Patent Publication Number: US-11025430-B2

Title: File provenance database system

Description:
TECHNICAL FIELD 
     This application generally relates to a database storage system, and more particularly, to a file provenance database system. 
     BACKGROUND 
     A centralized database stores and maintains data in one single database (e.g., database server) at one location. This location is often a central computer, for example, a desktop central processing unit (CPU), a server CPU, or a mainframe computer. Information stored on a centralized database is typically accessible from multiple different points. Multiple users or client workstations can work simultaneously on the centralized database, for example, based on a client/server configuration. A centralized database is easy to manage, maintain, and control, especially for purposes of security because of its single location. Within a centralized database, data redundancy is minimized as a single storing place of all data also implies that a given set of data only has one primary record. 
     However, a centralized database suffers from significant drawbacks. For example, a centralized database has a single point of failure. In particular, if there are no fault-tolerance considerations and a hardware failure occurs (for example a hardware, firmware, and/or a software failure), all data within the database is lost and work of all users is interrupted. In addition, centralized databases are highly dependent on network connectivity. As a result, the slower the connection, the amount of time needed for each database access is increased. Another drawback is the occurrence of bottlenecks when a centralized database experiences high traffic due to a single location. Furthermore, a centralized database provides limited access to data because only one copy of the data is maintained by the database. As a result, multiple devices cannot access the same piece of data at the same time without creating significant problems or risk overwriting stored data. Furthermore, because a database storage system has minimal to no data redundancy, data that is unexpectedly lost is very difficult to retrieve other than through manual operation from back-up storage. 
     Conventionally, a centralized database is limited by centralized control and approval, which makes such a system vulnerable to tampering and unauthorized file modifications. As such, what is needed is a solution to overcome these significant drawbacks. 
     SUMMARY 
     One example embodiment provides a system that includes a blockchain network, which includes a shared ledger, a file creation device, and a signature generation device. The file creation device is configured to create a source file. The signature generation device is configured to segment the source file into source file segments, create a number of auxiliary data segments that correspond to source file segments, perform a chameleon hash of the source file segments and the auxiliary data segments, obtain a source file signature from the chameleon hash, perform a cryptographic hash of the auxiliary data segments, obtain an auxiliary data signature from the cryptographic hash, and store the source file and cryptographic signatures to the shared ledger. Each auxiliary data segment includes a random string of data that corresponds to a source file segment. 
     Another example embodiment provides a method that includes one or more of creating a source file, segmenting the source file into source file segments, creating a number of auxiliary data segments corresponding to source file segments, performing a chameleon hash of the source file segments and the auxiliary data segments, obtaining a source file signature from the chameleon hash, performing a cryptographic hash of the auxiliary data segments, obtaining an auxiliary data signature from the cryptographic hash, and storing the source file and cryptographic signatures to a shared ledger of a blockchain network. Each auxiliary data segment includes a random string of data that is generated based on a corresponding source file segment. 
     A further example embodiment provides a non-transitory computer readable medium comprising instructions, that when read by a processor, cause the processor to perform one or more of creating a source file, segmenting the source file into source file segments, creating a number of auxiliary data segments corresponding to source file segments, performing a chameleon hash of the source file segments and the auxiliary data segments, obtaining a source file signature from the chameleon hash, performing a cryptographic hash of the auxiliary data segments, obtaining an auxiliary data signature from the cryptographic hash, and storing the source file and cryptographic signatures to a shared ledger of a blockchain network. Each auxiliary data segment includes a random string of data that is generated based on a corresponding source file segment. 
     One example embodiment provides a system that includes a blockchain network, a file redaction device, and a signature update device. The blockchain network includes a shared ledger. The file redaction device is configured to determine redacted segments of a source file. The signature update device is configured to receive the redacted source file segments, receive a stored trapdoor key and stored auxiliary data segments, determine modified auxiliary data from the redacted source file segments, the trapdoor key and the auxiliary data segments, execute chaincode to obtain a modified auxiliary data signature and identifiers of the redacted source file segments, and store the modified auxiliary data signature and identifiers of the redacted source file segments to the shared ledger. Each auxiliary data segment includes a random string of data that corresponds to a segment of the source file 
     Another example embodiment provides a method that includes one or more of determining, by a file redaction device, redacted segments of a source file, receiving, by a signature update device, the redacted source file segments, a stored trapdoor key, and stored auxiliary data segments, determining modified auxiliary data from the redacted source file segments, the trapdoor key and the auxiliary data segments, executing chaincode to obtain a modified auxiliary data signature and identifiers of the redacted source file segments, and storing the modified auxiliary data signature and identifiers of the redacted source file segments to a shared ledger of a blockchain network. Each stored auxiliary data segment including a random string of data corresponding to a segment of the source file. 
     A further example embodiment provides a non-transitory computer readable medium comprising instructions, that when read by a processor, cause the processor to perform one or more of determining, by a file redaction device, redacted segments of a source file, receiving, by a signature update device, the redacted source file segments, a stored trapdoor key, and stored auxiliary data segments, determining modified auxiliary data from the redacted source file segments, the trapdoor key and the auxiliary data segments, executing chaincode to obtain a modified auxiliary data signature and identifiers of the redacted source file segments, and storing the modified auxiliary data signature and identifiers of the redacted source file segments to a shared ledger of a blockchain network. Each stored auxiliary data segment including a random string of data corresponding to a segment of the source file. 
     One example embodiment provides a system that includes a blockchain network, including a shared ledger, and a file verification device. The file verification device is configured to initiate verification of a source file or a redacted source file, execute one of a smart contract or chaincode to verify the chameleon hash signature and the auxiliary data hash signature, and provide a notification whether the verification was successful or unsuccessful to a user who initiates verification. In response to the file verification device initiates verification of the source file, the file verification device is further configured to receive stored source file segments and stored auxiliary data segments, generate a chameleon hash signature from the stored source file segments and the stored auxiliary data segments, and generate an auxiliary data hash signature from the stored auxiliary data segments. In response to the file verification device initiates verification of the redacted source file, the file verification device further is configured to receive stored redacted file segments, stored auxiliary data segments, and stored modified auxiliary data, generate a chameleon hash signature from the stored redacted file segments and stored auxiliary data segments, and generate an auxiliary data hash signature from the stored modified auxiliary data. 
     Another example embodiment provides a method that includes one or more of initiating, by a file verification device, verification of a source file or a redacted source file, executing one of a smart contract or chaincode to verify the chameleon hash signature and the auxiliary data hash signature, and providing a notification whether the verification was successful or unsuccessful to a user initiating verification. In response to the file verification device initiating verification of the source file, the method further includes the file verification device receiving stored source file segments and stored auxiliary data segments, generating a chameleon hash signature from the stored source file segments and the stored auxiliary data segments, and generating an auxiliary data hash signature from the stored auxiliary data segments. In response to the file verification device initiating verification of the redacted source file, the method further includes the file verification device receiving stored redacted file segments, stored auxiliary data segments, and stored modified auxiliary data, generating a chameleon hash signature from the stored redacted file segments and stored auxiliary data segments, and generating an auxiliary data hash signature from the stored modified auxiliary data. 
     A further example embodiment provides a non-transitory computer readable medium comprising instructions, that when read by a processor, cause the processor to perform one or more of initiating, by a file verification device, verification of a source file or a redacted source file, executing one of a smart contract or chaincode to verify the chameleon hash signature and the auxiliary data hash signature, and providing a notification whether the verification was successful or unsuccessful to a user initiating verification. In response to the file verification device initiating verification of the source file, the method further includes the file verification device receiving stored source file segments and stored auxiliary data segments, generating a chameleon hash signature from the stored source file segments and the stored auxiliary data segments, and generating an auxiliary data hash signature from the stored auxiliary data segments. In response to the file verification device initiating verification of the redacted source file, the method further includes the file verification device receiving stored redacted file segments, stored auxiliary data segments, and stored modified auxiliary data, generating a chameleon hash signature from the stored redacted file segments and stored auxiliary data segments, and generating an auxiliary data hash signature from the stored modified auxiliary data. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  illustrates a logic network diagram of a system for securely storing source media files to a blockchain, according to example embodiments. 
         FIG. 1B  illustrates sanitizable signature generation for a file in a blockchain, according to example embodiments. 
         FIG. 1C  illustrates a logic network diagram of a system for securely redacting source media files to a blockchain, according to example embodiments. 
         FIG. 1D  illustrates sanitizable signature redaction for a file in a blockchain, according to example embodiments. 
         FIG. 1E  illustrates a logic network diagram of a system for securely verifying source media files from a blockchain, according to example embodiments 
         FIG. 2A  illustrates an example peer node configuration, according to example embodiments. 
         FIG. 2B  illustrates a further peer node configuration, according to example embodiments. 
         FIG. 3  illustrates a permissioned network, according to example embodiments. 
         FIG. 4A  illustrates a system messaging diagram for performing source file signature generation, according to example embodiments. 
         FIG. 4B  illustrates a system messaging diagram for performing source file signature redaction, according to example embodiments. 
         FIG. 4C  illustrates a system messaging diagram for performing signature verification, according to example embodiments. 
         FIG. 5A  illustrates a flow diagram of an example method of creating source file signatures in a blockchain, according to example embodiments. 
         FIG. 5B  illustrates a flow diagram of an example method of creating a redacted source file signature in a blockchain, according to example embodiments. 
         FIG. 5C  illustrates a flow diagram of an example method of verifying source and redacted file signatures in a blockchain. 
         FIG. 5D  illustrates a flow diagram of an example method of redacting a document associated with a blockchain transaction, according to example embodiments. 
         FIG. 6A  illustrates an example system configured to perform one or more operations described herein, according to example embodiments. 
         FIG. 6B  illustrates a further example system configured to perform one or more operations described herein, according to example embodiments. 
         FIG. 6C  illustrates a smart contract configuration among contracting parties and a mediating server configured to enforce the smart contract terms on the blockchain according to example embodiments. 
         FIG. 6D  illustrates an additional example system, according to example embodiments. 
         FIG. 7A  illustrates a process of new data being added to a database, according to example embodiments. 
         FIG. 7B  illustrates contents a data block including the new data, according to example embodiments. 
         FIG. 8  illustrates an example system that supports one or more of the example embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     It will be readily understood that the instant components, as generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of at least one of a method, apparatus, non-transitory computer readable medium and system, as represented in the attached figures, is not intended to limit the scope of the application as claimed but is merely representative of selected embodiments. 
     The instant features, structures, or characteristics as described throughout this specification may be combined in any suitable manner in one or more embodiments. For example, the usage of the phrases “example embodiments”, “some embodiments”, or other similar language, throughout this specification refers to the fact that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment. Thus, appearances of the phrases “example embodiments”, “in some embodiments”, “in other embodiments”, or other similar language, throughout this specification do not necessarily all refer to the same group of embodiments, and the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. 
     In addition, while the term “message” may have been used in the description of embodiments, the application may be applied to many types of network data, such as, packet, frame, datagram, etc. The term “message” also includes packet, frame, datagram, and any equivalents thereof. Furthermore, while certain types of messages and signaling may be depicted in exemplary embodiments they are not limited to a certain type of message, and the application is not limited to a certain type of signaling. 
     Example embodiments provide methods, systems, components, non-transitory computer readable media, devices, and/or networks, which provide a device-based blockchain system. 
     A decentralized database is a distributed storage system which includes multiple nodes that communicate with each other. A blockchain is an example of a decentralized database which includes an append-only immutable data structure resembling a distributed ledger capable of maintaining records between mutually untrusted parties. The untrusted parties are referred to herein as peers or peer nodes. Each peer maintains a copy of the database records and no single peer can modify the database records without a consensus being reached among the distributed peers. For example, the peers may execute a consensus protocol to validate blockchain storage transactions, group the storage transactions into blocks, and build a hash chain over the blocks. This process forms the ledger by ordering the storage transactions, as is necessary, for consistency. In a public or permission-less blockchain, anyone can participate without a specific identity. Public blockchains often involve native cryptocurrency and use consensus based on various protocols such as Proof of Work (PoW). On the other hand, a permissioned blockchain database provides a system which can secure inter-actions among a group of entities which share a common goal but which do not fully trust one another, such as businesses that exchange funds, goods, information, and the like. 
     A blockchain operates arbitrary, programmable logic, tailored to a decentralized storage scheme and referred to as “smart contracts” or “chaincodes.” In some cases, specialized chaincodes may exist for management functions and parameters which are referred to as system chaincode. Smart contracts are trusted distributed applications which leverage tamper-proof properties of the blockchain database and an underlying agreement between nodes which is referred to as an endorsement or endorsement policy. In general, blockchain transactions typically must be “endorsed” before being committed to the blockchain while transactions which are not endorsed are disregarded. A typical endorsement policy allows chaincode to specify endorsers for a transaction in the form of a set of peer nodes that are necessary for endorsement. When a client sends the transaction to the peers specified in the endorsement policy, the transaction is executed to validate the transaction. After validation, the transactions enter an ordering phase in which a consensus protocol is used to produce an ordered sequence of endorsed transactions grouped into blocks. 
     Nodes are the communication entities of the blockchain system. A “node” may perform a logical function in the sense that multiple nodes of different types can run on the same physical server. Nodes are grouped in trust domains and are associated with logical entities that control them in various ways. Nodes may include different types, such as a client or submitting-client node which submits a transaction-invocation to an endorser (e.g., peer), and broadcasts transaction-proposals to an ordering service (e.g., ordering node). Another type of node is a peer node which can receive client submitted transactions, commit the transactions and maintain a state and a copy of the ledger of blockchain transactions. Peers can also have the role of an endorser, although it is not a requirement. An ordering-service-node or orderer is a node running the communication service for all nodes, and which implements a delivery guarantee, such as a broadcast to each of the peer nodes in the system when committing transactions and modifying a world state of the blockchain. 
     A ledger is a sequenced, tamper-resistant record of all state transitions of a blockchain. State transitions may result from chaincode invocations (i.e., transactions) submitted by participating parties (e.g., client nodes, ordering nodes, endorser nodes, peer nodes, etc.). A transaction may result in a set of asset key-value pairs being committed to the ledger as one or more operands, such as creates, updates, deletes, and the like. The ledger includes a blockchain (also referred to as a chain) which is used to store an immutable, sequenced record in blocks. The ledger also includes a state database which maintains a current state of the blockchain. There is typically one ledger per channel. Each peer node maintains a copy of the ledger for each channel of which they are a member. 
     A chain is a transaction log which is structured as hash-linked blocks, and each block contains a sequence of N transactions where N is equal to or greater than one. The block header includes a hash of the block&#39;s transactions, as well as a hash of the prior block&#39;s header. In this way, all transactions on the ledger may be sequenced and cryptographically linked together. Accordingly, it is not possible to tamper with the ledger data without breaking the hash links. A hash of a most recently added blockchain block represents every transaction on the chain that has come before it, making it possible to ensure that all peer nodes are in a consistent and trusted state. The chain may be stored on a peer node file system (i.e., local, attached storage, cloud, etc.), efficiently supporting the append-only nature of the blockchain workload. 
     The current state of the immutable ledger represents the latest values for all keys that are included in the chain transaction log. Because the current state represents the latest key values known to a channel, it is sometimes referred to as a world state. Chaincode invocations execute transactions against the current state data of the ledger. To make these chaincode interactions efficient, the latest values of the keys may be stored in a state database. The state database may be simply an indexed view into the chain&#39;s transaction log, it can therefore be regenerated from the chain at any time. The state database may automatically be recovered (or generated if needed) upon peer node startup, and before transactions are accepted. 
     Some benefits of the instant solutions described and depicted herein include a new solution where a gap previously existed. Existing blockchain-based solutions for multimedia integrity verification do not allow modification of the content after the initial commitment. The present application describes a novel blockchain-based solution that supports advanced integrity requirements such as authorized multimedia content alteration (e.g., redaction of faces to protect the privacy of individuals) by its creator before the content is distributed, while preventing the end-users from reconstructing the redacted segments based on the published commitment. The proposed solution employs a chameleon hash function to generate the initial commitment, which is stored on the blockchain. The auxiliary data required for the integrity verification step is retained by the content creator and only a signature of this auxiliary data is stored on the blockchain. Any modifications to the multimedia content require only updating the signature of the auxiliary data, which is securely recorded on the blockchain. 
     Blockchain is different from a traditional database in that blockchain is not a central storage but rather a decentralized, immutable, and secure storage, where nodes must share in changes to records in the storage. Some properties that are inherent in blockchain and which help implement the blockchain include, but are not limited to, an immutable ledger, smart contracts, security, privacy, decentralization, consensus, endorsement, accessibility, and the like, which are further described herein. According to various aspects, the blockchain-based file integrity processes are implemented due to immutability/accountability, smart contracts/chaincodes, privacy/hidden aspects, decentralized/distributed organization, and consensus, —which are inherent and unique to blockchain. 
     In particular, with respect to immutability/accountability, the present application provides a solution that fundamentally relies on the fact that the commitments (content and auxiliary data signatures, i.e., the root nodes of the two Merkle trees, as well as timestamps, and content owner identity details) published on the blockchain are immutable/not changeable. 
     With respect to smart contracts/chaincodes, they are used to record/track both changes made to the content and to verify the integrity of the content. 
     With respect to privacy/hidden aspects, one of the core challenges solved by the present application are ways to make public commitment about a multimedia content/document and making selective redactions to the public commitment such that the actual content itself remains private/hidden during the recited process. 
     With respect to decentralized and distributed aspects, by using the decentralized/distributed nature of blockchain, the need for a single trusted entity to manage the published commitments is provided, which improves the integrity verification service. 
     With respect to consensus, distributed consensus ensures that no single entity in the blockchain network can modify the stored commitments on the blockchain in an unauthorized manner. 
     One of the benefits of the example embodiments is that it improves the functionality of a computing system by not relying on a centralized database. While it is possible to implement this application on a traditional database instead of a blockchain, such a scenario would require a centralized trusted entity who can guarantee the integrity of the commitments stored on the database and perform redaction on behalf of the content owners. In many applications, there is no single entity who can provide such a service and is fully trusted by all the players in the ecosystem. 
     Through the blockchain system described herein, a computing system can perform functionality without a single point of compromise because of the mechanisms inherent to blockchain. For example, all transactions and transaction results are stored in an immutable shared ledger by each major component that is a blockchain peer. Tampering is readily detectable as a shared ledger would not match other shared ledgers of the blockchain network. Instead of storing a regular cryptographic hash of the content on a database, the proposed application stores a redactable signature. This has two main advantages. Firstly, it becomes possible to make unauthorized modifications to the content without invalidating the stored commitment. Secondly, the stored commitment is no longer susceptible to brute-force hash inversion attacks, especially if the original content has low entropy or randomness. 
     The example embodiments provide numerous benefits over a traditional database. For example, through the blockchain the embodiments provide new technical means to address issues encountered in storage and verification of redacted files. Meanwhile, a traditional database could not be used to implement the example embodiments because traditional databases utilize centralized storage that may be tampered with and does not rely on all blockchain peers to reach consensus for new transactions. Accordingly, the example embodiments provide for a specific solution to a problem in the arts/field of secure document and file control. 
     The example embodiments also change how data may be stored within a block structure of the blockchain. For example, data and transactions that will be stored in the blockchain will be signatures (root nodes) of two Merkle trees, which constitute the redactable signatures of the content. Additionally, metadata about the content, including creator ID, device authentication details, timestamp of content creation, logs of authorized modifications, and user authentications may all be stored on the blockchain. 
     The present application achieves the key functional requirements of (i) guaranteeing content integrity while allowing for declared modifications to the content and (ii) content privacy. A dishonest creator may perform unauthorized (not recorded on the blockchain) modifications to the content after making the initial commitment, without being detected by the recipient. The content recipient cannot learn any information about the original data contained in the redacted segments during signature verification. 
     While significant advancements have been made in the field of multimedia forensics to detect altered content, existing techniques are mostly passive as they rarely enable the content creator to prove the integrity of the released content. In many application scenarios, the creator has a strong incentive to establish the provenance and integrity of the multimedia data created and released by him. Since blockchain technology provides an immutable distributed database, it is an ideal solution for reliably time-stamping content with its creation time and storing an irrefutable commitment of the content at the time of its creation. However, a blockchain-based approach does not allow modification of the content after the initial commitment. The present application describes a unique blockchain-based solution that supports advanced integrity requirements such as authorized multimedia content alteration (e.g., redaction of faces to protect the privacy of individuals) by its creator before the content is distributed, while preventing the end-users from reconstructing the redacted segments based on the published commitment. The proposed solution employs a chameleon hash function to generate the initial commitment, which is stored on the blockchain. The auxiliary data required for the integrity verification step is retained by the content creator and only a signature of this auxiliary data is stored on the blockchain. Any modifications to the multimedia content require only updating the signature of the auxiliary data, which is securely recorded on the blockchain. Thus, the proposed approach enables verification of integrity of redacted multimedia content without compromising the content privacy requirements. 
     In today&#39;s era of unreliable news, the easy availability of multimedia manipulation tools has made it difficult to trust what we see (image or video) or hear (audio). However, multimedia data (e.g., audio/video recordings) are admissible as evidence in courts and are often portrayed by the media as the ultimate “truth” of what happened. While significant advancements have been made in the field of multimedia forensics to detect altered content, these techniques are mostly passive because the content recipient attempts to verify the integrity of multimedia data without any inputs from the content creator. In many scenarios (e.g., citizen journalism, law enforcement), the content creator does have a strong incentive to establish the provenance and integrity of the multimedia data created and released by him. 
     Though active content authentication solutions such as watermarking and digital signatures have been proposed, they do not provide the creator of multimedia content with the ability to prove to a future recipient the following claims about the content: (i) ownership, (ii) device used to create the content, (iii) time of creation, and (iv) either the content has not been modified after creation or an immutable log of modifications made to the content after creation. These requirements can be met by enabling the content owner to make an irrefutable commitment about the multimedia content at the time of creation so that a the recipient can verify these details at a later point in time. 
     Blockchain is a peer-to-peer distributed ledger that immutably records a sequence of transactions without the need for any centralized or trusted entities. While blockchain has already been successfully applied in cryptocurrencies such as Bitcoin, the underlying technology can be used to create a tamper-proof audit trail in many applications. When combined with smart contracts o chaincodes, blockchain is a natural solution for storing the multimedia content creation record and immutably tracking all permissible changes after content creation. Note that commitments on the blockchain can be performed directly by the content creator or through a third-party service provider. While ownership of the content can be established through biometric authentication of the creator, the device itself can be authenticated through its unique fingerprint (e.g., photo response non-uniformity (PRNU) of a camera or microphone imperfections). Solutions are also available for trusted time-stamping of multimedia content using blockchain. Therefore, the present application focuses only the content authentication problem, and specifically on challenges in proving authenticity after revisions are made to the media after its creation. 
     The main limitation of blockchain-based approach is that the content creator is required to commit to a tamper-proof signature of the content at the time of its creation. Any further modifications to the content will surely invalidate this signature. In real-world use cases, the creator may have valid reasons to alter the content before distribution. For example, a bodycam video captured by law enforcement is used to prove innocence of the officer and a true description of the event. However, the privacy of the subjects in the video is important. Hence, the contents are sometimes redacted before they are released to the public. One would expect that the edited released video continues to faithfully depict the true event while protecting personally sensitive information of its subjects. Similar requirements are also felt in legal documents and scene-of-crime pictures. One possible solution is to employ redactable or sanitizable signature schemes to generate the initial commitment. The key limitation of such schemes is the need for a trusted third-party ‘censor’ or ‘sanitizer’, who performs the redaction on behalf of the content creator. Secondly, this approach also assumes a perfect communication protocol between the creator and the censor. Sanitizable signature schemes rely on this feature to prevent the creator from making undetectable modifications. Moreover, since the redacted segments may have a low entropy or randomness, the published commitment should not leak any information that enables the receiver to unwrap the redacted segments. 
     The present application describes a novel blockchain-based solution for multimedia integrity verification that overcomes all of the above-mentioned limitations. The primary contribution of this work is a sanitizable signature method that utilizes the properties of blockchain, chameleon hash functions, and Merkle trees to efficiently sign the given multimedia content, transparently update the signature upon content modification, and verify the integrity of the released content. We also present a theoretical analysis of the security properties and computational complexity of the proposed solution. 
       FIG. 1A  illustrates a logic network diagram of a system  100  for securely storing source media files to a blockchain, according to example embodiments. Referring to  FIG. 1A , the system  100  includes a file creator  108 , who is a user who creates or captures a source file  116  with a source device  112 . The source device  112  may be a computer of any type including a mobile computer, a desktop computer, a server, a smartphone, or a wearable computer. Such a computer  112  may or may not include a camera, a microphone, speakers, or a display. The source device  112  may additionally or alternately include a picture camera, a video camera, or an audio recorder. The source file  116  may contain any combination of text (as a document), video, audio, or graphics  114 . One or more of text, video, audio, or graphics  114  may not be present in the source file  116 . The source device  112  can make use of device authentication  144  and the authenticated source device  146  can be stored on the blockchain network  104 . 
     The present application makes use of biometric authentication  148  in order to ensure provenance of both the file creator  108 A and the source device  112  used to create or capture the source file  116 . Provenance, in the context of the present application, is the history of ownership back to the origin of the source file  116 . Biometric authentication  148  is used to create a blockchain transaction that stores an authenticated file creator and source device signature  150 A to a shared ledger of a blockchain network  104 . The blockchain network  104  may be either a public or a permissioned blockchain network  104 . The only difference lies in how the transaction is approved by the relevant stakeholders. In a permissioned blockchain this can be handled via smart contracts and endorsement policies. In a public blockchain, multi-signatures can be employed to obtain “pre-approval” before the miners commit the transaction to the blockchain. 
     Once the source file  116  has been created or captured by the file creator  108 A, the source file  116  is segmented by a segmentation function  120  into a plurality of source file segments  122 A. Various forms of existing software and software applications may be used to segment the source file  116 . In one embodiment, the source file segments  122 A are of equal size. In another embodiment, some source file segments  122 A are of a first size while other source file segments  122 A are of a different second size. In another embodiment, source file segments  122 A are of a variable size. The segmentation function  120  produces N source file segments  122 A, where N is the number of source file segments  122 A. 
     Following segmentation  120 , an auxiliary data generation function  124  generates N auxiliary data segments  125 . Therefore, the number N of auxiliary data segments  125  is equal to the number N of source file segments  122 A. Auxiliary data is a random string of data that is generated independent of the source file  116 . This random string of data is then segmented into the auxiliary data segments  125 . At this point, there are N source file segments  122 A and N auxiliary data segments  125 . Alternately, one may generate N random (shorter) strings individually. 
     The present application utilizes both a chameleon hashing function  128  and a cryptographic hash function  136  to process the source file segments  122 A and the auxiliary data segments  125 . Chameleon hash functions are randomized collision-resistant hash functions with the additional property that given a trapdoor, one can efficiently generate collisions. More specifically, each function in the family is associated with a pair of public and private (trapdoor) keys with the following properties (i) anyone who knows the public key can compute the associated hash function, (ii) for those who do not know the trapdoor the function is collision resistant in the usual sense, and (iii) the holder of the trapdoor information can easily find collisions for every input. A cryptographic hash function is a mathematical algorithm that maps data of arbitrary size to a bit string of a fixed size (a hash) and is designed to be a one-way function, that is, a function which is infeasible to invert. The only way to recreate the input data from an ideal cryptographic hash function&#39;s output is to attempt a brute-force search of possible inputs to see if they produce a match, or use a rainbow table of matched hashes. 
     The chameleon hashing function  128  converts source file segments  122 A (nodes M 1 , M 2 , M 3 , and M 4  of  FIG. 1B ) and auxiliary data segments  125  (nodes A 1 , A 2 , A 3 , and A 4  of  FIG. 1B ) as inputs into chameleon hash leaf nodes (nodes V 4 , V 5 , V 6 , and V 7  of  FIG. 1B ). 
     A chameleon hash is defined by the triplet: (Gen; CH; CH −1 ), where Gen is a key generation algorithm that generates a key pair (HK; TD), with HK being the hashing (public) key and TD being the trapdoor (secret) key  168  that is used for finding collisions. The public key HK defines a chameleon hash function CH HK (,), which on input a message m and a random string a (previously referred to as auxiliary data), generates a hash value CH HK (m, a) that satisfies the following properties.
         Collision Resistance: Given only CH HK (,), there is no efficient algorithm to find pairs (m1, a1) and (m2, a2) where (m1, a1) is not equal to (m2, a2) such that CH HK (m1, a1)=CH HK (m2, a2), except with negligible probability.   Trapdoor collisions: There is an efficient algorithm (CH −1 ) that on input the secret key TD, any pair (m1, a1) and any additional message m2, outputs a value a2 such that CH HK (m1, a1)=CH HK (m2, a2).   Uniformity: From seeing CH HK (m, a), where a is chosen uniformly at random, nothing is learned about the message m.       

     The cryptographic hash function  136  converts auxiliary data segments  125  (nodes A 1 , A 2 , A 3 , and A 4  of  FIG. 1B ) into cryptographic hash leaf nodes (nodes U 4 , U 5 , U 6 , and U 7  of  FIG. 1B ). 
     The Merkle Tree signature function  132  receives the chameleon hash leaf nodes (nodes V 4 , V 5 , V 6 , and V 7  of  FIG. 1B ) and generates leaf nodes V 2  and V 3  and root node V 1  as hashes. The Merkle Tree signature function  140  receives the cryptographic hash leaf nodes (nodes U 4 , U 5 , U 6 , and U 7  of  FIG. 1B ) and generates leaf nodes U 2  and U 3  and root node U 1  as hashes. Root node V 1  is a chameleon hash signature  134  and root node U 1  is an auxiliary data hash signature  142 . Both signatures  134 ,  140  are stored to the shared ledger of blockchain network  104  through blockchain transactions. At this point, the signatures corresponding to the source file  116  and authentication results for the file creator  108 A and source device  112  are stored to the immutable shared ledger. 
     System  100  is a sanitizable signature system that allows a file creator  108 A to sign the file or multimedia content at the time of its creation and record this initial signature on a blockchain. The blockchain should maintain an immutable log of the segments that were modified. At any given point in time (after content creation), a recipient who receives the content from the file creator  108 A should be able to verify the integrity of the received content, i.e., identify which segments have been modified and ensure that the remaining segments have not been altered by the file creator  108 A. 
       FIG. 1B  illustrates sanitizable signature generation  150  for a file in a blockchain, according to example embodiments. Referring to  FIG. 1B , the signatures  150  are based on a source file M. The source file M is divided into source file segments  122 A, identified as source file segments M 1 , M 2 , M 3 , and M 4 . There may be any number of source file segments  122 A in a source file  116 , although four such segments  122 A are shown in  FIG. 1B  for simplicity. 
     Associated with each of the source file segments  122 A is an auxiliary data segment  125 , identified as auxiliary data segments A 1 , A 2 , A 3 , and A 4 . A chameleon hash Merkle tree  152  is created from the source file segments  122 A and the auxiliary data segments  125 . In a binary Merkle tree, every leaf node is labeled with a cryptographic hash of the input data blocks and every non-leaf node is labelled with the cryptographic hash of the labels of its two child nodes. In the present application, the input data blocks are the chameleon hashes of the individual segments. 
     Leaf node V 4  is created from source file segment M 1  and auxiliary data segment A 1 . Leaf node V 5  is created from source file segment M 2  and auxiliary data segment A 2 . Leaf node V 6  is created from source file segment M 3  and auxiliary data segment A 3 . Leaf node V 7  is created from source file segment M 4  and auxiliary data segment A 4 . Leaf node V 2  is created from hashes of leaf nodes V 4  and V 5 . Leaf node V 3  is created from hashes of leaf nodes V 6  and V 7 . Finally, a root node V 1  is created from hashes of leaf nodes V 2  and V 3 . The root node V 1  is chameleon hash root node  134 , which is the signature that is stored to the shared ledger of the blockchain network  104  for the source file. 
     An auxiliary data Merkle tree  156  is created from the auxiliary data segments  125 . Leaf node U 4  is created from auxiliary data segment A 1 . Leaf node U 5  is created from auxiliary data segment A 2 . Leaf node U 6  is created from auxiliary data segment A 3 . Leaf node U 7  is created from auxiliary data segment A 4 . Leaf node U 2  is created from hashes of leaf nodes U 4  and U 5 . Leaf node U 3  is created from hashes of leaf nodes U 6  and U 7 . Finally, root node U 1  is created from hashes of leaf nodes U 2  and U 3 . The root node U 1  is auxiliary data root node  142 A, which is the signature that is stored to the shared ledger of the blockchain network  104  for the auxiliary data file. Both the content (i.e. corresponding to the source file  116 ) and auxiliary data signatures are broadcast to the blockchain nodes, which verify both the signatures before recording (U 1 , V 1 ) on the shared ledger, along with metadata about the content. 
       FIG. 1C  illustrates a logic network diagram of a system  160  for securely redacting source media files to a blockchain, according to example embodiments. Referring to  FIG. 1C , the system  160  includes a redacted file creator  108 B, who is a user who redacts or otherwise modifies the source file  116 . In one embodiment, the redacted file creator  108 B is a different individual than the file creator  108 A. In another embodiment, the redacted file creator  108 B is a same individual as the file creator  108 A. 
     The present application makes use of biometric authentication  148  in order to ensure provenance of the redacted file creator  108 B. Provenance, in the context of the present application, is the history of ownership back to the origin of the source file  116 . Biometric authentication  148  is used to create a blockchain transaction that stores an authenticated redacted file creator signature  150 B to the shared ledger of the blockchain network  104 . Once authenticated, the redacted file creator  108 B redacts/modifies a subset of segments in the content, and updates the initial signature on the blockchain. One critical requirement is content privacy, which implies that an adversary having access to the redacted content and logs available on the blockchain should not be able to reconstruct the original data that was redacted by the redacted file creator  108 B. 
     After the source file  116  has been created or captured by the file creator  108 A, the redacted file creator  108 B utilizes redaction software  164  to convert one or more source file segments  122 B into redacted file segments  122 B. 
     A collision finding function  172  uses the trapdoor key  168  to convert the redacted file segments  122 B and auxiliary data segments  125  into modified auxiliary data  174 . Finally, a smart contract or chaincode for auxiliary data signature update  176  converts the modified auxiliary data  174  into a modified auxiliary data signature and redacted segments identifiers (IDs)  178 . The modified auxiliary data signature and redacted segments identifiers (IDs)  178  is included in a blockchain transaction, which following conventional transaction endorsement is committed to the shared ledger. At this point, the blockchain includes authentications for the file creator  108 A, source device  112 , and redacted file creator  108 B as well as the (original) chameleon hash signature  134 , auxiliary data hash signature  142 , the modified auxiliary data signature  178 , and redacted segments IDs  178 . 
       FIG. 1D  illustrates sanitizable signature redaction  180  for a file in a blockchain, according to example embodiments. Referring to  FIG. 1D , the signatures  180  are based on a redacted source file M. The source file M is divided into redacted source file segments  122 B, identified as redacted source file segments M 1 , M 2 , M 3 ′, and M 4 . Redacted source file segment M 3 ′ represents a redacted source file segment. There may be any number of redacted source file segments  122 B in a redacted source file, although four such segments  122 B are shown in  FIG. 1D  for simplicity. 
     Associated with each of the redacted source file segments  122 B is auxiliary data segments  125 , identified as auxiliary data segments A 1 , A 2 , A 3 ′, and A 4 . Auxiliary data segment A 3 ′ is modified auxiliary data  174 . In the case of redaction, a new chameleon hash Merkle tree  152  and chameleon hash root node  134  are not created; all that is needed is a modified auxiliary data Merkle tree  182  and a modified auxiliary data hash root node  142 B. 
     The modified auxiliary data Merkle tree  182  is created from the auxiliary data segments  125 . And the modified auxiliary data  174 . Leaf node U 4  is created from auxiliary data segment A 1 . Leaf node U 5  is created from auxiliary data segment A 2 . Leaf node U 6 ′ is created from modified auxiliary data segment A 3 ′. Leaf node U 7  is created from auxiliary data segment A 4 . Leaf node U 2  is created from leaf nodes U 4  and U 5 . Leaf node U 3  is created from leaf nodes U 6 ′ and U 7 . Finally, root node U 1  is created from leaf nodes U 2  and U 3 . The root node U 1  is a modified auxiliary hash data root node  142 B, which is the signature that is stored to the shared ledger of the blockchain network  104  for the redacted data. Modified auxiliary hash data root node  142 B may be created from leaf nodes U 2 , U 6 ′, and U 7   184 , which are represented in  FIG. 1D  as underlines to denote their special use when constructing root node U 1 . 
       FIG. 1E  illustrates a logic network diagram of a system  185  for securely verifying source media files from a blockchain, according to example embodiments. Referring to  FIG. 1E , the system  185  includes a file verifier  108 C, who is a user who verifies either the source file  116  or the redacted source file. In one embodiment, the file verifier  108 C is a different individual than the file creator  108 A or redacted file creator  108 B. In another embodiment, file verifier  108 C is a same individual as one or both of the file creator  108 A or the redacted file creator  108 B. 
     The present application makes use of biometric authentication  148  in order to ensure provenance of principally the file creator  108 A, and optionally the file verifier  108 C to track the recipients of the file. It is important for the file verifier  108 C to verify the identity of the sender (i.e. a request for biometric identification of the file creator  108 A) to ensure the file was indeed created by the sender. Biometric authentication  148  is used to create a blockchain transaction that stores an authenticated file verifier signature  150 C to the shared ledger of the blockchain network  104 . 
     Depending on whether the source file  116  or redacted source file is being verified, the input to the chameleon hash function  128  may differ. If the source file  116  is being verified, the inputs to the chameleon hashing function  128  are the source file segments  122 A and the auxiliary data segments  125 . If the redacted source file is being verified, the inputs to the chameleon hashing function  128  are the redacted file segments  122 B and the modified auxiliary data  174 . Similarly, if the source file  116  is being verified, the input to the cryptographic hashing function  136  is the auxiliary data segments  125 . If the redacted source file is being verified, the input to the cryptographic hashing function  136  is the modified auxiliary data  174 . 
     The Merkle tree signature function  132  produces a chameleon hash signature  132  to a smart contract for verification  190 , and the Merkle tree signature function  140  produces an auxiliary data hash signature  142  to the smart contract for verification  190 . The smart contract for verification, after receiving the chameleon hash signature  134  and the auxiliary data hash signature  142 , retrieves the stored signatures from the shared ledger and compares the newly calculated chameleon hash signature  134  and the auxiliary data hash signature  142  to the stored signatures. 
     If the signatures match, then the integrity of the source file  116  or redacted source file has been verified, and the smart contract for verification  190  provides a verification successful notification  192  and an identifier for the redacted segments  194  (if a redacted file is being verified). If the signatures do not match, this may be an indication of tampering or other form of fraud detection and typically an appropriate notification would be provided to the file verifier  108 C and/or a system administrator. 
       FIG. 2A  illustrates a blockchain architecture configuration  200 , according to example embodiments. Referring to  FIG. 2A , the blockchain architecture  200  may include certain blockchain elements, for example, a group of blockchain nodes  202 . The blockchain nodes  202  may include one or more nodes  204 - 210  (these four nodes are depicted by example only). These nodes participate in a number of activities, such as blockchain transaction addition and validation process (consensus). One or more of the blockchain nodes  204 - 210  may endorse transactions based on endorsement policy and may provide an ordering service for all blockchain nodes in the architecture  200 . A blockchain node may initiate a blockchain authentication and seek to write to a blockchain immutable ledger stored in blockchain layer  216 , a copy of which may also be stored on the underpinning physical infrastructure  214 . The blockchain configuration may include one or more applications  224  which are linked to application programming interfaces (APIs)  222  to access and execute stored program/application code  220  (e.g., chaincode, smart contracts, etc.) which can be created according to a customized configuration sought by participants and can maintain their own state, control their own assets, and receive external information. This can be deployed as a transaction and installed, via appending to the distributed ledger, on all blockchain nodes  204 - 210 . 
     The blockchain base or platform  212  may include various layers of blockchain data, services (e.g., cryptographic trust services, virtual execution environment, etc.), and underpinning physical computer infrastructure that may be used to receive and store new transactions and provide access to auditors which are seeking to access data entries. The blockchain layer  216  may expose an interface that provides access to the virtual execution environment necessary to process the program code and engage the physical infrastructure  214 . Cryptographic trust services  218  may be used to verify transactions such as asset exchange transactions and keep information private. 
     The blockchain architecture configuration of  FIG. 2A  may process and execute program/application code  220  via one or more interfaces exposed, and services provided, by blockchain platform  212 . The code  220  may control blockchain assets. For example, the code  220  can store and transfer data, and may be executed by nodes  204 - 210  in the form of a smart contract and associated chaincode with conditions or other code elements subject to its execution. As a non-limiting example, smart contracts may be created to execute reminders, updates, and/or other notifications subject to the changes, updates, etc. The smart contracts can themselves be used to identify rules associated with authorization and access requirements and usage of the ledger. For example, the information  226  may include various verification request transactions. Verification request transactions  226  may be processed by one or more processing entities (e.g., virtual machines) included in the blockchain layer  216 . The result  228  may include a source file and data signatures. The physical infrastructure  214  may be utilized to retrieve any of the data or information described herein. 
     Within chaincode, a smart contract may be created via a high-level application and programming language, and then written to a block in the blockchain. The smart contract may include executable code which is registered, stored, and/or replicated with a blockchain (e.g., distributed network of blockchain peers). A transaction is an execution of the smart contract code which can be performed in response to conditions associated with the smart contract being satisfied. The executing of the smart contract may trigger a trusted modification(s) to a state of a digital blockchain ledger. The modification(s) to the blockchain ledger caused by the smart contract execution may be automatically replicated throughout the distributed network of blockchain peers through one or more consensus protocols. 
     The smart contract may write data to the blockchain in the format of key-value pairs. Furthermore, the smart contract code can read the values stored in a blockchain and use them in application operations. The smart contract code can write the output of various logic operations into the blockchain. The code may be used to create a temporary data structure in a virtual machine or other computing platform. Data written to the blockchain can be public and/or can be encrypted and maintained as private. The temporary data that is used/generated by the smart contract is held in memory by the supplied execution environment, then deleted once the data needed for the blockchain is identified. 
     A chaincode may include the code interpretation of a smart contract, with additional features. As described herein, the chaincode may be program code deployed on a computing network, where it is executed and validated by chain validators together during a consensus process. The chaincode receives a hash and retrieves from the blockchain a hash associated with the data template created by use of a previously stored feature extractor. If the hashes of the hash identifier and the hash created from the stored identifier template data match, then the chaincode sends an authorization key to the requested service. The chaincode may write to the blockchain data associated with the cryptographic details. In  FIG. 2A , a blockchain platform  212  may receive a blockchain transaction  226  to verify the integrity of a file stored on the blockchain. One function may be to request source file and auxiliary data signatures  228 , which may be provided to one or more of the nodes  204 - 210 . 
       FIG. 2B  illustrates an example of a transactional flow  250  between nodes of the blockchain in accordance with an example embodiment. Referring to  FIG. 2B , the transaction flow may include a transaction proposal  291  sent by an application client node  260  to an endorsing peer node  281 . The endorsing peer  281  may verify the client signature and execute a chaincode function to initiate the transaction. The output may include the chaincode results, a set of key/value versions that were read in the chaincode (read set), and the set of keys/values that were written in chaincode (write set). The proposal response  292  is sent back to the client  260  along with an endorsement signature, if approved. The client  260  assembles the endorsements into a transaction payload  293  and broadcasts it to an ordering service node  284 . The ordering service node  284  then delivers ordered transactions as blocks to all peers  281 - 283  on a channel. Before committal to the blockchain, each peer  281 - 283  may validate the transaction. For example, the peers may check the endorsement policy to ensure that the correct allotment of the specified peers have signed the results and authenticated the signatures against the transaction payload  293 . 
     Referring again to  FIG. 2B , the client node  260  initiates the transaction  291  by constructing and sending a request to the peer node  281 , which is an endorser. The client  260  may include an application leveraging a supported software development kit (SDK), such as NODE, JAVA, PYTHON, and the like, which utilizes an available API to generate a transaction proposal. The proposal is a request to invoke a chaincode function so that data can be read and/or written to the ledger (i.e., write new key value pairs for the assets). The SDK may serve as a shim to package the transaction proposal into a properly architected format (e.g., protocol buffer over a remote procedure call (RPC)) and take the client&#39;s cryptographic credentials to produce a unique signature for the transaction proposal. 
     In response, the endorsing peer node  281  may verify (a) that the transaction proposal is well formed, (b) the transaction has not been submitted already in the past (replay-attack protection), (c) the signature is valid, and (d) that the submitter (client  260 , in the example) is properly authorized to perform the proposed operation on that channel. The endorsing peer node  281  may take the transaction proposal inputs as arguments to the invoked chaincode function. The chaincode is then executed against a current state database to produce transaction results including a response value, read set, and write set. However, no updates are made to the ledger at this point. In  292 , the set of values, along with the endorsing peer node&#39;s  281  signature is passed back as a proposal response  292  to the SDK of the client  260  which parses the payload for the application to consume. 
     In response, the application of the client  260  inspects/verifies the endorsing peers signatures and compares the proposal responses to determine if the proposal response is the same. If the chaincode only queried the ledger, the application would inspect the query response and would typically not submit the transaction to the ordering node service  284 . If the client application intends to submit the transaction to the ordering node service  284  to update the ledger, the application determines if the specified endorsement policy has been fulfilled before submitting (i.e., did all peer nodes necessary for the transaction endorse the transaction). Here, the client may include only one of multiple parties to the transaction. In this case, each client may have their own endorsing node, and each endorsing node will need to endorse the transaction. The architecture is such that even if an application selects not to inspect responses or otherwise forwards an unendorsed transaction, the endorsement policy will still be enforced by peers and upheld at the commit validation phase. 
     After successful inspection, in step  293  the client  260  assembles endorsements into a transaction and broadcasts the transaction proposal and response within a transaction message to the ordering node  284 . The transaction may contain the read/write sets, the endorsing peers signatures and a channel ID. The ordering node  284  does not need to inspect the entire content of a transaction in order to perform its operation, instead the ordering node  284  may simply receive transactions from all channels in the network, order them chronologically by channel, and create blocks of transactions per channel. 
     The blocks of the transaction are delivered from the ordering node  284  to all peer nodes  281 - 283  on the channel. The transactions  294  within the block are validated to ensure any endorsement policy is fulfilled and to ensure that there have been no changes to ledger state for read set variables since the read set was generated by the transaction execution. Transactions in the block are tagged as being valid or invalid. Furthermore, in step  295  each peer node  281 - 283  appends the block to the channel&#39;s chain, and for each valid transaction the write sets are committed to current state database. An event is emitted, to notify the client application that the transaction (invocation) has been immutably appended to the chain, as well as to notify whether the transaction was validated or invalidated. 
       FIG. 3  illustrates an example of a permissioned blockchain network  300 , which features a distributed, decentralized peer-to-peer architecture, and a certificate authority  318  managing user roles and permissions. In this example, the blockchain user  302  may submit a transaction to the permissioned blockchain network  310 . In this example, the transaction can be a deploy, invoke, or query, and may be issued through a client-side application leveraging an SDK, directly through a REST API, or the like. Trusted business networks may provide access to regulator systems  314 , such as auditors (the Securities and Exchange Commission in a U.S. equities market, for example). Meanwhile, a blockchain network operator system of nodes  308  manage member permissions, such as enrolling the regulator system  314  as an “auditor” and the blockchain user  302  as a “client”. An auditor could be restricted only to querying the ledger whereas a client could be authorized to deploy, invoke, and query certain types of chaincode. 
     A blockchain developer system  316  writes chaincode and client-side applications. The blockchain developer system  316  can deploy chaincode directly to the network through a REST interface. To include credentials from a traditional data source  330  in chaincode, the developer system  316  could use an out-of-band connection to access the data. In this example, the blockchain user  302  connects to the network through a peer node  312 . Before proceeding with any transactions, the peer node  312  retrieves the user&#39;s enrollment and transaction certificates from the certificate authority  318 . In some cases, blockchain users must possess these digital certificates in order to transact on the permissioned blockchain network  310 . Meanwhile, a user attempting to drive chaincode may be required to verify their credentials on the traditional data source  330 . To confirm the user&#39;s authorization, chaincode can use an out-of-band connection to this data through a traditional processing platform  320 . 
       FIG. 4A  illustrates a system messaging diagram for performing source file signature generation  400 , according to example embodiments. Referring to  FIG. 4A , the system messaging diagram  400  includes a file creator  410 , a signature generation function  420 , and a blockchain network  430 . The file creator  410  has responsibility for creating or capturing a source file  116 , as explained with reference to  FIGS. 1A and 1B . 
     The file creator  410  creates or captures a source file  412  with a source device  112 . The file creator  410  then biometrically authenticates  414 A his/her identity and the identity of the source device  112 , and submits a file creator and source device authentication transaction  416  to the blockchain network  430 . In response, the blockchain network  430  endorses the transaction  422 A and stores the authentications to the shared ledger  424  of the blockchain network  430 . 
     The file creator  410  next submits the source file  418  to the signature generation function  420 . The signature generation function  420  in response segments the source file  426  as previously described with reference to  FIGS. 1A and 1B , and performs a chameleon hash  428  and cryptographic hash on the source file segments and auxiliary data segments, and processes Merkle trees  432 . Processing the Merkle trees  432  produces a source file signature and an auxiliary data signature, which are included as a blockchain transaction  434  to the blockchain network  430 . In response, the blockchain network  430  endorses the transaction  422 B and stores both signatures to the shared ledger  436  of the blockchain network  430 . 
     The signature generation function  420  then transfers the auxiliary data  438  and a trapdoor key (used for the chameleon hash  428 ) back to the file creator  410 , who stores both  442 . At this point, both the source file and auxiliary data signatures as well as file creator and source device authentications are stored to a shared ledger of the blockchain network  430 , and the file creator  410  stores the original source file, auxiliary data  438 , and the trapdoor key  440 . 
       FIG. 4B  illustrates a system messaging diagram for performing source file signature redaction  445 , according to example embodiments. Referring to  FIG. 4B , the system messaging diagram  445  includes a redacted file creator  450 , a signature update function  452 , and a blockchain network  430 . 
     The redacted file creator  450  determines redacted source file segments  454  by redacting or modifying the source file. The redacted file creator  450  then biometrically authenticates  414 B his/her identity and submits a redacted file creator authentication transaction  456  to the blockchain network  430 . In response, the blockchain network  430  endorses the transaction  422 C and stores the authentications to the shared ledger  458  of the blockchain network  430 . 
     The redacted file creator  450  next submits redacted source file segments  460  to the signature update function  452 , along with the stored auxiliary data  438  and the trapdoor key  440 . The signature update function  452  in response generates modified auxiliary data  462  as previously described with reference to  FIGS. 1C and 1D . The signature update function  452  produces modified auxiliary data  462 , and computes a modified auxiliary data signature  463 , and provides a modified auxiliary data signature blockchain transaction  464  to the blockchain network  430 . In response, the blockchain network  430  endorses the transaction  422 D and stores modified segments identification  466  and a modified auxiliary data signature  468  to the shared ledger of the blockchain network  430 . 
       FIG. 4C  illustrates a system messaging diagram for performing signature verification  470 , according to example embodiments. Referring to  FIG. 4C , the system messaging diagram  470  includes a file verifier  472 , a signature verification function  474 , and a blockchain network  430 . 
     The file verifier  472  verifies the integrity of a source file signature or a redacted file signature previously stored to the blockchain network  430 . The file verifier  472  receives source file, redacted file, and auxiliary file  476 . The file verifier  472  biometrically authenticates  414 C his/her identity, and submits a file verifier authentication transaction  478  to the blockchain network  430 . In response, the blockchain network  430  endorses the transaction  422 E and stores the authentications to the shared ledger  480  of the blockchain network  430 . 
     The file verifier  472  next submits the source file or redacted file segments  482  and auxiliary data or modified auxiliary data  484  to the signature verification function  474 . The signature verification function  474  in response performs a chameleon hash  428  on the source file segments or redacted file segments  482  and auxiliary data or modified auxiliary data  484 , performs a cryptographic hash on the auxiliary data or modified auxiliary data  484 , and processes Merkle trees  432 . Processing the Merkle trees  432  produces a source file signature and an auxiliary data signature, which are included in a verify signatures  488  blockchain transaction  486  to the blockchain network  430 . In response, the blockchain network  430  endorses the transaction  422 F and a smart contract or chaincode of the blockchain network  430  verifies the signatures in the transaction  486  with the stored signatures on the blockchain. 
     If the signatures match, the blockchain network  430  provides a signatures verified notification  490  to the file verifier  472 . 
       FIG. 5A  illustrates a flow diagram  500  of an example method of creating source file signatures in a blockchain, according to example embodiments. Referring to  FIG. 5A , the method  500  may include one or more of the following steps. 
     At block  502 , a file creator  410  creates a source file with a source device. The source file may include text, video, audio, and/or graphics. 
     At block  504 , the file creator  410  and source device are biometrically authenticated, and the authentications are stored to a blockchain. 
     At block  506 , the source file is segmented into any number of segments. 
     At block  508 , auxiliary data is created that corresponds to the source file segments. 
     At block  510 , a chameleon hash is created from the source file segments and the auxiliary data. 
     At block  512 , a cryptographic hash is created from the auxiliary data. 
     At block  514 , signatures resulting from the chameleon hash and the cryptographic hash are stored to a shared ledger of the blockchain. 
       FIG. 5B  illustrates a flow diagram  520  of an example method of creating a redacted source file signature in a blockchain, according to example embodiments. Referring to  FIG. 5B , the method  520  may include one or more of the following steps. 
     At block  522 , a redacted file creator  450  creates a redacted source file, which removes or modifies one or more portions of the source file. The redacted source file may include text, video, audio, and/or graphics. 
     At block  524 , the redacted file creator  450  is biometrically authenticated, and the authentications are stored to the blockchain. 
     At block  526 , modified auxiliary data based on the redacted source file is generated. 
     At block  528 , a modified auxiliary data signature is computed that corresponds to the modified auxiliary data. 
     At block  530 , the modified auxiliary data signature is stored to a shared ledger of the blockchain. 
       FIG. 5C  illustrates a flow diagram  540  of an example method of verifying source and redacted file signatures in a blockchain, according to example embodiments. Referring to  FIG. 5C , the method  540  may include one or more of the following steps. 
     At block  542 , a file verifier  472  receives a source file, redacted segments of the source file, and auxiliary data. The source file and redacted source file may include text, video, audio, and/or graphics. 
     At block  544 , the file verifier  472  are biometrically authenticated, and the authentications are stored to the blockchain. 
     At block  546 , a chameleon hash is created from either the source file segments or redacted file segments, and the auxiliary data. 
     At block  548 , the file verifier  472  retrieves stored signatures for the source file or redacted source file and compares the retrieved signatures to the calculated source file hash or redacted source file hash. 
     At block  550 , the file verifier  472  is notified if the stored signatures match the calculated signatures (hashes). 
       FIG. 5D  illustrates a flow diagram  560  of an example method of redacting a document associated with a blockchain transaction, according to example embodiments. Referring to  FIG. 5B , the method  560  may include one or more of the following steps. 
     At block  562 , the method may also include identifying a blockchain transaction. The transaction may include content to be redacted. When redacting a transaction, the data that was originally identified in the transaction may be hidden or blocked from view in the actual committed blockchain transaction. For example, once a transaction is identified as requiring redaction, the transaction may still exist in a block to preserve immutability of that transaction, however, the transaction may be otherwise inaccessible and cannot be accessed or viewed by users. For example, one approach may include placing a contract in a genesis block of the blockchain with code indicating to record redacted transactions. Additionally, by sending a new transaction to the redaction contract identifying a particular blockchain transaction to be redacted, the new transaction may be recorded and a redaction procedure may identify the “improper transaction” as the transaction to be redacted on the blockchain. 
     At block  564 , the method includes pre-processing the blockchain transaction to identify whether content of the blockchain transaction is approved by one or more devices on a peer network associated with the blockchain. 
     At block  566 , the method includes approving content by one or more devices. If a transaction contains unexpected content, the pre-processing will identify this content and it will not be finalized or stored in the blockchain. As such, miner devices have their own filter for approving content (or not) and a consensus may be reached regarding the acceptance of content of a transaction. 
     At block  568 , the method includes processing the identified content by the one or more devices, in response to approving the content by the one or more devices. 
     At block  570 , the method includes storing the blockchain transaction on the blockchain. In this example, a pre-processing operation confirms the content of the transaction is recognizable or expected by potential miner devices on the peer network prior to committing a transaction that should not be permitted. 
       FIG. 6A  illustrates an example system  600  that includes a physical infrastructure  610  configured to perform various operations according to example embodiments. Referring to  FIG. 6A , the physical infrastructure  610  includes a module  612  and a module  614 . The module  614  includes a blockchain  620  and a smart contract  630  (which may reside on the blockchain  620 ), that may execute any of the operational steps  608  (in module  612 ) included in any of the example embodiments. The steps/operations  608  may include one or more of the embodiments described or depicted and may represent output or written information that is written or read from one or more smart contracts  630  and/or blockchains  620 . The physical infrastructure  610 , the module  612 , and the module  614  may include one or more computers, servers, processors, memories, and/or wireless communication devices. Further, the module  612  and the module  614  may be a same module. 
       FIG. 6B  illustrates an example system  640  configured to perform various operations according to example embodiments. Referring to  FIG. 6B , the system  640  includes a module  612  and a module  614 . The module  614  includes a blockchain  620  and a smart contract  630  (which may reside on the blockchain  620 ), that may execute any of the operational steps  608  (in module  612 ) included in any of the example embodiments. The steps/operations  608  may include one or more of the embodiments described or depicted and may represent output or written information that is written or read from one or more smart contracts  630  and/or blockchains  620 . The physical infrastructure  610 , the module  612 , and the module  614  may include one or more computers, servers, processors, memories, and/or wireless communication devices. Further, the module  612  and the module  614  may be a same module. 
       FIG. 6C  illustrates an example smart contract configuration among contracting parties and a mediating server configured to enforce the smart contract terms on the blockchain according to example embodiments. Referring to  FIG. 6C , the configuration  650  may represent a communication session, an asset transfer session or a process or procedure that is driven by a smart contract  630  which explicitly identifies one or more user devices  652  and/or  656 . The execution, operations and results of the smart contract execution may be managed by a server  654 . Content of the smart contract  630  may require digital signatures by one or more of the entities  652  and  656  which are parties to the smart contract transaction. The results of the smart contract execution may be written to a blockchain  620  as a blockchain transaction. The smart contract  630  resides on the blockchain  620  which may reside on one or more computers, servers, processors, memories, and/or wireless communication devices. 
       FIG. 6D  illustrates a system  660  including a blockchain, according to example embodiments. Referring to the example of  FIG. 6D , an application programming interface (API) gateway  662  provides a common interface for accessing blockchain logic (e.g., smart contract  630  or other chaincode) and data (e.g., distributed ledger, etc.). In this example, the API gateway  662  is a common interface for performing transactions (invoke, queries, etc.) on the blockchain by connecting one or more entities  652  and  656  to a blockchain peer (i.e., server  654 ). Here, the server  654  is a blockchain network peer component that holds a copy of the world state and a distributed ledger allowing clients  652  and  656  to query data on the world state as well as submit transactions into the blockchain network where, depending on the smart contract  630  and endorsement policy, endorsing peers will run the smart contracts  630 . 
     The above embodiments may be implemented in hardware, in a computer program executed by a processor, in firmware, or in a combination of the above. A computer program may be embodied on a computer readable medium, such as a storage medium. For example, a computer program may reside in random access memory (“RAM”), flash memory, read-only memory (“ROM”), erasable programmable read-only memory (“EPROM”), electrically erasable programmable read-only memory (“EEPROM”), registers, hard disk, a removable disk, a compact disk read-only memory (“CD-ROM”), or any other form of storage medium known in the art. 
     An exemplary storage medium may be coupled to the processor such that the processor may read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an application specific integrated circuit (“ASIC”). In the alternative, the processor and the storage medium may reside as discrete components. 
       FIG. 7A  illustrates a process  700  of a new block being added to a distributed ledger  730 , according to example embodiments, and  FIG. 7B  illustrates contents of a block structure  750  for blockchain, according to example embodiments. Referring to  FIG. 7A , clients (not shown) may submit transactions to blockchain nodes  721 ,  722 , and/or  723 . Clients may be instructions received from any source to enact activity on the blockchain  730 . As an example, clients may be applications that act on behalf of a requester, such as a device, person or entity to propose transactions for the blockchain. The plurality of blockchain peers (e.g., blockchain nodes  721 ,  722 , and  723 ) may maintain a state of the blockchain network and a copy of the distributed ledger  730 . Different types of blockchain nodes/peers may be present in the blockchain network including endorsing peers which simulate and endorse transactions proposed by clients and committing peers which verify endorsements, validate transactions, and commit transactions to the distributed ledger  730 . In this example, the blockchain nodes  721 ,  722 , and  723  may perform the role of endorser node, committer node, or both. 
     The distributed ledger  730  includes a blockchain  732  which stores immutable, sequenced records in blocks, and a state database  734  (current world state) maintaining a current state of the blockchain  732 . One distributed ledger  730  may exist per channel and each peer maintains its own copy of the distributed ledger  730  for each channel of which they are a member. The blockchain  732  is a transaction log, structured as hash-linked blocks where each block contains a sequence of N transactions. Blocks may include various components such as shown in  FIG. 7B . The linking of the blocks (shown by arrows in  FIG. 7A ) may be generated by adding a hash of a prior block&#39;s header within a block header of a current block. In this way, all transactions on the blockchain  732  are sequenced and cryptographically linked together preventing tampering with blockchain data without breaking the hash links. Furthermore, because of the links, the latest block in the blockchain  732  represents every transaction that has come before it. The blockchain  732  may be stored on a peer file system (local or attached storage), which supports an append-only blockchain workload. 
     The current state of the blockchain  732  and the distributed ledger  732  may be stored in the state database  734 . Here, the current state data represents the latest values for all keys ever included in the chain transaction log of the blockchain  732 . Chaincode invocations execute transactions against the current state in the state database  734 . To make these chaincode interactions extremely efficient, the latest values of all keys are stored in the state database  734 . The state database  734  may include an indexed view into the transaction log of the blockchain  732 , it can therefore be regenerated from the chain at any time. The state database  734  may automatically get recovered (or generated if needed) upon peer startup, before transactions are accepted. 
     Endorsing nodes receive transactions from clients and endorse the transaction based on simulated results. Endorsing nodes hold smart contracts which simulate the transaction proposals. When an endorsing node endorses a transaction, the endorsing nodes creates a transaction endorsement which is a signed response from the endorsing node to the client application indicating the endorsement of the simulated transaction. The method of endorsing a transaction depends on an endorsement policy which may be specified within chaincode. An example of an endorsement policy is “the majority of endorsing peers must endorse the transaction”. Different channels may have different endorsement policies. Endorsed transactions are forward by the client application to ordering service  710 . 
     The ordering service  710  accepts endorsed transactions, orders them into a block, and delivers the blocks to the committing peers. For example, the ordering service  710  may initiate a new block when a threshold of transactions has been reached, a timer times out, or another condition. In the example of  FIG. 7A , blockchain node  722  is a committing peer that has received a new data block  750  for storage on blockchain  730 . 
     The ordering service  710  may be made up of a cluster of orderers. The ordering service  710  does not process transactions, smart contracts, or maintain the shared ledger. Rather, the ordering service  710  may accept the endorsed transactions and specifies the order in which those transactions are committed to the distributed ledger  730 . The architecture of the blockchain network may be designed such that the specific implementation of ‘ordering’ (e.g., Solo, Kafka, BFT, etc.) becomes a pluggable component. 
     Transactions are written to the distributed ledger  730  in a consistent order. The order of transactions is established to ensure that the updates to the state database  734  are valid when they are committed to the network. Unlike a cryptocurrency blockchain system (e.g., Bitcoin, etc.) where ordering occurs through the solving of a cryptographic puzzle, or mining, in this example the parties of the distributed ledger  730  may choose the ordering mechanism that best suits that network. 
     When the ordering service  710  initializes a new block  750 , the new block  750  may be broadcast to committing peers (e.g., blockchain nodes  721 ,  722 , and  723 ). In response, each committing peer validates the transaction within the new block  750  by checking to make sure that the read set and the write set still match the current world state in the state database  734 . Specifically, the committing peer can determine whether the read data that existed when the endorsers simulated the transaction is identical to the current world state in the state database  734 . When the committing peer validates the transaction, the transaction is written to the blockchain  732  on the distributed ledger  730 , and the state database  734  is updated with the write data from the read-write set. If a transaction fails, that is, if the committing peer finds that the read-write set does not match the current world state in the state database  734 , the transaction ordered into a block will still be included in that block, but it will be marked as invalid, and the state database  734  will not be updated. 
     Referring to  FIG. 7B , a block  750  (also referred to as a data block) that is stored on the blockchain  732  of the distributed ledger  730  may include multiple data segments such as a block header  760 , block data  770 , and block metadata  780 . It should be appreciated that the various depicted blocks and their contents, such as block  750  and its contents, shown in  FIG. 7B  are merely for purposes of example and are not meant to limit the scope of the example embodiments. In some cases, both the block header  760  and the block metadata  780  may be smaller than the block data  770  which stores transaction data, however this is not a requirement. The block  750  may store transactional information of N transactions (e.g.,  100 ,  500 ,  1000 ,  2000 ,  3000 , etc.) within the block data  770 . The block  750  may also include a link to a previous block (e.g., on the blockchain  732  in  FIG. 7A ) within the block header  760 . In particular, the block header  760  may include a hash of a previous block&#39;s header. The block header  760  may also include a unique block number, a hash of the block data  770  of the current block  750 , and the like. The block number of the block  750  may be unique and assigned in an incremental/sequential order starting from zero. The first block in the blockchain may be referred to as a genesis block which includes information about the blockchain, its members, the data stored therein, etc. 
     The block data  770  may store transactional information of each transaction that is recorded within the block  750 . For example, the transaction data may include one or more of a type of the transaction, a version, a timestamp, a channel ID of the distributed ledger  730 , a transaction ID, an epoch, a payload visibility, a chaincode path (deploy tx), a chaincode name, a chaincode version, input (chaincode and functions), a client (creator) identify such as a public key and certificate, a signature of the client, identities of endorsers, endorser signatures, a proposal hash, chaincode events, response status, namespace, a read set (list of key and version read by the transaction, etc.), a write set (list of key and value, etc.), a start key, an end key, a list of keys, a Merkel tree query summary, a user device biometric authentication, a file creator biometric authentication, a source file signature, an auxiliary data signature, a timestamp associated with a source file, and the like. The transaction data may be stored for each of the N transactions. 
     In some embodiments, the block data  770  may also store data  772  which adds additional information to the hash-linked chain of blocks in the blockchain  732 . Accordingly, the data  772  can be stored in an immutable log of blocks on the distributed ledger  730 . Some of the benefits of storing such data  772  are reflected in the various embodiments disclosed and depicted herein. 
     The block metadata  780  may store multiple fields of metadata (e.g., as a byte array, etc.). Metadata fields may include signature on block creation, a reference to a last configuration block, a transaction filter identifying valid and invalid transactions within the block, last offset persisted of an ordering service that ordered the block, and the like. The signature, the last configuration block, and the orderer metadata may be added by the ordering service  710 . Meanwhile, a committer of the block (such as blockchain node  722 ) may add validity/invalidity information based on an endorsement policy, verification of read/write sets, and the like. The transaction filter may include a byte array of a size equal to the number of transactions in the block data  770  and a validation code identifying whether a transaction was valid/invalid. 
       FIG. 8  is not intended to suggest any limitation as to the scope of use or functionality of embodiments of the application described herein. Regardless, the computing node  800  is capable of being implemented and/or performing any of the functionality set forth hereinabove. 
     In computing node  800  there is a computer system/server  802 , which is operational with numerous other general purpose or special purpose computing system environments or configurations. Examples of well-known computing systems, environments, and/or configurations that may be suitable for use with computer system/server  802  include, but are not limited to, personal computer systems, server computer systems, thin clients, thick clients, hand-held or laptop devices, multiprocessor systems, microprocessor-based systems, set top boxes, programmable consumer electronics, network PCs, minicomputer systems, mainframe computer systems, and distributed cloud computing environments that include any of the above systems or devices, and the like. 
     Computer system/server  802  may be described in the general context of computer system-executable instructions, such as program modules, being executed by a computer system. Generally, program modules may include routines, programs, objects, components, logic, data structures, and so on that perform particular tasks or implement particular abstract data types. Computer system/server  802  may be practiced in distributed cloud computing environments where tasks are performed by remote processing devices that are linked through a communications network. In a distributed cloud computing environment, program modules may be located in both local and remote computer system storage media including memory storage devices. 
     As shown in  FIG. 8 , computer system/server  802  in cloud computing node  800  is shown in the form of a general-purpose computing device. The components of computer system/server  802  may include, but are not limited to, one or more processors or processing units  804 , a system memory  806 , and a bus that couples various system components including system memory  806  to processor  804 . 
     The bus represents one or more of any of several types of bus structures, including a memory bus or memory controller, a peripheral bus, an accelerated graphics port, and a processor or local bus using any of a variety of bus architectures. By way of example, and not limitation, such architectures include Industry Standard Architecture (ISA) bus, Micro Channel Architecture (MCA) bus, Enhanced ISA (EISA) bus, Video Electronics Standards Association (VESA) local bus, and Peripheral Component Interconnects (PCI) bus. 
     Computer system/server  802  typically includes a variety of computer system readable media. Such media may be any available media that is accessible by computer system/server  802 , and it includes both volatile and non-volatile media, removable and non-removable media. System memory  806 , in one embodiment, implements the flow diagrams of the other figures. The system memory  806  can include computer system readable media in the form of volatile memory, such as random-access memory (RAM)  810  and/or cache memory  812 . Computer system/server  802  may further include other removable/non-removable, volatile/non-volatile computer system storage media. By way of example only, storage system  814  can be provided for reading from and writing to a non-removable, non-volatile magnetic media (not shown and typically called a “hard drive”). Although not shown, a magnetic disk drive for reading from and writing to a removable, non-volatile magnetic disk (e.g., a “floppy disk”), and an optical disk drive for reading from or writing to a removable, non-volatile optical disk such as a CD-ROM, DVD-ROM or other optical media can be provided. In such instances, each can be connected to the bus by one or more data media interfaces. As will be further depicted and described below, memory  806  may include at least one program product having a set (e.g., at least one) of program modules that are configured to carry out the functions of various embodiments of the application. 
     Program/utility  816 , having a set (at least one) of program modules  818 , may be stored in memory  806  by way of example, and not limitation, as well as an operating system, one or more application programs, other program modules, and program data. Each of the operating system, one or more application programs, other program modules, and program data or some combination thereof, may include an implementation of a networking environment. Program modules  818  generally carry out the functions and/or methodologies of various embodiments of the application as described herein. 
     As will be appreciated by one skilled in the art, aspects of the present application may be embodied as a system, method, or computer program product. Accordingly, aspects of the present application may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system.” Furthermore, aspects of the present application may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied thereon. 
     Computer system/server  802  may also communicate with one or more external devices  820  such as a keyboard, a pointing device, a display  822 , etc.; one or more devices that enable a user to interact with computer system/server  802 ; and/or any devices (e.g., network card, modem, etc.) that enable computer system/server  802  to communicate with one or more other computing devices. Such communication can occur via I/O interfaces  824 . Still yet, computer system/server  802  can communicate with one or more networks such as a local area network (LAN), a general wide area network (WAN), and/or a public network (e.g., the Internet) via network adapter  826 . As depicted, network adapter  826  communicates with the other components of computer system/server  802  via a bus. It should be understood that although not shown, other hardware and/or software components could be used in conjunction with computer system/server  802 . Examples, include, but are not limited to: microcode, device drivers, redundant processing units, external disk drive arrays, RAID systems, tape drives, and data archival storage systems, etc. 
     Although an exemplary embodiment of at least one of a system, method, and non-transitory computer readable medium has been illustrated in the accompanied drawings and described in the foregoing detailed description, it will be understood that the application is not limited to the embodiments disclosed, but is capable of numerous rearrangements, modifications, and substitutions as set forth and defined by the following claims. For example, the capabilities of the system of the various figures can be performed by one or more of the modules or components described herein or in a distributed architecture and may include a transmitter, receiver or pair of both. For example, all or part of the functionality performed by the individual modules, may be performed by one or more of these modules. Further, the functionality described herein may be performed at various times and in relation to various events, internal or external to the modules or components. Also, the information sent between various modules can be sent between the modules via at least one of: a data network, the Internet, a voice network, an Internet Protocol network, a wireless device, a wired device and/or via plurality of protocols. Also, the messages sent or received by any of the modules may be sent or received directly and/or via one or more of the other modules. 
     One skilled in the art will appreciate that a “system” could be embodied as a personal computer, a server, a console, a personal digital assistant (PDA), a cell phone, a tablet computing device, a smartphone or any other suitable computing device, or combination of devices. Presenting the above-described functions as being performed by a “system” is not intended to limit the scope of the present application in any way but is intended to provide one example of many embodiments. Indeed, methods, systems and apparatuses disclosed herein may be implemented in localized and distributed forms consistent with computing technology. 
     It should be noted that some of the system features described in this specification have been presented as modules, in order to more particularly emphasize their implementation independence. For example, a module may be implemented as a hardware circuit comprising custom very large-scale integration (VLSI) circuits or gate arrays, off-the-shelf semiconductors such as logic chips, transistors, or other discrete components. A module may also be implemented in programmable hardware devices such as field programmable gate arrays, programmable array logic, programmable logic devices, graphics processing units, or the like. 
     A module may also be at least partially implemented in software for execution by various types of processors. An identified unit of executable code may, for instance, comprise one or more physical or logical blocks of computer instructions that may, for instance, be organized as an object, procedure, or function. Nevertheless, the executables of an identified module need not be physically located together but may comprise disparate instructions stored in different locations which, when joined logically together, comprise the module and achieve the stated purpose for the module. Further, modules may be stored on a computer-readable medium, which may be, for instance, a hard disk drive, flash device, random access memory (RAM), tape, or any other such medium used to store data. 
     Indeed, a module of executable code could be a single instruction, or many instructions, and may even be distributed over several different code segments, among different programs, and across several memory devices. Similarly, operational data may be identified and illustrated herein within modules and may be embodied in any suitable form and organized within any suitable type of data structure. The operational data may be collected as a single data set or may be distributed over different locations including over different storage devices, and may exist, at least partially, merely as electronic signals on a system or network. 
     It will be readily understood that the components of the application, as generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations. Thus, the detailed description of the embodiments is not intended to limit the scope of the application as claimed but is merely representative of selected embodiments of the application. 
     One having ordinary skill in the art will readily understand that the above may be practiced with steps in a different order, and/or with hardware elements in configurations that are different than those which are disclosed. Therefore, although the application has been described based upon these preferred embodiments, it would be apparent to those of skill in the art that certain modifications, variations, and alternative constructions would be apparent. 
     While preferred embodiments of the present application have been described, it is to be understood that the embodiments described are illustrative only and the scope of the application is to be defined solely by the appended claims when considered with a full range of equivalents and modifications (e.g., protocols, hardware devices, software platforms etc.) thereto.