USP 8457545
`
`Description
`
`This application is a continuation of U.S. patent application Ser. No. 10/073,124, filed Feb. 9,
`2002 now U.S. Pat. No. 7,991,347; which is a continuation of application Ser. No. 09/812,003,
`filed Mar. 19, 2001 (now U.S. Pat. No. 6,349,409); which is a continuation of application Ser.
`No. 09/434,413, filed Nov. 4, 1999 (now U.S. Pat. No. 6,317,785); which is a continuation of
`application Ser. No. 08/939,368, filed Sep. 29, 1997 (now U.S. Pat. No. 6,021,307); which is a
`continuation in part of application Ser. No. 08/644,838, filed May 10, 1996 (now abandoned);
`which is a continuation in part of application Ser. No. 08/279,424, filed Jul. 25, 1994 (now
`abandoned); and application Ser. No. 08/255,649, filed Jun. 8, 1994 (now abandoned); which is a
`continuation in part of application Ser. No. 08/224,280, filed Apr. 74, 1994 (now abandoned); all
`of which are incorporated herein by reference.
`EFFICIENT CRYPTOGRAPHIC METHODS AND DEVICES
`
`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`
`The presentThis invention relates generally to information distribution and processing, and more
`specifically to an efficient cryptographic system that is designed to process a large amount of
`information by selectively encrypting a portion of the information.particularly to distributing
`information using a broadcast channel and a bi-directional communication channel.
`It has long been recognized that information needs to be encrypted under some
`circumstances. For example, military messages are typically encrypted in order to prevent
`enemies from obtaining information contained in the message. Recently, commercial
`applications of encryption have been proposed. For example, several commercial software
`products were developed to encrypt all or a portion of the data stored on a storage device (e.g.,
`hard disk and floppy diskette). Some of the communication software packages also allow users
`the option of encrypting their electronic mails. Recently, new methods for marketing information
`have been proposed. In one of the proposed methods, encrypted information is distributed (e.g.,
`using CD·ROMs or via digital highway, such as the Internet) by a vendor to potential customers
`either free or at nominal cost. However, the customers are not provided with the key to decrypt
`the information. When the customers wish to purchase the information, they need to contact the
`vendor to obtain the necessary decryption key, typically upon payment of fees. In another
`proposed method, a secure hardware is connected to the computer of a potential customer.
`Encrypted information (e.g., software) is distributed by a vendor to the customer either free or at
`nominal cost. The secure hardware contains the necessary key for decrypting the information.
`When the customer uses the information, the secure hardware decrypts the information and
`measures one or more parameters (e.g., time) relating to the usage of the information. The
`charges incurred by the customer is based on these parameters. Because the decryption key and
`the decrypted information is never exposed to the customer, the customer has to pay each time
`the information is used.
`
`One of the major differences between commercial applications of encryption and other
`applications (e.g., military applications) is the amount of information needs to be encrypted.
`Typically, commercial information, such as a database or a digitized movie, may contain more
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`Ex. 1026 - Page 1 of 15
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`Groupon, Inc.
`Exhibit 1026
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`than several hundred million bytes of information. On the other hand, military messages are
`relatively short. Another major difference is that commercial applications typically use low cost
`general purpose computers (such as microcomputers) to decrypt the encrypted data while
`military applications use high power computers specially designed for cryptographic
`applications. Even though the processing power of low cost computers is expected to increase at
`a fast pace, these computers take on more and more demanding tasks (e.g., video processing and
`high speed communication). As a result, the amount of processing power devoted to encryption
`in a commercial system may not increase with time, and in some situations, even decrease.
`
`Prior art cryptographic systems are mainly developed and designed for military applications, i.e.
`they are designed to use high power computers to handle a small amount of information. These
`systems may not be suitable for commercial applications. As a result, there is a need to develop
`an efficient method to handle commercial cryptographic needs.
`2. Description of the Prior Art
`
`Recent advances in modem and computer technology allow large amount of digital data to be
`transmitted electronically. A number of information providers (such as newspaper and magazine
`publishers) and on-line information distributors (such as America Online, Dialog and Nexis)
`have formed partnerships to deliver newspaper and other information on-line. In this system, a
`subscriber uses a computer and a modem to connect (e.g., through a regular phone line) to the
`computer of an on-line information distributor. The subscriber can retrieve information,
`including newspaper articles, stored in the computer of the information distributor.
`
`On-line delivery of newspaper has many advantages. For example, the information can be
`updated throughout the day while the printed version is printed only once or twice a day. Further,
`it is possible to do text-based searches on the information. However, it is found that on-line
`deliver of newspaper and other information is slow. For example, a subscriber has to wait many
`seconds for a newspaper article to be delivered. The quality of the electronic newspaper is low.
`For example, in order to reduce storage and communication requirements, graphic images
`appeared in the printed version are not universally supplied in the on-line version of newspaper.
`One of the reasons for such poor performance is the limited bandwidth of communication
`channels used by on-line information distributors. Another reason is that information is centrally
`processed by the computer at the site of the information distributor, with the result that each
`subscriber only gets a small slice of the time of the computer.
`
`Another way to communication information on-line is through the Internet, which is a worldwide
`interconnection of millions of computers, from low end personal computers to high-end
`mainframes. An important development in the Internet is the World Wide Web (the “Web”). The
`Web is a wide-area hypermedia information delivery and retrieval system aimed to give
`universal access to a large universe of documents. When the Web was first developed around
`1989, it was known to and used by the academic/research community only as a means for fast
`disseminating of information. There was no easily available tool which allows a technically
`untrained person to access the Web. An important development is the release of a Web
`“browser” around 1993. It has a simple but powerful graphic interface. The browser allows a
`user to retrieve web documents and navigate the Web using simple commands and popular tools
`such as point-and-click. Because the user does not have to be technically trained and the browser
`is easy to use, it has the potential of opening up the Internet to the masses.
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`A document designed to be accessed and read over the web is called a web page. Each web page
`must have an address in a recognized format—the URL, or Uniform Resource Locator—that
`enables computers all over the world to access it. Each web page has an unique URL. A web
`page typically contains both text and images. It is also possible to include audio and movie data.
`
`The Web faces the same problem as the regular on-line delivery of information. This is because
`most people use the above described modem to access the Internet. Thus, the data transfer rate of
`the Web is also limited. Because multimedia data (comprising a combination of text, graphic,
`video and/or audio) has a large data size, even when compressed, it could take a long time to
`retrieve a document from the Web. Further, it is difficult to prevent unauthorized persons from
`access a web page because more than 20 million people in the world has access to the Internet.
`
`Consequently, there is a need to have an improved system for distributing information
`electronically.
`SUMMARY OF THE INVENTION
`The present invention uses two channels to deliver digital information: a broadcast channel and a
`bi-directional channel. The broadcast channel is used to deliver the bulb of the digital
`information to subscribers. The amount of information delivered is preferably sufficient to
`satisfy the needs of a large number of subscribers so that they do not have to obtain additional
`information using the bi-directional channel. The broadcast information is stored on fast storage
`media located at subscriber sites. As a result, search and retrieval of the broadcast information is
`quick. Further, the broadcast information is processed locally using a dedicated on-site processor
`instead of relying on the computers of the information distributors. As a result, the load on the
`computers of the information distributors is reduced. If the subscribers desire to receive
`additional information relating to the broadcast information, the bi-directional communication
`channel is used to transmit the request and the requested information.
`Broadly stated. the present invention is a method and a signal processing device for encrypting
`information. Only a portion of the information needs to be encrypted because the information
`would not be useful if this portion is not decrypted. When the information has a low degree of
`correlation and error tolerance, even encrypting a small portion would be sufficient to render the
`information useless unless this small portion is decrypted. For information that is highly
`correlated, it would be difficult to take advantage of the correlation if substantially all the
`correlated portions are encrypted. As a result, the correlative nature of the information cannot
`be used to bypass decrypting the encrypted portion.
`The distribution costs of broadcast channels are typically much lower than that of a bi-directional
`communication channel. Consequently, the major portion of information is delivered using low
`cost distribution channels. For a large number of subscribers, the broadcast information will
`provide all the information they normally need. Thus, expensive bi-directional communication
`channels are used only occasionally.
`
`These and other features and advantages of the present invention will be fully understood by
`referring to the following detailed description in conjunction with the accompanying drawings.
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a schematic drawing showing onean embodiment of an information distribution system
`of the present invention.
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`FIG. 2A shows a newspaper article as displayed on a monitor of the information distribution
`system shown in FIG. 1.
`
`FIG. 2B shows the contents of the broadcast information which corresponds to the newspaper
`article of FIG. 2A.
`
`FIG. 2 is a drawing showing an3 shows another embodiment of the information distribution
`system of the present invention as applied to video information.
`
`FIG. 3 is a drawing showing4 shows an embodiment of the present invention where information
`is stored in a plurality of filesused in a data communication network.
`DETAILED DESCRIPTION OF THE InventionPREFERRED EMBODIMENT
`The present invention comprises a novel information distribution and processing system and
`related methods. The following description is presented to enable any person skilled in the art to
`make and use the invention. Descriptions of specific applications are provided only as examples.
`Various modifications to the preferred embodiments will be readily apparent to those skilled in
`the art, and the general principles defined herein may be applied to other embodiments and
`applications without departing from the spirit and scope of the invention. Thus, the present
`invention is not intended to be limited to the embodiments shown, but is to be accorded the
`widest scope consistent with the principles and features disclosed herein.
`It has been observed that information generally has a certain degree of redundancy. For
`example, the structure of many languages dictates that redundant words or letters be used at
`predetermined positions of a sentence. A reader can still understand the sentence if some of these
`words and letters are removed. For example, the grammar of the English language imposes a set
`of rules which includes putting the letter “s” at the end of a noun to designate plural quantity. In
`many sentences, the noun is not the only place where plural quantity is indicated. For example,
`the sentence “there are two birds” uses the word “two” to indicate the existence of more than
`one bird, in addition to the letter “s” attached to the word “bird.” Thus, the letter “s” at the end
`of the word “bird” can be omitted without affecting the meaning of the sentence. In fact, there
`are languages in this world in which noun does not have a plural form.
`
`The degree of redundancy in a certain piece of information depends on the nature of the
`information. At one extreme, information may contain many redundant parts. An example is
`video information which consists of a series of pictures depicting time progression of a scene.
`Each picture typically differs slightly from an adjacent picture in the series because the time
`difference in the scene depicted by adjacent pictures is typically less than 0.1 second. As a result,
`video information contains many pictures which are substantially the same. Consequently, it is
`easy to recreate a picture missing from the series by interpolating from the pictures prior and
`subsequent to the missing picture. This type of information is considered to have a high degree
`of temporal correlation. Video information also has another type of redundancy. The spatial
`variation of a picture is typically very gentle. For example, if the picture is a human swimming in
`water, there is little variation (in terms of color and intensity) in the portion of the picture relating
`to water. Consequently, it may be easy to recreate a missing portion of a picture by interpolating
`from portions of the picture surrounding the missing portion. This type of information is
`considered to have a high degree of spatial correlation.
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`At the other extreme is information in which it is difficult to create a missing portion
`from other portions. This type of information has a low degree of correlation. An example of this
`type of information is the binary code of a piece of software. Typically, it is difficult to recreate
`a missing byte (or a series of missing bytes) from other bytes in the binary code.
`
`Information can also be classified according to its effect on intended uses if a portion of
`the information is missing. At one extreme is information which would be useless if a small
`portion is missing. An example is the binary code of a piece of software. A computer is unlikely
`to successfully execute the software if the binary code has a few erroneous bytes. This type of
`information is considered to be error intolerant. At the other II extreme is information that
`degrades gracefully. For example, when noise of TV signal increases (i.e., portions of video
`information is missing or has erroneous values), color TV pictures often become monochrome.
`However, it is still possible to watch and comprehend the TV pictures, even though they are less
`pleasing to the eyes. This type of information is considered to be error tolerant. Error toleration
`can also be different depending on 1 spatial or temporal types of errors.
`
`It should be pointed out that even though the degree of error tolerance has some
`relationship to the degree of correlation of information, it does not depend solely on the degree
`of correlation. For example, a reader is likely to tolerate a large number of missing words in a
`newspaper article. On the other hand, the same reader probably would not tolerate the same
`percentage of missing words in a poem. Thus, even though the degree of correlation of the
`newspaper article and poem may be the same (because they follow essentially the same grammar
`rules), the degree of error tolerance is different. This is because error tolerance depends, to a
`certain extent, on subjective considerations. As another example, a person typically does not
`tolerate a small distortion in a familiar song while may tolerate a large distortion in a new song,
`even though the degree of correlation of these two songs are the same.
`
`In the prior art cryptographic systems, every bit of information is encrypted. One aspect
`of the present invention is the realization that it may not be necessary to completely encrypt the
`information, especially when it has a low degree of correlation. This is because it is often
`difficult to recreate the encrypted portion of information (if it cannot be decrypted) based on the
`clear portion of information. In addition, information that has a low degree of error tolerance
`may only need to be encrypted at a few critical places (e.g., the destination address of a jump op
`code, or the last name field of a customer database). This is because a user would not accept the
`information if a small portion is missing or erroneous. Thus, even though most of the
`information is in the clear, it is still not commercially useful if isolated portions are unavailable
`because they cannot be decrypted (i.e., people are still willing to pay a high price to obtain the
`full information, even though they already have percent of the information). Since only a small
`portion of information need to be decrypted, the amount of computation power required to
`decrypt the information is reduced.
`
`Encrypting a portion of information may also help to reduce the computation power
`required for other signal processing tasks. As an example, information which is massive and
`highly correlated (e.g., video information) is often compressed in order to reduce the amount of
`memory space used for storing and the bandwidth used for transmitting the information. Many
`compression methods make extensive use of the correlative nature of information. However,
`many encryption methods have a tendency to randomize information. For example, if the plain
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`text is a string of identical letters, the encrypted text using algorithms such as DES may be a
`string of letters in which every letter is different. Consequently, it may be more difficult to
`compress the encrypted text.
`
`The word “encryption” is used broadly in the present invention to include different ways
`of transforming information so that it is difficult for an 1 unauthorized person to correctly
`understand the information. It includes 1 transformation in which a key is required, such as
`public key and secret key encryption methods. It also includes scrambling information according
`to a secret algorithm without using a particular parameter which may be classified as a “key.”
`
`The word “information” is used broadly in the present invention to include data that is organized
`in some logical manner. Examples of information include video signal, audio signal, picture,
`computer software, text, database, and multimedia composition.
`The present invention can be used to solve the above described problem of digital information
`delivery. It uses two channels to deliver digital information: a broadcast channel and a bi-
`directional channel. The broadcast channel is used to deliver the bulb of the digital information
`from a source to subscribers. The time for broadcasting is preferably during a time of low
`communication load (e.g., off-peak hours). Upon receiving, the broadcast information is stored
`on storage media located at subscriber sites. If the subscribers desire to receive additional
`information relating to the broadcast information, the bi-directional communication channel is
`used to transmit the request and the requested information.
`
`The data transfer rate of the storage media (more than a million bytes per second) could be
`hundreds of times faster than that of a modem. As a result, search and retrieval of the broadcast
`information is quick. Further, the broadcast information is processed locally using a dedicated
`on-site processor instead of relying on the computers of the information distributors. As a result,
`the load on the computers of the information distributors is reduced. Even though the requested
`information is delivered using a regular low bandwidth communication channel, the performance
`of the system would not be severely affected because the requested information is only a small
`fraction of the broadcast information.
`
`In one embodiment of the present invention, the broadcast information can be sent in the clear
`while the requested information (which may contain commercially valuable information) is
`encrypted. Because the amount of requested information is a small fraction of the broadcast
`information, there is no need to use much computer resource to process the requested (and
`encrypted) information. In a different embodiment of the invention, the broadcast information is
`encrypted using a simple algorithm while the requested information is encrypted using a
`complex algorithm. Even though extra computer resource is used to decrypt the broadcast
`information, this embodiment may be useful for the case where it is not desirable for the public
`to view the broadcast information.
`
`It should be noted that the word “channel” is not limited to a specific kind of physical
`communication link. The word “channel” merely means a path for communicating information.
`The term “broadcast channel” means a path allowing an information source to deliver digital
`information to many recipients almost simultaneously. The term “bi-directional channel” means
`a path allowing one-to-one interactive communication between a source and a recipient. These
`two “channels” could use the same physical communication link (e.g., telephone lines, television
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`cable lines, wireless, optical links, etc.) to perform their respective functions. That is, the same
`physical communication link can support both broadcast and bi-directional channels.
`
`FIG. 1 is a block diagram showing one embodiment in whichof an information having a low
`degree of correlation is processed with a signal processor ofdistribution system 250 in
`accordance with the present invention. Fig. 1 shows the portion of information 1 containing
`sixteen pieces of plain text which are grouped into four blocks B1, B2, B3 and B4. Each block
`contains four pieces of plain text labeled as P1, P2, P3, and P4. Each of these sixteen pieces
`could contain a single bit or a plurality of bitsIn this embodiment, system 250 is designed to
`electronically distribute digital newspaper. It should be pointed out that the above grouping is
`exemplary, and any number of pieces could be grouped into any number of blocks. In addition, it
`is not necessary to require every block to have 1 the same number of pieces.system 250 can also
`be used advantageously to distribute other types of digital information. System 250 contains a
`plurality of subscriber units (such as units 252 and 254) each connected to a bi-directional
`communication channel (e.g., modems 256 and 258 coupled to units 252 and 254, respectively)
`and a satellite transponder 260 for broadcasting digital data to these subscriber units. Modems
`256 and 258 may be coupled to a database 259 via line-based or wireless telephone
`communications. In system 250, satellite transponder 260 is used to broadcast the content of a
`newspaper to the subscriber units while telephone modems 256 and 258 allow delivering
`additional information (stored in database 259) to subscriber units 252 and 254, respectively, on
`a demand basis.
`Processor 20 contains a program stored in memory, such as ROM 22. This 1 program is executed
`by a CPU 24. The program stored in ROM 22 could 1 be any program that can selectively
`encrypt some of the pieces of plain text in information 12. Preferably, an algorithm should be
`chosen such that it is difficult for an unauthorized person to determine which pieces are selected
`for encryption. Any encryption method can be used by processor 20.
`The structure of these subscriber units are substantially identical; consequently, only one of these
`units, such as unit 252, is described in detail. Unit 252 contains an antenna 266 for receiving
`broadcast signals from satellite transponder 260, a signal/data processor 268 for performing
`signal and data processing functions, a monitor 270 for displaying the digital newspaper, and an
`input device 272 (such as a keyboard and/or a mouse).
`An exemplary program in ROM 22 is described below. The pieces in the blocks having an odd
`numeral in their label, e.g., B1 and B3, are not encrypted. They provide the “base” for selecting
`one or more pieces in the subsequent blocks (i.e., blocks B2 and B4) for encryption. For
`example, the selected piece in block B2 can be calculated from the pieces in block B1 by adding
`the number of bits in all the pieces of block B1, and takes the remainder after dividing by four. It
`should be pointed out that the blocks used as base do not have to be adjacent to the blocks having
`pieces selected for encryption (e.g., the block B1 can be used to determine the selected piece in
`block B4). In addition, the pieces of more than one blocks can be used as base (e.g., blocks B1
`and B3 can be used to determine the selected piece in block B2).
`Signal/data processor 268 contains a transponder interface 282 for processing transponder signal
`received from antenna 266. Transponder interface 282 preferably contains a low noise receiver
`for receiving high frequency (e.g., C or Ku band) transponder signal and a universal data
`interface for converting the transponder signal to digital data. The retrieved data is stored in
`nonvolatile storage 284, such as a hard disk or solid state flash memory. Preferably, satellite
`transponder 260 broadcasts the newspaper data at predetermined times. Thus, a real-time clock
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`286 is preferably used to turn an interface 282 at the predetermined times. Processor 268
`contains a microcomputer 290 which coordinates the operation of clock 286, nonvolatile storage
`284, and interface 282. Microcomputer 290 preferably contains a central processing unit (CPU),
`random access memory (RAM) and peripheral interface devices. Processor 268 also contains a
`communication interface 292 for sending and receiving digital data from database 259 through
`modem 256.
`
`The time for broadcast is preferably chosen when communication load of transponder 260 is at a
`low level (e.g., around mid-night). As a result, the cost of information delivery is low.
`Alternatively, the time of broadcasting is chosen by transponder 260 because it knows when
`communication load is light. In this case, transponder 260 first sends a signal to signal/data
`processor 268 for alerting processor 268 to receive and process the newspaper information.
`
`A user can use the input device 272 and monitor 270 to read the content of the digital newspaper
`stored in nonvolatile storage 284. In one embodiment, the complete content of the newspaper is
`stored in nonvolatile storage 284. The term “complete content” means that the user is able to
`read the newspaper without relying on information stored in database 259 (although other
`embodiments may deliver less than the complete content). In this aspect, system 250 functions in
`a similar way as the distribution of a conventional printed newspaper. However, the digital data
`of the digital newspaper delivered by satellite transponder 260 preferably contains linkage
`references (such as pointers) which allow fast retrieval of additional information from database
`259.
`
`If the newspaper information received from satellite transponder 260 is sufficient to satisfy the
`needs of a user, signal/data processor 268 will not activate modem 256. However, if the user
`wishes to receive additional information relating to an item mentioned in the digital newspaper
`(e.g., by selecting the item using the input device), processor 268 will retrieve the information
`stored in database 259 using the embedded linkage reference.
`
`In system 250 of the present invention, the received digital newspaper (including graphics and
`other multimedia contents) is stored in nonvolatile storage 284, which has fast access time.
`Further, a dedicated processor (i.e., microcomputer 290) is used to process newspaper
`information. On the other hand, prior art on-line newspaper distribution systems rely on modem
`to deliver the content of the newspaper stored in a central site. Further, the processor in the
`central site has to serve many users in delivering the newspaper. As a result, system 250 has
`superior performance compared to prior art on-line newspaper delivery systems.
`
`In one embodiment of the present invention, commercially valuable information is encrypted and
`stored in database 259. The broadcast information does not contain this information. Thus, in this
`embodiment less than the complete content is delivered by the broadcast channel. In this case,
`the broadcast information would not be useful unless a decryption key is available to decrypt the
`information obtained from database 259. As a result, only subscribers who have a decryption key
`are able to obtain meaningful information from the newspaper. In the case, microcomputer 290
`also performs decryption functions. Alternatively, a separate decryptor 294 can be included in
`signal/data processor 268.
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`It should be appreciated that even though only one database is shown in FIG. 1, the valuable
`information could be distributed to several databases. Further, the digital newspaper and database
`259 could be physically located in the same site.
`
`If it is not desirable for the public to read the broadcast information, the data transmitted by
`transponder 260 could also be encrypted. In this case, simple encryption algorithm could be used
`to encrypt the broadcast information while complex encryption algorithm is used to encrypt the
`valuable information in database 259. A potential hacker would not be motivated to decrypt (and
`make public) the broadcast information unless he/she can also decrypt the valuable information.
`
`FIG. 2A shows an example of a portion of a newspaper article as seen on monitor 270. In FIG.
`2A, the terms which a user may obtain additional information are underlined (or highlighted in
`other ways, such as setting in different colors, depending on the choice of the publisher). If
`desired, the user may select these terms using an input device (e.g., a pointing device, such as a
`mouse), and signal/data processor 268 will obtain the additional information from database 259.
`
`FIG. 2B shows the same portion in FIG. 2A as transmitted by transponder 260 (for simplicity,
`other embedded formatting codes, such as center, bold, etc., are not shown). Each of the terms
`underlined in FIG. 2A are enclosed by a special symbol (e.g., the “γ” symbol) and followed by a
`linkage reference enclosed by another special symbol (e.g., the “
`
`” symbol). These symbols are invisible to the users and is recognizable only by microcomputer
`290. The linkage information could be as simple as a pointer.
`When an underlined term in FIG. 2A is selected by a user, microcomputer 290 extracts the
`linkage reference and transmits it to database 259. The linkage reference allows database 259 to
`retrieve the necessary information quickly without doing extensive searches. As a result, the
`response time of system 250 is fast. The retrieved information can itself contains linkage
`references and can be searched.
`
`If the speed of searching and retrieving data by database 259 is fast, it may not be necessary to
`include linkage reference in the broadcast information transmitted by transponder 260. In this
`case, the user selects (e.g., using an input device such as a mouse) words and terms he/she is
`interested in. Signal/data processor 268 transmits the selected items to database 259, which
`searches for matches in its database. Matched information is sent to subscriber unit 252 for
`processing.
`
`The bi-directional channel also allows updating of the broadcast information. There is typically a
`time difference between the broadcast and display of information. New information gathered
`during this time difference can be stored in database 259 and later tran