U.S. patent application number 16/780334 was filed with the patent office on 2020-06-04 for verifying integrity of data stored in a consortium blockchain using a public sidechain.
This patent application is currently assigned to Alibaba Group Holding Limited. The applicant listed for this patent is Alibaba Group Holding Limited. Invention is credited to Long Cheng, Zhiyuan Feng, Yanpeng Li.
Application Number | 20200175207 16/780334 |
Document ID | / |
Family ID | 66100041 |
Filed Date | 2020-06-04 |
United States Patent
Application |
20200175207 |
Kind Code |
A1 |
Cheng; Long ; et
al. |
June 4, 2020 |
VERIFYING INTEGRITY OF DATA STORED IN A CONSORTIUM BLOCKCHAIN USING
A PUBLIC SIDECHAIN
Abstract
Implementations of the present specification include storing a
data item in a consortium blockchain; generating a first data
digest based on the stored data item; sending the first data digest
to verification nodes to cryptographically signs it and stores the
signed first data digest in a public blockchain; receiving a
request to retrieve the stored data item; retrieving the requested
data item from the consortium blockchain; generating a second data
digest based on the retrieved data item; sending the second data
digest to verification nodes so that each verification node signs
the second data digest; receiving the signed second data digests
from the plurality of verification nodes; retrieving the signed
first data digests from the public blockchain; determining that the
signed first data digests match the signed second data digests; and
sending a response indicating the stored data item is unchanged to
the request to retrieve the stored data item.
Inventors: |
Cheng; Long; (Hangzhou,
CN) ; Li; Yanpeng; (Hangzhou, CN) ; Feng;
Zhiyuan; (Hangzhou, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Alibaba Group Holding Limited |
George Town |
|
KY |
|
|
Assignee: |
Alibaba Group Holding
Limited
George Town
KY
|
Family ID: |
66100041 |
Appl. No.: |
16/780334 |
Filed: |
February 3, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16421357 |
May 23, 2019 |
10552641 |
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16780334 |
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PCT/CN2018/122559 |
Dec 21, 2018 |
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16421357 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G06F 21/645 20130101;
H04L 9/0637 20130101; H04L 2209/38 20130101; G06F 21/602 20130101;
H04L 9/00 20130101; H04L 9/0643 20130101; G06Q 20/10 20130101; G06F
21/64 20130101; H04L 9/3247 20130101; H04L 9/3239 20130101; G06F
21/6236 20130101 |
International
Class: |
G06F 21/64 20060101
G06F021/64; H04L 9/32 20060101 H04L009/32; H04L 9/06 20060101
H04L009/06; G06Q 20/10 20060101 G06Q020/10; G06F 21/60 20060101
G06F021/60; H04L 9/00 20060101 H04L009/00 |
Claims
1. A computer-implemented method, comprising: sending, to each of a
plurality of verification nodes, a first data digest generated
based on a data item initially stored in a consortium blockchain,
the first data digest being cryptographically signed and stored in
a public blockchain as a cryptographically signed first data
digest; receiving a request to retrieve the data item; generating,
based upon the request to retrieve the data item, a second data
digest based on the data item; sending the second data digest to
the plurality of verification nodes that cryptographically sign the
second data digest and return a cryptographically signed second
data digest; and based upon the stored cryptographically signed
first data digest matching the returned cryptographically signed
second data digest, sending a response to the request to retrieve
the data item indicating that the data item has not changed since
the data item was initially stored in the consortium
blockchain.
2. The computer-implemented method of claim 1, wherein the
plurality of verification nodes are computing devices participating
in the public blockchain.
3. The computer-implemented method of claim 1, further comprising:
storing, in the public blockchain, a smart contract configured to
provide a monetary reward to the verification nodes in response to
receiving the cryptographically signed second data digest from the
verification nodes.
4. The computer-implemented method of claim 1, wherein the first
data digest is generated using a hash of the initially stored data
item.
5. The computer-implemented method of claim 1, wherein each
verification node is configured to cryptographically sign the first
data digest using a private key associated with that verification
node.
6. The computer-implemented method of claim 1, wherein sending the
first data digest to the plurality of verification nodes includes
broadcasting the first data digest to a public blockchain network
that manages the public blockchain.
7. The computer-implemented method of claim 1, further comprising:
identifying the cryptographically signed first data digest stored
in the public blockchain based on an identifier associated with the
data item; and retrieving the cryptographically signed first data
digest from the public blockchain.
8. A non-transitory computer-readable storage medium storing one or
more instructions executable by a computer system to perform
operations comprising: sending, to each of a plurality of
verification nodes, a first data digest generated based on a data
item initially stored in a consortium blockchain, the first data
digest being cryptographically signed and stored in a public
blockchain as a cryptographically signed first data digest;
receiving a request to retrieve the data item; generating, based
upon the request to retrieve the data item, a second data digest
based on the data item; sending the second data digest to the
plurality of verification nodes that cryptographically sign the
second data digest and return a cryptographically signed second
data digest; and based upon the stored cryptographically signed
first data digest matching the returned cryptographically signed
second data digest, sending a response to the request to retrieve
the data item indicating that the data item has not changed since
the data item was initially stored in the consortium
blockchain.
9. The non-transitory computer-readable storage medium of claim 8,
wherein the plurality of verification nodes are computing devices
participating in the public blockchain.
10. The non-transitory computer-readable storage medium of claim 8,
wherein the operations comprise: storing, in the public blockchain,
a smart contract configured to provide a monetary reward to the
verification nodes in response to receiving the cryptographically
signed second data digest from the verification nodes.
11. The non-transitory computer-readable storage medium of claim 8,
wherein the first data digest is generated using a hash of the data
item.
12. The non-transitory computer-readable storage medium of claim 8,
wherein each verification node is configured to cryptographically
sign the first data digest using a private key associated with that
verification node.
13. The non-transitory computer-readable storage medium of claim 8,
wherein sending the first data digest to the plurality of
verification nodes includes broadcasting the first data digest to a
public blockchain network that manages the public blockchain.
14. The non-transitory computer-readable storage medium of claim 8,
wherein the operations comprise: identifying the cryptographically
signed first data digest stored in the public blockchain based on
an identifier associated with the data item; and retrieving the
cryptographically signed first data digest from the public
blockchain.
15. A system, comprising: one or more computers; and one or more
computer memory devices interoperably coupled with the one or more
computers and having tangible, non-transitory, machine-readable
media storing one or more instructions that, when executed by the
one or more computers, perform one or more operations comprising:
sending, to each of a plurality of verification nodes, a first data
digest generated based on a data item initially stored in a
consortium blockchain, the first data digest being
cryptographically signed and stored in a public blockchain as a
cryptographically signed first data digest; receiving a request to
retrieve the data item; generating, based upon the request to
retrieve the data item, a second data digest based on the data
item; sending the second data digest to the plurality of
verification nodes that cryptographically sign the second data
digest and return a cryptographically signed second data digest;
and based upon the stored cryptographically signed first data
digest matching the returned cryptographically signed second data
digest, sending a response to the request to retrieve the data item
indicating that the data item has not changed since the data item
was initially stored in the consortium blockchain.
16. The system of claim 15, wherein the plurality of verification
nodes are computing devices participating in the public
blockchain.
17. The system of claim 15, wherein the operations further
comprise: storing, in the public blockchain, a smart contract
configured to provide a monetary reward to the verification nodes
in response to receiving the cryptographically signed second data
digest from the verification nodes.
18. The system of claim 15, wherein each verification node is
configured to cryptographically sign the first data digest using a
private key associated with that verification node.
19. The system of claim 15, wherein sending the first data digest
to the plurality of verification nodes includes broadcasting the
first data digest to a public blockchain network that manages the
public blockchain.
20. The system of claim 15, wherein the operations further
comprise: identifying the cryptographically signed first data
digest stored in the public blockchain based on an identifier
associated with the data item; and retrieving the cryptographically
signed first data digest from the public blockchain.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 16/421,357, filed on May 23, 2019, which is a
continuation of PCT Application No. PCT/CN2018/122559, filed on
Dec. 21, 2018, and each application is hereby incorporated by
reference in its entirety.
BACKGROUND
[0002] 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 public
blockchain network is open for all entities to use the DLS, and
participate in the consensus process. A private blockchain network
is provided for particular entity, which centrally controls read
and write permissions. A consortium blockchain network is provided
for a select group of entities, which control the consensus
process, and includes an access control layer.
[0003] Blockchain is a decentralized and temper-proof distributed
data storage technology. User data and contracts are logically
operated and stored on the chain in a public manner. In many
scenarios, users need to meet privacy protection requirements and
do not want their data and logics to be leaked to unauthorized
parties.
[0004] Although cryptography can be used to enhance privacy
protection for some specific scenario designs, a more versatile and
efficient solution is desired to solve existing privacy issues of
the blockchain operations.
SUMMARY
[0005] Implementations of the present specification include
computer-implemented methods for storing and retrieving
to-be-verified data associated with nodes of a blockchain network.
More particularly, implementations of the present specification are
directed to storing a data digest of the to-be-verified data
associated with one or more consortium blockchain network nodes
using a number of verification nodes, and retrieving the
to-be-verified data and the stored data digests.
[0006] In some implementations, actions include storing a data item
in a consortium blockchain maintained by a consortium blockchain
network; generating a first data digest based on the stored data
item; sending the first data digest to verification nodes, so that
each verification node cryptographically signs the first data
digest and stores its signed first data digest in a public
blockchain maintained by a public blockchain network; receiving a
request to retrieve the stored data item; in response to receiving
the request, retrieving the requested data item from the consortium
blockchain; generating a second data digest based on the retrieved
data item; sending the second data digest to the verification nodes
so that each verification node cryptographically signs the second
data digest and returns its signed second data digest; receiving
the signed second data digests from the verification nodes;
retrieving the signed first data digests from the public
blockchain; determining that the signed first data digests match
the signed second data digests; and in response to the determining,
sending a response to the request to retrieve the stored data item,
the response indicating that the stored data item has not changed
since it was stored. Other implementations include corresponding
systems, apparatus, and computer programs, configured to perform
the actions of the methods, encoded on computer storage
devices.
[0007] In some implementations, a non-transitory computer-readable
storage medium is coupled to one or more computers and configured
with instructions executable by the one or more computers to: store
a data item in a consortium blockchain maintained by a consortium
blockchain network; generate a first data digest based on the
stored data item; send the first data digest to verification nodes
so that each verification node cryptographically signs the first
data digest and stores its signed first data digest in a public
blockchain maintained by a public blockchain network; receive a
request to retrieve the stored data item; in response to receive
the request, retrieving the requested data item from the consortium
blockchain; generate a second data digest based on the retrieved
data item; send the second data digest to verification nodes so
that each verification node cryptographically signs the second data
digest and returns its signed second data digest; receive the
signed second data digests from the verification nodes; retrieve
the signed first data digests from the public blockchain; determine
that the signed first data digests match the signed second data
digests; and in response to the determine, sending a response to
the request to retrieve the stored data item, the response
indicating that the stored data item has not changed since it was
stored.
[0008] In some implementations, a system includes one or more
computers; and one or more computer-readable memories coupled to
the one or more computers and configured with instructions
executable by the one or more computers to: store a data item in a
consortium blockchain maintained by a consortium blockchain
network; generate a first data digest based on the stored data
item; send the first data digest to verification nodes so that each
verification node cryptographically signs the first data digest and
stores its signed first data digest in a public blockchain
maintained by a public blockchain network; receive a request to
retrieve the stored data item; in response to receive the request,
retrieving the requested data item from the consortium blockchain;
generate a second data digest based on the retrieved data item;
send the second data digest to verification nodes so that each
verification node cryptographically signs the second data digest
and returns its signed second data digest; receive the signed
second data digests from the verification nodes; retrieve the
signed first data digests from the public blockchain; determine
that the signed first data digests match the signed second data
digests received; and in response to the determine, sending a
response to the request to retrieve the stored data item, the
response indicating that the stored data item has not changed since
it was stored. These and other implementations may each optionally
include one or more of the following features:
[0009] A first feature, combinable with any of the following
features, wherein the verification nodes are computing devices
participating in the public blockchain network.
[0010] A second feature, combinable with any of the following
features, further includes storing a smart contract in the public
blockchain, wherein the smart contract is configured to provide a
monetary reward to the verification nodes in response to receiving
the requested signed second data digests from the verification
nodes.
[0011] A third feature, combinable with any of the following
features, wherein generating the first data digest includes
calculating a hash of the stored data item.
[0012] A fourth feature, combinable with any of the following
features, wherein each verification node is configured to
cryptographically sign the first data digest using a private key
associated with that verification node.
[0013] A fifth feature, combinable with any of the following
features, wherein sending the first data digest to the verification
nodes includes broadcasting the first data digest to the public
blockchain network.
[0014] A sixth feature, combinable with any of the following
features, wherein retrieving the signed first data digests from the
public blockchain includes identifying the signed first data
digests based on an identifier associated with the stored data item
and stored in the public blockchain.
[0015] The present 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 implementations
of the methods provided herein.
[0016] The present 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
implementations of the methods provided herein.
[0017] The described blockchain network can be used to verify the
integrity of the data stored in the blockchain network. It involves
a large number of nodes that can participate in the consensus
process, thereby ensuring the integrity of the data. In addition,
the described techniques provide an incentive mechanism based on
smart contracts to increase node participation in the public
sidechain.
[0018] It is appreciated that methods in accordance with the
present specification may include any combination of the aspects
and features described herein. That is, methods in accordance with
the present 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.
[0019] The details of one or more implementations of the present
specification are set forth in the accompanying drawings and the
description below. Other features and advantages of the present
specification will be apparent from the description and drawings,
and from the claims.
DESCRIPTION OF DRAWINGS
[0020] FIG. 1 depicts an example of an environment that can be used
to execute implementations of the present specification.
[0021] FIG. 2 depicts an example of a conceptual architecture in
accordance with implementations of the present specification.
[0022] FIG. 3 depicts an example of a system that can be used to
execute implementations of the present specification in accordance
with implementations of the present specification.
[0023] FIG. 4 depicts an example of a process of storing data in a
consortium blockchain network and an associated public sidechain
network according to aspects of the present specification.
[0024] FIG. 5 depicts an example of a process of retrieving data
from the consortium blockchain network, and verifying retrieved
data based on the public sidechain network according to aspects of
the present specification.
[0025] FIG. 6 depicts an example of a process that can be executed
in accordance with implementations of the present
specification.
[0026] FIG. 7 depicts an example of a diagram illustrating modules
of an apparatus in accordance with implementations of the
specification.
[0027] Like reference symbols in the various drawings indicate like
elements.
DETAILED DESCRIPTION
[0028] Implementations of the present specification include
computer-implemented methods for storing and retrieving
to-be-verified data associated with nodes of a blockchain network.
More particularly, implementations of the present specification are
directed to storing a data digest of the to-be-verified data
associated with one or more consortium blockchain network nodes
using a number of verification nodes, and retrieving the
to-be-verified data and the stored data digests.
[0029] To provide further context for implementations of the
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. The term blockchain is used herein to
generally refer to a DLS without reference to any particular use
case.
[0030] A blockchain is a data structure that stores transactions in
a way that the transactions are immutable, and can be subsequently
verified. 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.
[0031] Whereas a blockchain is a data structure for storing
transactions, a blockchain network is a network of computing nodes
that manage, update, and maintain one or more blockchains. As
introduced above, a blockchain network can be provided as a public
blockchain network, a private blockchain network, or a consortium
blockchain network.
[0032] In a public blockchain network, the consensus process is
controlled by nodes of the consensus network. For example,
hundreds, thousands, even millions of entities can cooperate a
public blockchain network, each of which operates at least one node
in the public blockchain network. Accordingly, the public
blockchain network can be considered a public network with respect
to the participating entities. In some examples, a majority of
entities (nodes) must sign every block in order for the block to be
valid, and added to the blockchain (distributed ledger) of the
blockchain network. Example public blockchain networks include
particular peer-to-peer payment networks that leverage a
distributed ledger, referred to as blockchain. As noted above, the
term blockchain, however, is used to generally refer to distributed
ledgers without particular reference to any particular blockchain
network.
[0033] In general, a public blockchain network supports public
transactions. A public transaction is shared with all of the nodes
within the public blockchain network, and are stored in a global
blockchain. A global blockchain is a blockchain that is replicated
across all nodes. That is, all 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 public blockchain network.
Examples of consensus protocols include, without limitation,
proof-of-work (POW), proof-of-stake (POS), and proof-of-authority
(POA). POW is referenced further herein as a non-limiting
example.
[0034] In general, a private blockchain network private blockchain
network is provided for a particular entity, which centrally
controls read and write permissions. The entity controls, which
nodes are able to participate in the blockchain network.
Consequently, private blockchain networks are generally referred to
as permissioned networks that place restrictions on who is allowed
to participate in the network, and on their level of participation
(e.g., only in certain transactions). Various types of access
control mechanisms can be used (e.g., existing participants vote on
adding new entities, a regulatory authority can control
admission).
[0035] 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, one
or more 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. Accordingly, the consortium blockchain network
can be considered a private network with respect to the
participating entities. In some examples, each entity (node) must
sign every block in order for the block to be valid, and added to
the blockchain. In some examples, at least a sub-set of entities
(nodes) (e.g., at least 7 entities) must sign every block in order
for the block to be valid, and added to the blockchain.
[0036] A blockchain is a tamper-proof, shared digital ledger that
records transactions in a public or private peer-to-peer network.
The ledger is distributed to all member nodes in the network, and
the history of asset transactions occurring in the network is
permanently recorded in the block. Prior to participating in a
transaction, a node on the blockchain may need to execute
computations using various techniques. Under current solutions,
because each blockchain is independent, a node of one blockchain
cannot communicate with other chains. For example, a node cannot
read data from other blockchains or exchange data with other
blockchains. In addition, even if a node does not need data from
other blockchains to execute a computation, performing such
computations entirely on a blockchain can consume a lot of time and
computational resources of the blockchain, if it requires
complicated computational logics and protocols.
[0037] Implementations of the specification are described in
further detail herein with reference to a consortium blockchain
network, which is public among the participating entities. It is
contemplated, however, that implementations of the specification
can be realized in any appropriate type of blockchain network.
[0038] Implementations of the specification are described in
further detail herein in view of the above context. More
particularly, and as introduced above, implementations of the
specification are directed to providing an off-chain smart contract
service capable of operating cross-chain data in a trusted
execution environment.
[0039] Specifically, the described techniques introduce a public
auxiliary blockchain (also referred to as a "sidechain") that is
used to verify the integrity of the data stored in the consortium
blockchain. Because the sidechain is public, a large number of
nodes can participate in the consensus process, thereby ensuring
the integrity of the data in the sidechain. A representation of
each transaction on the consortium blockchain is stored in the
sidechain. Thus, in order to alter the data in the consortium
blockchain, an attacker must also make a corresponding alteration
to the public sidechain. Making such an alteration in the public
sidechain will be much more difficult than in the consortium
blockchain, due to the number of nodes involved in the consensus
process for the public sidechain. In this way, the integrity of the
data in the consortium blockchain may be ensured. In addition, the
described techniques provide an incentive mechanism based on smart
contracts to increase node participation in the public sidechain. A
smart contract can be a computer agreement designed to disseminate,
verify, or enforce contracts in an informational manner. Smart
contracts allow trusted transactions to be performed without a
third-party involvement. These transactions are traceable and
irreversible.
[0040] The described techniques can have a variety of applications.
For example, during a copyright infringement litigation, the
plaintiff needs to provide the court with some type of digital
evidence to show the exact time she created the original work. If
the digital evidence submitted by the plaintiff is originally
stored at a consortium blockchain, it may not be able to meet the
required burden of proof, since the court cannot determine that the
digital evidence has not been tampered with. To establish an
evidentiary record that would be accepted by the court, the
plaintiff can store the data evidence using the described
techniques through an verification system. At the time of evidence
submission, the plaintiff can submit the digital evidence stored at
the consortium blockchain, along with copies of digital evidence
submitted by the verification nodes. This way, the court will be
more likely to recognize the authenticity of the digital evidence
because a large number of verification nodes are attesting to the
authenticity of the digital evidence.
[0041] Aside from the above-discussed example, the described
techniques can benefit many other applications that make use of the
blockchain technology.
[0042] FIG. 1 depicts an example of an environment 100 that can be
used to execute implementations of the specification. In some
examples, the environment 100 enables entities to participate in a
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 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 can each
computing device 106, 108 be a separate cloud computing system
including a number of computers interconnected by a network and
functioning as a distributed processing system.
[0043] In the depicted example, the computing systems 106, 108 can
each include any appropriate computing system that enables
participation as a node in the 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 systems 106, 108 hosts
one or more computer-implemented services for interacting with the
blockchain network 102. For example, the computing system 106 can
host computer-implemented services of a first entity (e.g.,
Participant A), such as transaction management system that the
first entity uses to manage its transactions with one or more other
entities (e.g., other participants). The computing system 108 can
host computer-implemented services of a second entity (e.g.,
Participant B), such as transaction management system that the
second entity uses to manage its transactions with one or more
other entities (e.g., other participants). In the example of FIG.
1, the blockchain network 102 is represented as a peer-to-peer
network of nodes, and the computing systems 106, 108 provide nodes
of the first entity, and second entity respectively, which
participate in the blockchain network 102.
[0044] FIG. 2 depicts an example of a conceptual architecture 200
in accordance with implementations of the specification. The
example of a 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 number 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.
[0045] 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).
[0046] 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 minder 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, 206 store
respective, complete copies 216', 216'', 216''' of the blockchain
216.
[0047] 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 transactions can include, without
limitation, exchanges of something of value (e.g., assets,
products, services, and currency). The transaction data is
immutably stored within the blockchain. That is, the transaction
data cannot be changed.
[0048] 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 examples of hash function includes, without limitation,
the secure hash algorithm (SHA)-256, which outputs 256-bit hash
values.
[0049] 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.
[0050] Blocks are added to the blockchain through a consensus
protocol. Multiple nodes within the blockchain network participate
in the consensus protocol, and compete to have a block added to the
blockchain. Such nodes are referred to as miners (or minder nodes).
POW, introduced above, is used as a non-limiting example.
[0051] The miner nodes execute the consensus process to add
transactions to the blockchain. Although multiple miner nodes
participate in the consensus process, only one miner node can write
the block to the blockchain. That is, the miner nodes compete in
the consensus process to have their block added to the blockchain.
In further detail, a miner node periodically collects pending
transactions from a transaction pool (e.g., up to a predefined
limit on the number of transactions that can be included in a
block, if any). The transaction pool includes transaction messages
from participants in the blockchain network. The miner node
constructs a block, and adds the transactions to the block. Before
adding the transactions to the block, the miner node checks whether
any of the transactions are already included in a block of the
blockchain. If a transaction is already included in another block,
the transaction is discarded.
[0052] The miner 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 miner also determines the hash
value of the most recent block in the blockchain (i.e., the last
block added to the blockchain). The miner node also adds a nonce
value, and a timestamp to the block header. In a mining process,
the miner node attempts to find a hash value that meets required
parameters. The miner node keeps changing the nonce value until
finding a hash value that meets the required parameters.
[0053] Every miner in the blockchain network attempts to find a
hash value that meets the required parameters, and, in this way,
compete with one another. Eventually, one of the miner nodes finds
a hash value that meets the required parameters, and advertises
this to all other miner nodes in the blockchain network. The other
miner nodes verify the hash value, and if determined to be correct,
verifies each transaction in the block, accepts the block, and
appends the block to their copy of the blockchain. In this manner,
a global state of the blockchain is consistent across all miner
nodes within the blockchain network. The above-described process is
the POW consensus protocol.
[0054] A non-limiting example is provided with reference to FIG. 2.
In this example, Participant A wants to send an amount of fund to
Participant B. Participant A generates a transaction message (e.g.,
including From, To, and Value fields), and sends the transaction
message to the blockchain network, which adds the transaction
message to a transaction pool. Each miner node in the blockchain
network creates a block, and takes all transactions from the
transaction pool (e.g., up to a predefined limit on the number of
transaction that can be added to a block, if any), and adds the
transactions to the block. In this manner the transaction published
by Participant A is added to the blocks of the miner nodes.
[0055] In some blockchain networks, cryptography is implemented to
maintain privacy of transactions. For example, if two nodes want to
keep a transaction private, such that other nodes in the blockchain
network cannot discern details of the transaction, the nodes can
encrypt the transaction data. Examples of cryptographic methods
include, without limitation, symmetric encryption, and asymmetric
encryption. Symmetric encryption refers to an encryption process
that uses a single key for both encryption (generating ciphertext
from plaintext), and decryption (generating plaintext from
ciphertext). In symmetric encryption, the same key is available to
multiple nodes, so each node can en-/de-crypt transaction data.
[0056] Asymmetric encryption uses keys pairs that each include a
private key, and a public key, the private key being known only to
a respective node, and the public key being known to any or all
other nodes in the blockchain network. A node can use the public
key of another node to encrypt data, and the encrypted data can be
decrypted using other node's private key. For example, and
referring again to FIG. 2, Participant A can use Participant B's
public key to encrypt data, and send the encrypted data to
Participant B. Participant B can use its private key to decrypt the
encrypted data (ciphertext) and extract the original data
(plaintext). Messages encrypted with a node's public key can only
be decrypted using the node's private key.
[0057] Asymmetric encryption is used to provide digital signatures,
which enables participants in a transaction to confirm other
participants in the transaction, as well as the validity of the
transaction. For example, a node can digitally sign a message, and
another node can confirm that the message was sent by the node
based on the digital signature of Participant A. Digital signatures
can also be used to ensure that messages are not tampered with in
transit. For example, and again referencing FIG. 2, Participant A
is to send a message to Participant B. Participant A generates a
hash of the message, and then, using its private key, encrypts the
hash to provide a digital signature as the encrypted hash.
Participant A appends the digital signature to the message, and
sends the message with digital signature to Participant B.
Participant B decrypts the digital signature using the public key
of Participant A, and extracts the hash. Participant B hashes the
message and compares the hashes. If the hashes are same,
Participant B can confirm that the message was indeed from
Participant A, and was not tampered with.
[0058] FIG. 3 depicts an example of a system 300 that can be used
to execute implementations of the present specification in
accordance with implementations of the present specification.
[0059] As illustrated in FIG. 3, the system 300 includes a
consortium blockchain network 302 including nodes 304a-304e
maintaining a consortium blockchain 306. The system 300 includes a
verification system 316, an incentive system 320, and a public
sidechain network 352. The public sidechain network 352 includes a
plurality of verification nodes 330, a public blockchain 356, and
public blockchain nodes (e.g., 354) maintaining the public
blockchain 356.
[0060] In operation, the consortium blockchain network 302 (i.e.,
the nodes 304a-e) receive requests to store data (360). The nodes
304a-e store the data in the consortium blockchain 306 according to
the mechanisms described above. The verification system 316
receives the stored data once it is added to the blockchain 306 (at
362). For example, the verification system can monitor the
consortium blockchain network 302 and determine that the data has
been stored once a consensus is reached by the nodes 304a-e on a
chain including the data.
[0061] In some implementations, the verification system 316 is
responsible for the interaction between the consortium blockchain
network 302 and the public sidechain network 352. In operation, the
verification system 316 (at 366) sends a data digest of the stored
data to verification nodes 330. In some implementations, the
verification nodes 330 are computing devices participating in the
public sidechain network 352. There may be a large number (e.g.,
thousands) of verification nodes 330. In some cases, the
verification system 316 may broadcast the data digest to the public
sidechain network 352. The verification nodes 330, upon receiving
the data digest, cryptographically sign the data digest using their
private key. Each verification node then attempts to store its
signed data digest in the public blockchain 356. In some
implementations, all signed data digests produced by the
verification nodes 330 are stored in the public blockchain 356. In
some cases, a certain number of the signed data digests are stored
in the public blockchain 356 and the others are discarded. This
number can be a function of the consensus mechanisms used in the
public sidechain network 352.
[0062] The system 300 may also include an incentive system 320. In
some implementations, the incentive system 320 may generate a smart
contract to be stored in the public blockchain 356. The smart
contract may be configured, when executed by the public sidechain
network, to provide a monetary reward to verification nodes 330
that participate in the verification of the stored data. For
example, a verification node 330 that successfully includes its
signed data digest in the public blockchain 356 may receive the
monetary reward automatically through execution of the smart
contract. In some cases, a verification node 330 that participates
in the verification of data requested from the consortium
blockchain (see FIG. 5, below) may receive the monetary reward
automatically through execution of the smart contract.
[0063] FIG. 4 depicts an example process 400 of storing data in a
consortium blockchain network and an associated public sidechain
network according to aspects of the present specification.
[0064] At 405, a data item is stored in the consortium blockchain
network 302. At 410, the verification system 316 receives the newly
stored data from the consortium blockchain network 302, such as by
communicating with nodes participating in the network. At 415, the
verification system 316 creates a data digest of the newly stored
data item. For example, the verification system 316 may create the
data digest by generating a hash of the stored data item using a
hashing algorithm, such as, for example, Secure Hash Algorithm 1
(SHA-1), SHA-256, Rivest-Shamir-Adleman (RSA), or other known
algorithms.
[0065] At 420, the verification system 316 requests verification of
the data digest by the verification nodes 330. In response, at 425,
the verification nodes 330 cryptographically sign the data digest
using their private keys. At 430, the verification nodes 330 store
their individual signed data digests in the public blockchain 356
managed by the public sidechain network 352. As described above, in
some implementations, only a certain number of the data digests
will be stored in the public blockchain 356 depending on the
consensus mechanisms employed by the public sidechain network
352.
[0066] FIG. 5 depicts an example process of retrieving data from
the consortium blockchain network 302, and verifying retrieved data
based on the public sidechain network 352. At 505, a request to
retrieve data is received by the consortium blockchain network 302
(i.e., by a node participating in the consortium blockchain
network). In some implementations, this request may be received by
the verification system 316.
[0067] At 510, the verification system 316 retrieves the requested
data from the consortium blockchain network 302, such as by
obtaining the requested data from a consensus version of the
consortium blockchain 306. At 515, the verification system 316
retrieves the signed data digests associated with the requested
data from the public sidechain network 352. In some cases, the
signed digests may be retrieved based on an identifier associated
with the stored data, such as a timestamp or other identifier
stored in the public blockchain 356 along with the signed data
digests by the verification nodes 330.
[0068] At 520, the verification system 316 requests signed data
digest of the retrieved data from the verification nodes 330. The
verification system 316 may create the data digest of the retrieved
data using the hashing algorithms described above. At 525, the
verification system 316 sends the data digests to the verification
nodes 330, so that verification nodes 330 can each
cryptographically sign the data digest of the retrieved data, and
at 530 return their signed version of the data digest to the
verification system 316.
[0069] At 535, the verification system 316 compares the signed data
digests of the retrieved data received from the verification nodes
330 to the signed data digests retrieved from the public blockchain
356 (which were created when the data was originally stored in the
consortium blockchain network, see FIG. 4). If the signed data
digests of the retrieved data received from the verification nodes
330 match the signed data digests retrieved from the public
blockchain 356, the stored data in the consortium blockchain
network 302 has not changed since it was originally stored
(540).
[0070] This process verifies that the requested data has not been
changed, because if it has not changed, the value of the signed
data digests of the retrieved data produced by the verification
nodes 330 will match the previously-stored data digests that were
created when the data was originally stored. If the data has
changed after being stored in the consortium blockchain, the signed
data digests of the retrieved data will not match those that were
stored in the public blockchain 356 when the data was originally
stored.
[0071] In some cases, the verification system 316 may only request
signed data digests at 520 from the verification nodes that
successfully inserted their signed data digests into the public
blockchain 356. For example, the verification nodes 330 can each
attempt to store a unique identifier (e.g., a public key)
identifying the particular node along with the data digest. Only
entries that are included in the consensus version of the public
blockchain 356 will thus be queried.
[0072] In some cases, the verification system 316 may only request
verification from a particular set of the verification nodes 330
when storing data to the consortium blockchain 306. In such a case,
the verification system 316 may only query the particular set of
nodes for signed data digests when verifying that retrieved data
from the consortium blockchain 306 has not changed.
[0073] FIG. 6 depicts an example of process 600 that can be
executed in accordance with implementations of the present
specification. In some implementations, the example of process 600
may be performed using one or more computer-executable programs
executed using one or more computing devices. For clarity of
presentation, the description that follows generally describes
process 600 in the context of the other figures in this
description. However, it will be understood that process 600 may be
performed, for example, by any suitable system, environment,
software, and hardware, or a combination of systems, environments,
software, and hardware, as appropriate. In some implementations,
various steps of process 600 can be run in parallel, in
combination, in loops, or in any order.
[0074] At 602, a data item is stored in a consortium blockchain
maintained by a consortium blockchain network.
[0075] At 604, a first data digest is generated based on the stored
data item.
[0076] At 606, the first data digest is sent to verification nodes,
so that each verification node cryptographically signs the first
data digest and stores its signed first data digest in a public
blockchain maintained by a public blockchain network. In some
implementations, the verification nodes are computing devices
participating in the public blockchain network. In some
implementations, each verification node is configured to
cryptographically sign the first data digest using a private key
associated with that verification node. In some implementations,
sending the first data digest to the verification nodes includes
broadcasting the first data digest to the public blockchain
network.
[0077] At 608, a request is received to retrieve the stored data
item.
[0078] At 610, in response to receiving the request, the requested
data item is retrieved from the consortium blockchain.
[0079] At 612, a second data digest is generated based on the
retrieved data item. In some implementations, generating the first
data digest includes calculating a hash of the stored data
item.
[0080] At 614, the second data digest is sent to the verification
nodes so that each verification node can cryptographically sign the
second data digests and return its signed second data digest.
[0081] At 616, the signed second data digests are received from the
verification nodes.
[0082] At 618, the signed first data digests are retrieved from the
public blockchain. In some implementations, retrieving the signed
first data digests from the public blockchain includes identifying
the signed first data digests based on an identifier associated
with the stored data item and stored in the public blockchain.
[0083] At 620, it is determined that the signed first data digests
match the signed second data digests.
[0084] At 622, in response to the determining, a response is sent
to retrieve the stored data item, the response indicating that the
stored data item has not changed since it was stored.
[0085] In some implementations, the process 600 further includes
storing a smart contract in the public blockchain, wherein the
smart contract is configured to provide a monetary reward to the
verification nodes in response to receiving the requested signed
second data digests from the verification nodes.
[0086] Referring to FIG. 7, FIG. 7 depicts an example of a diagram
illustrating modules of an apparatus 700 in accordance with
implementations of the specification. The apparatus 700 can be an
example implementation for storing and retrieving to-be-verified
data associated with nodes of a blockchain network. The apparatus
700 can correspond to the implementation shown in FIGS. 3-5, and
the apparatus 700 includes the following: a storage or storing unit
705, configured to store a data item in a consortium blockchain
maintained a consortium blockchain network; a first generator or
generating unit 710, configured to generate a first data digest
based on the stored data item; a first transmitter or transmitting
unit 715, configured to send the first data digest to verification
nodes, each verification node configured to cryptographically sign
its first data digest and store its signed first data digest in a
public blockchain maintained by the public blockchain network; a
receiver or a receiving unit 720, configured to receive a request
to retrieve the stored data item; a first retrieving unit 725,
configured to retrieve the requested data item from the consortium
blockchain in response to receiving the request; a second generator
or generating unit 730, configured to generate a second data digest
based on the retrieved data item; a requestor or requesting unit
735, configured to request assigned second data digests from the
verification nodes and in response to receiving the requested
signed second data digests from the verification nodes; a second
retrieving unit 740, configured to retrieve the signed first data
digests from the public blockchain; a determining unit 745,
configured to determine that the signed first data digests from the
public blockchain match the signed second data digests received
from the verification nodes; a second transmitter or transmitting
unit 750, configured to send a response to the request to retrieve
the stored data including the stored data item in response to the
determining, the response indicating that the stored data item has
not changed since it was stored.
[0087] In an optional implementation, the verification nodes are
computing devices participating in the public blockchain
network.
[0088] In an optional implementation, the apparatus 700 further
includes the following: a storage or storing sub-unit, configured
to store a smart contract in the public blockchain, wherein the
smart contract is configured to provide a monetary reward to the
verification nodes in response to receiving the requested signed
second data digests from the verification nodes.
[0089] In an optional implementation, the apparatus 700 further
includes the following: a calculator or a calculating sub-unit,
configured to calculate a hash of the stored data item.
[0090] In an optional implementation, each verification node is
configured to cryptographically sign the first data digest using a
private key associated with that verification node.
[0091] In an optional implementation, the apparatus 700 further
includes the following: a broadcasting sub-unit, configured to
broadcast the first data digest to the public blockchain
network.
[0092] In an optional implementation, the apparatus 700 further
includes the following: an identifier or an identifying sub-unit,
configured to identify the signed first data digests based on an
identifier associated with the stored data item and stored in the
public blockchain.
[0093] The system, apparatus, module, or unit illustrated in the
previous implementations 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 implementation 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.
[0094] For an implementation process of functions and roles of each
unit in the apparatus, references can be made to an implementation
process of corresponding steps in the previous method. Details are
omitted here for simplicity.
[0095] Because an apparatus implementation basically corresponds to
a method implementation, for related parts, references can be made
to related descriptions in the method implementation. The
previously described apparatus implementation is merely an example.
The units described as separate parts may or may not be physically
separate, and parts displayed as units may or may not be physical
units, may be located in one position, or may be distributed on a
number of network units. 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 implementations of the present
application without creative efforts.
[0096] FIG. 7 is a schematic diagram illustrating an internal
functional module and a structure of a consortium blockchain
network apparatus. 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.
[0097] The one or more processors are configured to store a data
item in a consortium blockchain maintained by a consortium
blockchain network; generate a first data digest based on the
stored data item; send the first data digest to verification nodes,
each verification node configured to cryptographically sign the
first data digest and store its signed first data digest in a
public blockchain maintained by a public blockchain network;
receive a request to retrieve the stored data item; in response to
receive the request, retrieve the requested data item from the
consortium blockchain; generate a second data digest based on the
retrieved data item; request signed second data digests from the
verification nodes and in response to receive the requested signed
second data digests from the nodes; retrieve the signed first data
digests from the public blockchain; determine that the signed first
data digests from the public blockchain match the signed second
data digests received from the verification nodes; and in response
to the determine, send a response to the request to retrieve the
stored data including the stored data item, the response indicating
that the stored data item has not changed since it was stored.
[0098] Optionally, the verification nodes are computing devices
participating in the public blockchain network.
[0099] Optionally, the one or more processors are configured to
store a smart contract in the public blockchain, wherein the smart
contract is configured to provide a monetary reward to the
verification nodes in response to receiving the requested signed
second data digests from the verification nodes.
[0100] Optionally, the one or more processors are configured to
calculate a hash of the stored data item.
[0101] Optionally, each verification node is configured to
cryptographically sign the first data digest using a private key
associated with that verification node.
[0102] Optionally, the one or more processors are configured to
broadcast the first data digest to the public blockchain
network.
[0103] Optionally, the one or more processors are configured to
identify the signed first data digests based on an identifier
associated with the stored data item and stored in the public
blockchain.
[0104] Implementations 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.
Implementations 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. The carrier may be a
tangible non-transitory computer storage medium. 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.
[0105] The term "data processing apparatus" encompasses all kinds
of apparatus, 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.
[0106] 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.
[0107] 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.
[0108] The processes and logic flows described in this
specification can be performed by one or more computers 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.
[0109] 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.
[0110] Generally, a computer will be coupled to at least one
non-transitory computer-readable storage medium (also referred to
as a computer-readable memory). The storage medium coupled to the
computer can be an internal component of the computer (e.g., an
integrated hard drive) or an external component (e.g., universal
serial bus (USB) hard drive or a storage system accessed over a
network). Examples of storage media can include, for example,
magnetic, magneto optical, or optical disks, solid state drives,
network storage resources such as cloud storage systems, or other
types of storage media. However, a computer need not have such
devices. 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.
[0111] To provide for interaction with a user, implementations 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'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.
[0112] 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.
[0113] While this specification contains many specific
implementation 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 implementations. Certain
features that are described in this specification in the context of
separate implementations can also be realized in combination in a
single implementation. Conversely, various features that are
described in the context of a single implementations can also be
realized in multiple implementations 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.
[0114] 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 implementations described above should not be
understood as requiring such separation in all implementations, 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.
[0115] Particular implementations of the subject matter have been
described. Other implementations 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.
* * * * *