Abstract:
An independently verifiable system and method for the exchange of a sequence of tokens corresponding to units of currency. A credit or unit of currency is represented by a digital image referred to as a graphical token which may be displayed on an electronic viewing device or printed on paper. Each token contains a digital code that uniquely identifies the previous graphical token in a series of exchanges. After generating a token, a first user provides that token to a second user in order to initiate an exchange. The second user may choose to verify the validity and currency of the token before accepting the token. Either user may choose to register the token and any parameters associated with the exchange with a registry system. Once a user accepts a token, they may choose to issue a new token in the sequence. They may also choose to redeem the token for the credit associated with a sequence of tokens.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. §119(e) from U.S. Provisional Patent Application No. 60/975,357, titled “UnaBank—Better Service Futures,” filed Sep. 26, 2007, which is incorporated by reference herein in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to systems and methods for trading credit or the types of currency in exchange for goods or services. In particular, the present invention provides a means to robustly track the exchange of credit and support multiparty exchanges wherein participants in the exchange may collectively or individually redeem credits. 
     2. Description of the Related Art 
     Existing currency systems are not well-suited to multiparty transactions or transactions that extend across a range of time. Existing currencies presuppose individual ownership of the currency such that physical possession of a currency token is sufficient to trade, redeem and otherwise control that unit of currency. Furthermore, currency exchanges do not maintain a history. Given an individual unit of currency it is generally impossible to follow the trading history for that specific unit of currency. These properties imply that some of the individuals in multiparty transactions or transactions that extend over a range of time bear some risk that one of the other parties will abscond with the currency. 
     To overcome these limitations, people may employ cumbersome escrow institutions and contracts. Including these third-party institutions in a transaction is expensive, inefficient, and inappropriate for everyday use. 
     Therefore what is needed is a system and methods for exchanging, sharing, and redeeming credits that overcomes the limitations of existing systems and efficiently supports multiparty and extended transactions. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the deficiencies and limitations of the prior art by providing an independently verifiable system and method for the exchange of a sequence of tokens corresponding to units of currency. In one embodiment, a credit or unit of currency is represented by a digital image referred to as a graphical token which may be displayed on an electronic viewing device or printed on paper. Each token contains a digital code that uniquely identifies the previous graphical token in a series of exchanges. In one embodiment the exchange system of the present invention comprises: a token generation module, a registry system, a verification module, a hash module, and one or more user systems. These systems and modules may be connected to a network for communication with each other. The user systems preferably include a content module for storing the image data associated with graphical tokens and a token generation module to create new tokens to be used in exchanges. After generating a token, a first user provides that token to a second user in order to initiate an exchange. The second user may choose to use the verification module verify the validity and currency of the token before accepting the token. Either user may choose to register the token and any parameters associated with the exchange with a registry system. Once a user accepts a token, they may choose to issue a new token in the sequence using the token generation module. They may also choose to redeem the token for the credit associated with a sequence of tokens. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is illustrated by way of example, and not by way of limitation in the figures of the accompanying drawings in which like reference numerals are used to refer to similar elements. 
         FIG. 1A  is a flowchart of one embodiment of a method for generating a token according to the present invention. 
         FIG. 1B  is a flowchart of one embodiment of a method for generating a token containing transaction information according to the present invention. 
         FIG. 2  is a flow chart of one embodiment of a method for registering a token according to the present invention. 
         FIG. 3  is a flow chart of one embodiment of a method for verifying a token according to the present invention. 
         FIG. 4  is a block diagram of one embodiment of a system for exchanging, sharing and redeeming credits according to the present invention. 
         FIG. 5  is a graphical representation of example tokens according to the present invention. 
         FIG. 6  is a graphical representation of an example of another token according to the present invention. 
         FIG. 7  is a block diagram of another embodiment of a system for exchanging, sharing and redeeming credits according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An independently verifiable system and method for the exchange of a sequence of tokens are described. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the invention. It will be apparent, however, to one skilled in the art that the invention can be practiced without these specific details. In other instances, structures and devices are shown in block diagram form in order to avoid obscuring the invention. 
     Reference in the specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment. 
     As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having” or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such process, method, article or apparatus. Further, unless expressly stated to the contrary, “or” refers to an inclusive or and not to an exclusive or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present). 
     Some portions of the detailed descriptions that follow are presented in terms of algorithms and symbolic representations of operations on data bits within a computer memory. These algorithmic descriptions and representations are the means used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. An algorithm is here, and generally, conceived to be a self consistent sequence of steps leading to a desired result. The steps are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared and otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers or the like. 
     It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the following discussion, it is appreciated that throughout the description, discussions utilizing terms such as “processing” or “computing” or “calculating” or “determining” or “displaying” or the like, refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system&#39;s registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices. 
     Some embodiments may be described using the expression “coupled” and “connected” along with their derivatives. It should be understood that these terms are not intended as synonyms for each other. For example, some embodiments may be described using the term “connected” to indicate that two or more elements are in direct physical or electrical contact with each other. In another example, some embodiments may be described using the term “coupled” to indicate that two or more elements are in direct physical or electrical contact. The term “coupled,” however, may also mean that two or more elements are not in direct contact with each other, but yet still co-operate or interact with each other. The embodiments are not limited in this context. 
     The present invention also relates to an apparatus for performing the operations herein. This apparatus may be specially constructed for the required purposes, or it may comprise a general-purpose computer selectively activated or reconfigured by a computer program stored in the computer. Such a computer program may be stored in a computer readable storage medium, such as, but is not limited to, any type of disk including floppy disks, optical disks, CD-ROMs and magnetic optical disks, read-only memories (ROMs), random access memories (RAMs), EPROMs, EEPROMs, magnetic or optical cards, or any type of media suitable for storing electronic instructions, each coupled to a computer system bus. 
     Finally, the algorithms and displays presented herein are not inherently related to any particular computer or other apparatus. Various general-purpose systems may be used with programs in accordance with the teachings herein, or it may prove convenient to construct more specialized apparatus to perform the required method steps. The required structure for a variety of these systems will appear from the description below. In addition, the present invention is not described with reference to any particular programming language. It will be appreciated that a variety of programming languages may be used to implement the teachings of the invention as described herein. 
     System Overview 
     A system and method for the independently verifiable exchange of a sequence of tokens is described. More specifically, the present invention is a process implemented as a software solution that can operate on a wide variety of computing platforms. In the present invention a sequence of tokens is used by participants in one or more exchanges. The sequence itself represents a store of value which may be denominated in a currency. Alternatively the value of a sequence may correspond to reputation, promises of hours of labor, or some other measure of worth. The first token in a series comprises a unique digital image generated by an agent recognized within the community of exchange to have the authority to issue original tokens. This agent provides an initial value or backing for the sequence of tokens. In one embodiment, the token issued by the agent has a face value that corresponds to the amount of a national currency, such as the US dollar, which the agent has deposited into an escrow account to serve as the backing for the sequence of tokens. Each subsequent token is another digital image which contains a machine readable identifier, e.g. a barcode such as a QR Code, containing a unique identifier calculated as a function of the digital image of the previous token. In one embodiment, this function is a secure hash function, such as the SHA1 algorithm. Applying this function to the image data of the previous token creates a digital fingerprint unique to that image data. Embedding that fingerprint within a barcode included in the image of a token creates an immutable link from a token to the previous token in the sequence. This sequence can be independently verified by any party that has access to all of the images in this sequence simply by calculating the identifier, e.g. the hash, for each token, decoding the barcodes in each token to recover the embedded identifiers and then confirming for all tokens that the embedded identifiers for a token correspond to the calculated identifier for the previous token. To facilitate the exchange and verification of tokens, token holders may register tokens with a registry system which stores the image data associated with each token and allows that data to be retrieved by using the identifier for that token, e.g. the hash of the image data. 
     Generating a Token 
     Referring now to  FIG. 1A , the operation of a token generation module is described. In one embodiment, this module operates locally on a user&#39;s computing device retrieving and storing token images to a local data store. In an alternate embodiment, this module operates on a Web server allowing users to upload and download token images using their web browser. To generate a new token, the token generation module receives in step  110  the token image data associated with the current token. In step  112 , the token generation module calculates the unique identifier for the current token by computing the results of a function known as a secure hash algorithm applied to the image data. In one embodiment, this function is the SHA1 algorithm which is well known in the art. 
     In step  114 , the token generation module then generates a digital image containing a barcode with the unique identifier for the current token. In one embodiment, this barcode is a QR Code™ from Denso Wave Incorporated. 
     The token generation module then creates a template image data stream that is a copy of the current token image data. In an alternate embodiment, this new image data stream can be a copy of a canonical template image for the sequence of currency associated containing the current token. In step  116  of  FIG. 1A , the token generation module composites the digital image containing the barcode with the unique identifier for the current token onto the template image data stream to generate the image data for the new token. The new token image data is then sent back to the requestor. In one embodiment the token image data is also sent to the registry system using the HTTPS protocol. 
       FIG. 1B  shows an alternate embodiment in which the token generation module generates tokens that reference the specific transaction grammars in addition to the previous token. In this embodiment, the token generation module receives a set of transaction parameters to be referenced by the new token as shown in step  121 . These transaction parameters include a reference to the current token image data, such as a URL. In step  122  the token generation module uses the image data reference to retrieve the current token image data. In an alternate embodiment, this image data is supplied along with the transaction parameters. 
     As before, the unique identifier for the current token image is calculated using the secure hash function in step  112 . In step  123 , a transaction identifier is calculated. In one embodiment, this transaction identifier is decorated by applying a secure hash function, such as the SHA1 algorithm, to the transaction parameters. 
     In step  124 , the unique identifier for the current token image and the transaction identifier are concatenated. In one embodiment, a new exchange identifier is generated by applying a secure hash function to these concatenated identifiers. This new exchange identifier is then encoded in a newly generated barcode image. In an alternate embodiment, the newly generated barcode image directly encodes the concatenated token image identifier and transaction identifier. 
     The token generation module may also create tokens that include information specific to an exchange and make it easier for humans to visually distinguish and verify the token images. In one embodiment, the transaction parameters include a reference to a thumbnail image to be included on the new token. This image might be, for example, a small picture of the older of the current token. In step  125 , this thumbnail image data is retrieved and made available for compositing onto the new image data stream in addition to the archive image data in order to generate the new token image data. 
     Registering a Token 
     Once the image data for a token has been generated, the holder of a token may wish to register that token with a registry system in order to allow the token and any subsequent tokens to be easily validated by other parties. In one embodiment, the registry system allows individual token identifiers to be registered along with any transaction parameters associated with the exchange of that token. 
     Registration begins when the registry system receives the token image data and any associated transaction parameters. As before, the registry system computes the unique identifier for the token image data in step  212 . The registry system then stores  230  that token image data and any associated transaction parameters in a storage module such as a local file system or database. The unique identifier for the token is used as a key for later retrieval of the image data and transaction grammars. For example on a computer running a version of the LINUX operating system, the image data might be stored in a file with a filename or path “/IMAGES/TOKENID” and the transaction data might be stored in a file with the filename “/TRANSACTIONS/TOKENID” where TOKENID represents the unique identifier associated with the token. 
     In order to facilitate rapid verification and redemption of token images, the registry maintains some additional information about registered tokens. In one embodiment, this additional information includes CURRENT, OLD, and PENDING markers which are stored in locations associated with the token identifiers. To determine the marker for the token being register, the registry system processes the token image data to extract the previous token identifier contained within the machine-readable identifier, e.g. a barcode, embedded within the token image data as shown in step  240 . This previous token identifier should correspond to the unique identifier of the previous token in the sequence that was used to generated the token being registered. 
     If the previous token was registered with the registry, then the storage module should contain an entry for the previous token identifier. Using the example pathnames above, “/IMAGES/PREVTOKENID”, where PREVTOKENID is the unique identifier of the previous token, should exist and contain the image data associated with the previous token. Step  250  checks the existences of this entry to see if the previous token has been registered. 
     If the previous token has been registered, the registry system retrieves the marker associated with the previous token in step  252 . If that previous token is marked CURRENT, then the marker for the previous token is changed to OLD in step  254  and the marker for the token being register is set to CURRENT in step  270 . Otherwise if the previous token has been registered but is not marked CURRENT, then the marker for the current token is set to PENDING. In one embodiment if the marker for the previous token is set to REDEEMED, then registration of the current token is not allowed and an error message is sent back in response to the request for registration. 
     If the previous token is not registered in step  250  or in the case where the token being registered does not contain any machine-readable identifier, then the registry system checks to see if the token is an authorized “original issue” token, in other words it checks to see if this token is an authorized start of a new token sequence. In step  260 , the registry system examines the transaction parameters to see if they contain authorization for originating a new token. In one embodiment, this authorization consists of a digital signature using a private encryption key issued to a party trusted by the registry system. 
     If the token is an authorized a original issue, then the token is marked CURRENT in step  270 , otherwise the token is marked as PENDING in step  280 . 
     In one embodiment, the registry system maintains a list of all the tokens which are marked PENDING, for example by storing the token id of each such token in a file with pathname “/PENDING/PREVTOKENID” where PREVTOKENID is the identifier invented in the machine-readable data of the token image of the PENDING token. Whenever a token T is marked as CURRENT, the registry to see if there are any PENDING tokens with references to token T. If so, the registry marks T as OLD and marks each PENDING token as CURRENT. In one embodiment, the registry does not allow the registration of multiple children for any token, so an attempt to register a token will fail if the machine-readable code contained in the token image data of the token is PREVTOKENID and PREVTOKENID is encoded in the image data of an already registered token. 
     Since tokens may be used for many different types of exchanges, the registry system may accept and store many different types of transaction parameters. In one embodiment, the transaction parameters include an account ID for the current holder of the token, an account ID for the new holder of a token, and an authorization code to allow the registration. In one embodiment, the transaction parameters also include a representation of the additional currency that has been placed in escrow as part of the transaction associated with this token. 
     Verifying a Token 
     One key advantage of the present invention is the ability to independently verify a sequence of tokens.  FIG. 3 . is a flow chart of one embodiment for verifying a sequence of tokens given the image data corresponding to the tokens. The method shown in  FIG. 3  assumes that the verification module has access to the markers associated with each token as stored in a registry system. The verification process might obtain this information by requesting them from the registry system using HTTP requests or other communication methods. In an alternate embodiment, the verification process first involves the creation of a registry of all of the token images provided for verification and then that registry system is used in the verification process. 
     To begin the verification process step  335 , the verification module receives or retrieves image data associated with the token to be verified. The image data is then processed, step  240 , to extract the machine-readable identifier encoded within the image data, the machine-readable identifier corresponding to the previous token identifier. For example a QR Code™ decoding algorithm is applied to the token image data. 
     The previous token identifier is used to retrieve  345  the previous token image data associated with that previous token identifier. If that previous token image data is not available, then the verification process fails. Assuming the previous token image data is available then the verification module confirms the integrity of the previous token image data, the unique identifier for that image data is calculated by applying the secure hash function in step  312 . The output of that calculation is compared with the previous token identifier decoded from the image data of the token being verified in step  350 . If those identifiers do not match the verification fails in step  390 . 
     If the identifiers do match, then the marker associated with previous token identifier is retrieved in step  352 . If that identifier is marked CURRENT, then the verification of the token succeeds in step  370 . This means that the token image data being verified was generated based on a token that the registry considers valid and that the token image data may be registered as the next token in the sequence. 
     If the previous token identifier is not marked CURRENT, then the token being verified may not be accepted by the registry for registration and therefore the verification process reports  380  NOT CURRENT. This indicates that the token being verified is part of a sequence of tokens but may not be able to be registered either because the token has already been registered or another token has been registered which has the same previous token identifier encoded in the image data for that other token. 
     In another embodiment, the verification process begins with a set of token images, and one or more of which are designated as “original” token images. For each token image to be verified, the verification module extracts the previous token identifier as in step  240 , retrieves the previous token image. If no previous token identifier can be extracted or there is no image in the set of token images having that identifier, then the verification process reports a failure for the token being verified. If the previous token image is found within the set and is labeled as original, the verification process reports success for the token being verified, otherwise if the previous token image is found within the set then these steps are repeated for that previous token image. 
     Another advantage of the present invention is the ability to print the token graphics on paper or display them on a viewing screen and readily verify the tokens using an independent imaging system. In one embodiment, an imaging system such as a digital camera is used to create an image data stream which is processed as in step  240  to extract the machine-readable ID, e.g. using a QR Code decoder that corresponds to the previous token in the sequence. Note that if the printed token has already been registered, then the previous token referenced by the printed token will be marked as OLD allowing the verifier to confirm that the printed token is part of a sequence originating with a verified token. This may be useful as part of an audit of a series of transactions. 
     If the previous token referenced by the printed token is marked as CURRENT, then the holder of the token knows that they can use the printed token to generate a new token image and register that new token image. This provides a mechanism for exchanging tokens via paper. Note that in systems which only allow any registered token to have only one child token, e.g. systems which enforce a single sequence with no branching, the potential exists for a race condition to occur. In that race condition, a token image which was previously verified as referencing a CURRENT token, Q, may be prevented from being registered because another token image referencing Q may have been registered causing the marker for Q to change to OLD. To avoid such race conditions, authentication mechanisms such as passwords may be used in conjunction with the token registration. In one embodiment, the transaction parameters for a previous token image contain the hash of a password to be provided upon registration of the subsequent token image. Before registering the subsequent token image, the registry system checks the transaction details supplied with the subsequent token image for a password, calculates the hash of that password and registers the subsequent token image if and only if the password is included in the transaction details of the subsequent token and the hash of the password matches the hash provided in the transaction details of the previous token. 
     In another embodiment, the transaction parameters associated with a token X include contact information for the token holder. This contact information might include e-mail address or mobile phone number. When the registry receives a request to register a token subsequent to token X, the registry sends a unique, secret code in a request to the contact information included in the transaction parameters for token X. The registration for the subsequent token is marked PENDING until the code is received. In an alternate embodiment, the PENDING registration is automatically accepted unless a code sent to the contact information for X is received within a specified deadline. These approaches allow great decrease of flexibility in the exchange of tokens while maintaining the integrity and independent verifiability of the sequence of exchanges. 
     The foregoing description of the embodiments of the present invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the present invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the present invention be limited not by this detailed description, but rather by the claims of this application. As will be understood by those familiar with the art, the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Likewise, the particular naming and division of the modules, routines, features, attributes, methodologies and other aspects are not mandatory or significant, and the mechanisms that implement the present invention or its features may have different names, divisions and/or formats. Furthermore, as will be apparent to one of ordinary skill in the relevant art, the modules, routines, features, attributes, methodologies and other aspects of the present invention can be implemented as software, hardware, firmware or any combination of the three. Also, wherever a component, an example of which is a module, of the present invention is implemented as software, the component can be implemented as a standalone program, as part of a larger program, as a plurality of separate programs, as a statically or dynamically linked library, as a kernel loadable module, as a device driver, and/or in every and any other way known now or in the future to those of ordinary skill in the art of computer programming. Additionally, the present invention is in no way limited to implementation in any specific programming language, or for any specific operating system or environment. Accordingly, the disclosure of the present invention is intended to be illustrative, but not limiting, of the scope of the present invention, which is set forth in the following claims.