using a computer chip or an entity, or can be implemented by using a product having a certain function. A typical embodiment device is a computer, and the computer can be a personal computer, a laptop computer, a cellular phone, a camera phone, a smartphone, a personal digital assistant, a media player, a navigation device, an email receiving and sending device, a game console, a tablet computer, a wearable device, or any combination of these devices. 
     For an embodiment process of functions and roles of each module in the apparatus, references can be made to an embodiment process of corresponding steps in the previous method. Details are omitted here for simplicity. 
     Because an apparatus embodiment basically corresponds to a method embodiment, for related parts, references can be made to related descriptions in the method embodiment. The previously described apparatus embodiment is merely an example. The modules described as separate parts may or may not be physically separate, and parts displayed as modules may or may not be physical modules, may be located in one position, or may be distributed on a number of network modules. Some or all of the modules can be selected based on actual demands to achieve the objectives of the solutions of the specification. A person of ordinary skill in the art can understand and implement the embodiments of the present application without creative efforts. 
     Referring again to  FIG. 6 , it can be interpreted as illustrating an internal functional module and a structure of a digital ticket value retrieving apparatus. The digital ticket value retrieving apparatus can be an example of a distributing node configured to retrieve a current value of a digital ticket. An execution body in essence can be an electronic device, and the electronic device includes the following: one or more processors; and a memory configured to store an executable instruction of the one or more processors. 
     The techniques described in this specification produce one or more technical effects. In some embodiments, current values of digital tickets can be dynamically determined based on different value changing rules specified by users. In some embodiments, a digital ticket can reach a maximum value at different dates, or at different locations based on the value changing rules specified by the users in the request. This facilitates encouraging the users to redeem the digital tickets at different dates or locations, thereby alleviating the pressure on the computer systems that process the requests from the users to redeem the digital tickets. Furthermore, the values of the digital tickets can be determined using a smart contract from the blockchain network. The smart-contract can be used to implement trusted transactions that are trackable, irreversible, and tamper resistant, without involving the third parties. This ensures a secure and trusted value determining process for the digital tickets. The autonomous execution capacities of smart contracts extends the transactional security assurance of blockchain into situations where complex and dynamic value retrieval of the digital tickets are needed. In some cases, the smart contracts can be executed without a third party (e.g., without an arbitrating program or an intermediary program) in between the clients and the distributing node for retrieving values of the digital tickets. This approach can save computing and network resources (e.g., network bandwidth) for the value retrieval process. 
     Described embodiments of the subject matter can include one or more features, alone or in combination. For example, in a first embodiment, a distributing node receives a request from a client device for a current value of a digital ticket, the request including the digital ticket and one or more value changing rules for determining the current value of the digital ticket, wherein the digital ticket has an original value. The distributing node retrieves a smart contract from the blockchain network in response to receiving the request from the client device, the smart contract including the one or more value changing rules for determining the current value of the digital ticket. The distributing node determines the current value of the digital ticket based at least in part on the original value of the digital ticket and the one or more value changing rules by executing the smart contract, and associates the current value with the digital ticket. The foregoing and other described embodiments can each, optionally, include one or more of the following features: 
     A first feature, combinable with any of the following features, specifies that the request includes a timestamp of the digital ticket, and the current value of the digital ticket is determined further based on the timestamp. 
     A second feature, combinable with any of the following features, specifies that the one or more value changing rules include a value changing rule that associates a growth rate with the value of the digital ticket. 
     A third feature, combinable with any of the following features, specifies that the one or more value changing rules include a value changing rule that associates a date with the value of the digital ticket. 
     A fourth feature, combinable with any of the following features, specifies that the one or more value changing rules include a value changing rule that associates a location with the value of the digital ticket. 
     A fifth feature, combinable with any of the following features, specifies that the smart contract includes a number of value changing rules, and where the one or more value changing rules is a subset of the number of value changing rules. 
     A sixth feature, combinable with any of the following features, specifies that the distributing node is located external to the blockchain network. 
     Embodiments of the subject matter and the actions and operations described in this specification can be implemented in digital electronic circuitry, in tangibly-embodied computer software or firmware, in computer hardware, including the structures disclosed in this specification and their structural equivalents, or in combinations of one or more of them. Embodiments of the subject matter described in this specification can be implemented as one or more computer programs, e.g., one or more modules of computer program instructions, encoded on a computer program carrier, for execution by, or to control the operation of, data processing apparatus. For example, a computer program carrier can include one or more computer-readable storage media that have instructions encoded or stored thereon. The carrier may be a tangible non-transitory computer-readable medium, such as a magnetic, magneto optical, or optical disk, a solid state drive, a random access memory (RAM), a read-only memory (ROM), or other types of media. Alternatively, or in addition, the carrier may be an artificially generated propagated signal, e.g., a machine-generated electrical, optical, or electromagnetic signal that is generated to encode information for transmission to suitable receiver apparatus for execution by a data processing apparatus. The computer storage medium can be or be part of a machine-readable storage device, a machine-readable storage substrate, a random or serial access memory device, or a combination of one or more of them. A computer storage medium is not a propagated signal. 
     A computer program, which may also be referred to or described as a program, software, a software application, an app, a module, a software module, an engine, a script, or code, can be written in any form of programming language, including compiled or interpreted languages, or declarative or procedural languages; and it can be deployed in any form, including as a stand-alone program or as a module, component, engine, subroutine, or other unit suitable for executing in a computing environment, which environment may include one or more computers interconnected by a data communication network in one or more locations. 
     A computer program may, but need not, correspond to a file in a file system. A computer program can be stored in a portion of a file that holds other programs or data, e.g., one or more scripts stored in a markup language document, in a single file dedicated to the program in question, or in multiple coordinated files, e.g., files that store one or more modules, sub programs, or portions of code. 
     Processors for execution of a computer program include, by way of example, both general- and special-purpose microprocessors, and any one or more processors of any kind of digital computer. Generally, a processor will receive the instructions of the computer program for execution as well as data from a non-transitory computer-readable medium coupled to the processor. 
     The term “data processing apparatus” encompasses all kinds of apparatuses, devices, and machines for processing data, including by way of example a programmable processor, a computer, or multiple processors or computers. Data processing apparatus can include special-purpose logic circuitry, e.g., an FPGA (field programmable gate array), an ASIC (application specific integrated circuit), or a GPU (graphics processing unit). The apparatus can also include, in addition to hardware, code that creates an execution environment for computer programs, e.g., code that constitutes processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of them. 
     The processes and logic flows described in this specification can be performed by one or more computers or processors executing one or more computer programs to perform operations by operating on input data and generating output. The processes and logic flows can also be performed by special-purpose logic circuitry, e.g., an FPGA, an ASIC, or a GPU, or by a combination of special-purpose logic circuitry and one or more programmed computers. 
     Computers suitable for the execution of a computer program can be based on general or special-purpose microprocessors or both, or any other kind of central processing unit. Generally, a central processing unit will receive instructions and data from a read only memory or a random access memory or both. Elements of a computer can include a central processing unit for executing instructions and one or more memory devices for storing instructions and data. The central processing unit and the memory can be supplemented by, or incorporated in, special-purpose logic circuitry. 
     Generally, a computer will also include, or be operatively coupled to receive data from or transfer data to one or more storage devices. The storage devices can be, for example, magnetic, magneto optical, or optical disks, solid state drives, or any other type of non-transitory, computer-readable media. However, a computer need not have such devices. Thus, a computer may be coupled to one or more storage devices, such as, one or more memories, that are local and/or remote. For example, a computer can include one or more local memories that are integral components of the computer, or the computer can be coupled to one or more remote memories that are in a cloud network. Moreover, a computer can be embedded in another device, e.g., a mobile telephone, a personal digital assistant (PDA), a mobile audio or video player, a game console, a Global Positioning System (GPS) receiver, or a portable storage device, e.g., a universal serial bus (USB) flash drive, to name just a few. 
     Components can be “coupled to” each other by being commutatively such as electrically or optically connected to one another, either directly or via one or more intermediate components. Components can also be “coupled to” each other if one of the components is integrated into the other. For example, a storage component that is integrated into a processor (e.g., an L2 cache component) is “coupled to” the processor. 
     To provide for interaction with a user, embodiments of the subject matter described in this specification can be implemented on, or configured to communicate with, a computer having a display device, e.g., a LCD (liquid crystal display) monitor, for displaying information to the user, and an input device by which the user can provide input to the computer, e.g., a keyboard and a pointing device, e.g., a mouse, a trackball or touchpad. Other kinds of devices can be used to provide for interaction with a user as well; for example, feedback provided to the user can be any form of sensory feedback, e.g., visual feedback, auditory feedback, or tactile feedback; and input from the user can be received in any form, including acoustic, speech, or tactile input. In addition, a computer can interact with a user by sending documents to and receiving documents from a device that is used by the user; for example, by sending web pages to a web browser on a user&#39;s device in response to requests received from the web browser, or by interacting with an app running on a user device, e.g., a smartphone or electronic tablet. Also, a computer can interact with a user by sending text messages or other forms of message to a personal device, e.g., a smartphone that is running a messaging application, and receiving responsive messages from the user in return. 
     This specification uses the term “configured to” in connection with systems, apparatus, and computer program components. For a system of one or more computers to be configured to perform particular operations or actions means that the system has installed on it software, firmware, hardware, or a combination of them that in operation cause the system to perform the operations or actions. For one or more computer programs to be configured to perform particular operations or actions means that the one or more programs include instructions that, when executed by data processing apparatus, cause the apparatus to perform the operations or actions. For special-purpose logic circuitry to be configured to perform particular operations or actions means that the circuitry has electronic logic that performs the operations or actions. 
     While this specification contains many specific embodiment details, these should not be construed as limitations on the scope of what is being claimed, which is defined by the claims themselves, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in this specification in the context of separate embodiments can also be realized in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiments can also be realized in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially be claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claim may be directed to a subcombination or variation of a subcombination. 
     Similarly, while operations are depicted in the drawings and recited in the claims in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system modules and components in the embodiments described above should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. 
     Particular embodiments of the subject matter have been described. Other embodiments are within the scope of the following claims. For example, the actions recited in the claims can be performed in a different order and still achieve desirable results. As one example, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In some cases, multitasking and parallel processing may be advantageous.