Abstract:
A system and method for determining whether wager data for players&#39; wagers placed on a drawing game have been altered after winning game elements are drawn includes a host computer and a verification device. The host computer stores the wager data and generates a first hash value for the wager data at a time prior to drawing the winning game elements. The host computer is capable of generating a second hash value for the wager data at a time subsequent to drawing the winning game elements for comparison to the first hash value. The verification device receives the first hash value for the wager data prior to drawing the winning game elements and receives the winning game elements.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a system for playing a wagering game based on a drawing, and in particular, a system for determining whether wagers have been altered after winning game numbers are drawn. 
     Lottery and keno games are typical wagering games in which a gaming authority conducts periodic drawings of winning elements such as winning game numbers. In such games, each player selects a series of game elements, e.g., game numbers chosen from a set of numbers, which the player believes will be drawn during a subsequent drawing of winning game numbers from the set of numbers. For example, in a lottery game, a player may select six game numbers from the set of integers 1 through 40 which the player believes will match six winning game numbers drawn by the gaming authority. Similarly, in a keno game, a player may select 10 game numbers from the set of integers from 1 through 80 which the players believes will match 10 out of 20 numbers drawn by the gaming authority. Drawings for lottery games typically occur once or twice a week, while drawings for keno games can occur at intervals as short as several minutes. 
     Drawing games such as lottery and keno games are typically played using electronic gaming systems. Such electronic gaming systems include geographically dispersed gaming terminals for placing players&#39; wagers. The terminals are connected to a host computer that usually records wagering information relating to the players&#39; wagers in an electronic storage device such as a magnetic medium. 
     For security purposes, an electronic gaming system requires a mechanism for ensuring that existing wagering information is not altered after the drawing of winning game numbers to create a fraudulent wager containing game numbers that match the winning game numbers. The alteration may be any modification, deletion, addition or corruption of the wagering information. Several methods have been used to determine whether wagering information has been altered after a drawing of winning game numbers. 
     For games in which drawings occur once a day or less often, an electronic or printed copy of the wagering information for all wagers placed on the game can be made and secured at a remote location before the winning game numbers are drawn. At any time after the drawing, the secure copy of the wagering information can be compared to the wagering information stored in the host computer on a record-by-record basis to determine whether any alterations were made to the wagering information. This technique is time consuming, and is difficult to use with games in which drawings occur every few minutes. 
     A second technique involves use of an internal control system (ICS) connected to the host computer to perform auditing functions. In addition to recording the wagering information for every wager in the host computer, a copy of the wagering information for each wager is sent to the ICS. Before the winning game numbers are drawn, the ICS must assure that it has received a copy of all wagering information for the game. Thus, there must be no technical failures of the system or loss of communication between the gaming terminals and the host computer prior to the drawing. To perform the auditing function properly, the ICS must also be able to determine independently that the winning game numbers have not been drawn when the last wager is placed. 
     A third technique involves writing all wagering information to a fixed medium such as a write once removable media (WORM) drive. Once wagering information has been written to the WORM drive, it cannot be altered. This technique helps to prevent alteration of wagering information, but does not determine whether any alterations have been made prior to writing the wagering information to the WORM drive. A limitation of a WORM drive is that its use requires ensuring that all wagering information has actually been written to the WORM drive prior to drawing the winning game numbers. 
     SUMMARY OF THE INVENTION 
     In general, in one aspect, the invention features a system for determining whether wager data for players&#39; wagers placed on a drawing game have been altered after winning game numbers are drawn. A host computer stores the wager data and generates a first hash value for the wager data at a time prior to drawing the winning game elements, the host computer being capable of generating a second hash value for the wager data at a time subsequent to drawing the winning game elements for comparison to the first hash value. A verification device receives the first hash value for the wager data prior to drawing the winning game elements and receives the winning game elements. 
     Implementations of the invention may also include one or more of the following features. The wager data may include players&#39; game numbers and wager amounts. 
     The host computer may generate an intermediate hash value prior to generating the first hash value. The host computer may generate a transaction hash value for each of the players&#39; wagers. The host computer may generate a first digital signature to uniquely identify the host computer, and append the first digital signature to the first hash value. 
     The verification device may generate a combination hash value for the winning game elements and the first hash value, and transmit the combination hash value and the winning game elements to the host computer. The host computer may generate a check hash value for the winning game numbers and the first hash value, and compare the check hash value to the combination hash value. The verification device may generate a second digital signature to uniquely identify the drawing device, and append the second digital signature to the combination hash value. 
     The host computer may include a memory for storing the wager data and the first hash value. The system may further include a gaming terminal for generating the wager data. The system may further include a drawing device for drawing the winning game elements. The system may also include an auditing device in communication with the host computer for generating a third hash value for the wager data and comparing the first hash value to the third hash value. 
     In general, in another aspect, the invention features a method of detecting whether any of a plurality of stored wager data for players&#39; wagers placed on a drawing game has been altered after winning game elements are drawn. A first hash value for the plurality of stored wager data is generated before the winning game elements are drawn. A second hash value for the plurality of stored wager data is generated after the winning game elements are drawn. The first hash value is compared to the second hash value. 
     Implementations of the invention may also include one or more of the following features. The method may further include determining that at least a portion of the plurality of stored wager data has been altered based on a comparison of the first hash value and the second hash value. The method may also include transmitting the first hash value to an independent location before the winning game elements are drawn. 
     The first hash value and the second hash value may be generated using a one-way hashing function. The method may include generating an intermediate hash value based on a portion of the plurality of stored wager data prior to generating the first hash value. The method may also include generating a transaction hash value based on the stored wager data for each of the players&#39; wagers. 
     In general, in another aspect, the invention features a method of securing a plurality of wager data for players&#39; wagers placed on a drawing game. A wager data hash value for the plurality of wager data is generated at a first location. The wager data hash value is sent to a second location. The winning game elements are drawn. A combination hash value for the wager data hash value and the winning game elements is generated at the second location. The winning game elements and the combination hash value are transmitted to the first location. 
     Implementations of the invention may also include one or more of the following features. The method may include generating a check hash value for the wager data hash value and the winning game elements at the first location, and comparing the combination hash value to the check hash value. The method may also include appending a digital signature to the combination hash value at the second location. 
     An advantage of the present invention is that alterations of wager data after drawing the winning game numbers can be detected without having to make a copy of all of the wager data before the winning game numbers are drawn and without having to make a record-by-record comparison of the wager data before and after the drawing. 
     An additional advantage of the present invention is that alteration of wager data may be easily detected by a computer with limited processing and storage capacities. 
     A further advantage of the present invention is that wager data may be secured prior to drawing the winning game numbers for a game having any drawing frequency and using any drawing method, e.g., manual or electronic. 
     Other features and advantages of the invention will become apparent from the following detailed description, and from the claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagrammatic sketch of a gaming system according to the present invention. 
     FIGS. 2A and 2B are a flow chart showing the operation of the gaming system of FIG.  1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention relates to the use of hash values and digital signatures to enhance the security of wager data for a drawing game. A unique hash value for the wager data is generated before the winning game numbers are selected. If the wager data is altered after the winning game numbers have been selected, a hash value subsequently generated for the altered wager data will not match the original hash value for the wager data. 
     A hash value is a fixed numerical value or string of digits generated from text, i.e., a string of text characters. The hash value is a numerical representation of the contents of the text, and is smaller than the text in that it may be stored in less memory space than the text itself. The hash value is preferably generated by a one-way hashing function, which is a formula or algorithm applied to the text for which it is extremely unlikely that the same hash value will result from applying the hashing function to a different text. 
     A digital signature is a digital code attached to an electronically transmitted message that uniquely identifies the sender of the message. A one-way hashing function may be used to create the digital signature. 
     FIG. 1 shows a gaming system  10  for determining whether wagers have been altered after winning game numbers have been drawn. FIGS. 2A and 2B are a flow chart showing a method  100  of operating gaming system  10  to determine whether wagers have been altered after winning game numbers have been drawn. 
     Gaming system  10  includes a gaming terminal  20 , a host computer  30 , and a verification device  40 . These components of gaming system  10  may communicate with each other over a network  35 . Network  35  is preferably a secure, private network. Network  35  may also be the Internet or any communications network such as a dial-up, hard-wired or wireless digital network. Any data, messages or files transmitted over network  35  may be encrypted for security. 
     A player places a wager for a drawing game at gaming terminal  20  (step  110 ). For example, the player may tender a wager amount in the form of cash money to an operator of the gaming terminal in exchange for a gaming ticket printed by the gaming terminal including the player&#39;s game numbers and the wager amount. System  10  may also include a plurality of similar gaming terminals  22  . . .  24  connected over network  35 . 
     Gaming terminal  20  generates wager data including the player&#39;s game numbers and wager amount (step  120 ). The player&#39;s game numbers may be selected by the player or chosen randomly, e.g., using a random number generator  26  to perform a “quick-pick” function. The wager data may also include other data pertaining to the player&#39;s wager, such as the amount wagered, the date of the wager, the game for which the wager was made, the location of gaming terminal  20 , the name of the player, non-wager transactions and wager pool totals. 
     Wager data generated by gaming terminal  20  is transmitted to host computer  30  over network  35  (step  130 ). Host computer  30  includes a processor  32  and a memory  34  for processing and storing data transmitted to the host computer from gaming terminal  20 . Memory  34  further includes a journal file  36  for storing data pertaining to gaming transactions processed by the host computer. 
     At some point before winning game numbers are drawn for a drawing game, all wagering for the game is stopped (step  140 ). In the meantime, host computer  30  accumulates all of the wager data for a particular game in journal file  36  (step  150 ). Processor  32  applies a hashing function to generate a wager data hash value H 1  for at least the game numbers and wager amounts of all of the players&#39; wagers for the game (step  160 ). The hashing function is preferably a one-way hashing algorithm and can be, e.g., MD5, SHA, or any other strong cryptographic method. The wager data hash value H 1  is stored in memory  34  (step  170 ). 
     If there is too much wager data to handle quickly or efficiently, or if too much time is required to generate the wager data hash value H 1 , then intermediate hash values h 1  . . . h 3  may be generated at predetermined intervals for portions of the wager data being accumulated for the game (step  152 ). Each intermediate hash value h 1  . . . h 3  may be generated based on all of the new wager data pertaining to wagers made during a time interval as well as the intermediate hash values generated during previous intervals. 
     If sufficient calculating time is available, it may also be possible to generate a transaction hash value T 1  . . . T 2  for each individual wager (step  154 ). Thus, the transaction hash value is calculated from a subset of all of the wager data generated for the drawing game. The transaction hash values T 1  . . . T 2  may then be stored in journal file  36  along with the wager data, with intermediate hash values h 1  . . . h 2 , or with wager data hash value H 1 . Storing transaction hash values T 1  . . . T 2  provides a simple way of determining which transactions may have been altered. 
     Host computer  30  may also create a digital signature S 1  based on wager data hash value H 1  to uniquely identify the host computer. The digital signature may be created using a cryptographic signature algorithm, e.g., DSS. Digital signature S 1  is stored in memory  34  and appended to wager data hash value H 1  (step  180 ). 
     Verification device  40  is an independent location which receives the wager data hash value. Verification device is associated with one or more drawing devices  46 ,  48 , which draw the winning game numbers. Verification device  40  may also include a processor  41  and a memory  42 . 
     Host computer  30  transmits wager data hash value H 1  with appended digital signature S 1  to verification device  40  prior to the drawing of the winning game numbers (step  190 ). By checking digital signature S 1 , e.g., using public key cryptography, verification device  40  can verify that the wager data hash value was sent by the correct host computer. 
     After the wager data hash value has been received and digital signature S 1  has been verified, winning game numbers N 1  . . . N 6  for the drawing game are selected by drawing device  46  and transmitted to the verification device (step  210 ). Verification device  40  may store the winning game numbers in memory  42  and transmit the winning game numbers to host computer  30 , which stores the winning game numbers in the memory  34  (step  220 ), and to a distribution medium  50  for transmitting the winning game numbers to the players of the game by, e.g., closed-circuit television, publicly-accessible television or printed publication (step  230 ). 
     Verification device  40  also uses a hashing function to generate a combination hash value H 2  based on both the wager data hash value H 1  and the winning game numbers N 1  . . . N 6  (step  240 ). Verification device  40  transmits combination hash value H 2  to host computer  30  (step  260 ). The verification device may also create a digital signature S 2  based on combination hash value H 2  and append digital signature S 2  to the combination hash value so that host computer  30  can verify the authenticity of the verification device that transmitted the winning game numbers (step  250 ). 
     After receiving the winning game numbers from verification device  40 , host computer  30  verifies that the winning game numbers were transmitted by the correct verification device. Host computer  30  then applies a hashing function to both wager data hash value H 1  and winning game numbers N 1  . . . N 6  to generate a check hash value H 3  (step  280 ). The host computer authenticates the winning numbers N 1  . . . N 6  received from the verification device by comparing combination hash value H 2  to check hash value H 3  (step  290 ). If these hash values are the same, then the winning game numbers N 1  . . . N 6  received by host computer  30  are deemed to be authentic. 
     To determine whether any wager data for the drawing game has been altered, the hash value for the wager data may be recalculated at any time for the wager data stored in journal file  36  (step  300 ), and compared to the original wager data hash value H 1  (step  310 ). It would be nearly impossible to alter any of the wager data without affecting the recalculated hash value for the wager data. If the recalculated hash value for the wager data differs from the original wager data hash value H 1 , then the gaming authority may conclude that some of the wager data has been altered. The gaming authority may then search through the stored wager data to determine which portion of wager data was altered. 
     The data stored in memory  34  and the contents of journal file  36  may also be copied and transmitted to an independent auditing device  60 , e.g., by digital electronic transmission or by physical delivery of the data. Auditing device  60  uses wager data hash value H 1 , combination hash value H 2 , winning game numbers N 1  . . . N 6 , the original wager data or transaction hashes T 1  . . . T 2 , and digital signature S 2  of verification device  40  to verify the following: 
     1. Only correct wagers were included in the drawing game, and none of the wager data was altered; 
     2. The verification device that transmitted the winning game numbers was the correct verification device; and 
     3. The winning game numbers transmitted by the verification device were the same as those recorded in the journal file. 
     Either host computer  30  or auditing device  60  may recalculate the hash value for the wager data at any time to ensure that none of the wager data was altered and that no wagers were made after the original wager data hash value H 1  was sent to verification device  40 . 
     Other embodiments are within the scope of the following claims.