Interactive television security through transaction time stamping

A system for providing security on an interactive television system. Two sets of interactive data, with time stamps, are separately sent to a remote location. At the remote location, the time stamps are checked against a remote clock, a time difference being noted for both sets of data. The two time differences are compared to determine if one set of data has been delayed as compared to the other. Non-delayed data can be used to update a game score for an interactive game. After the game is completed, the remote clock is compared to a central clock. The difference between the two clocks are compared to the time difference for non-delayed data to determine whether the entire aggregate of interactive data was delayed.

CROSS-REFERENCE TO RELATED APPLICATIONS 
This application is related to the following application, which is assigned 
to the assignee of the subject application: 
"TRANSACTION BASED INTERACTIVE TELEVISION SYSTEM", inventors John P. 
Lappington Susan K. Marshall, Wayne Y. Yamamoto, and Cameron A. Wilson, 
Application SC/No. 08/159,930, filed Nov. 30, 1993. 
Both of the above related applications are incorporated herein by 
reference. 
BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention is directed to maintaining security in an interactive 
television system. Particularly, the interactive television system is 
adapted for use with existing broadcast, cable, and satellite television 
or radio or other communication systems for allowing participants and 
viewers to interact with the system in order, by way of example only, to 
shop, enter into games of skill, and engage in educational presentations 
and other events where information is provided and the participant or 
viewer can make an appropriate response thereto. 
2. Description of the Related Art 
Many interactive television products have been introduced that provide the 
capability for the viewer to participate in television programs. These 
products accept cue signals transmitted to handheld devices that measure 
and control the response of the viewers as the viewers participate in the 
program. Some of these devices implement hardware that monitors the 
response or the results of responses accumulated over time and reports the 
results to a central site. One of the early embodiments of this technology 
was the QUBE interactive two-way television system introduced by Warner 
Communications at least as early as 1982. Other systems include the INDAX 
system field tested at least as early as 1984 by Cox Communications. 
The interactive television products currently known fall generally within 
one of two categories. The first category includes systems having firmware 
in a remote participant's handheld device such that the participant can 
start playing along with the interactive program as soon as the programs 
begins. Such a system has limited capabilities in regard to supporting 
multiple varieties of interactive programs due to the size limitation and 
permanence of the firmware. The second category maintains the software in 
random access memory in the viewer's handheld device such that the program 
must be downloaded into the device prior to the event starting. This 
process may take up to five minutes, requiring the participant to wait 
prior to participating in the interactive program. Both categories of 
devices are designed to work with one interactive program at a time, where 
the participant must complete that program before being able to 
participate in a new program. 
When the above described products are compared to the television viewing 
habits of most viewers, significant deficiencies are apparent. Most 
viewers do not continuously watch one program. Viewers generally switch 
between several channels. This is so pervasive in the industry that the 
terms "grazing" and "surfing" have been given to the habit of switching 
between channels during the programs. 
None of the prior art interactive systems allow for interactive programs to 
be presented concurrently on different television channels so that a 
viewer may change channels ("graze" or "surf") during the middle of a 
first interactive program and join a second interactive program already in 
progress. This would also be a useful feature for a viewer who turns on 
the television late or who wants to take part in more than one program 
that overlaps. For example, a viewer may want to play along with a 
football game but interact with an educational program during halftime. 
Or, if the viewer starts playing one game and realizes that he or she does 
not like the program, then the viewer can change channels and join a 
second program that is already in progress. 
Furthermore, the prior art system requires a viewer to schedule an 
interactive program in order for the system to download the program and 
tune to the correct television signal, or the viewer must tune the 
interactive system to the correct channel. Thus, if a viewer wishes to 
change programs (or surf) the viewer must change the television tuner and 
the interactive television system tuner. 
Accordingly, an interactive system concept that is compatible with the 
participants viewing habits is required for interactive television to be 
successful. This system must include the ability to interleave (or surf 
between) several interactive programs at the same time and not require a 
significant amount of advance downloading of programs or initialization 
information. When the viewer tunes the channel, the viewer should almost 
immediately be able to participate in the interactive program either if 
the viewer is for the first time watching that program or the viewer is 
returning after watching some other program for a brief or extended 
period. 
In the situation where a viewer returns to a program that was previously 
watched, the interactive game should continue, leaving out only the part 
that was missed. Any cumulative score for the part of the event actually 
participated in should be maintained. The result should be the same as if 
the missed questions were not answered. 
The interactive systems described above and others being introduced into 
the marketplace contemplate allowing the viewers to play, for example, a 
game of chance or other game where the viewer's response is scored. The 
scoring is eventually used to determine whether the viewer has achieved a 
certain success level and is deserving of a prize. Alternatively, an 
interactive system may contemplate having a viewer enter survey responses 
where certain responses or methods of responding will make the viewer 
eligible for a prize. Prizes could be awarded to attract more viewers to 
play interactive games or as a promotion for a consumer product or 
service. However, if valuable prizes are awarded, for example, airline 
tickets, automobiles and electronic appliances; viewers will have an 
incentive to falsify and inflate their score. 
The general problem arises when the transmitted signal is delayed by taping 
with a VCR or other technique. A typical interactive program could include 
displaying a message, asking a question, answering the question, revealing 
the correct answer and rewarding the viewer with points based on the 
viewer's answer. If a viewer had access to a live feed and was able to 
receive the transmitted questions and answers at the handheld from a 
delayed source, the viewer could know the answers to the questions before 
they were asked by the handheld. The handheld would not know that the 
interactive program was delayed and would treat it as any other game. This 
would enable the viewer to fool the handheld and receive a score higher 
than the viewer deserved. 
SUMMARY OF THE INVENTION 
The present invention is directed to overcome the disadvantages of the 
prior art. 
It is, therefore, an object of the present invention to provide for an 
interactive television system that guards against cheating. It is also the 
intent not to unduly restrict the use of the system in order to achieve 
this result. 
As described above, delaying transmitted signals can potentially compromise 
an interactive system. The only difference between the actual and the 
delayed interactive data signal is the absolute transmission time. A 
defense against such an attack would involve knowledge of the absolute 
time by the handheld. If the handheld knew the absolute time, it could 
check an embedded time stamp in the received interactive data against the 
absolute time to see if it were valid. If data was received that did not 
match the current absolute time, the handheld would know that it was 
delayed and treat the data accordingly. 
The security system of the present invention includes a time stamping 
technique that uses, preferably, an internal handheld clock and an 
imbedded time stamp within the interactive data. The time stamp would be 
generated by a data insertion system based on a real time clock. If the 
handheld clock were required to always be synchronized to the actual time, 
the handheld could determine if the received interactive program was live 
or taped. However, to require that the handheld clock be synchronized to 
the actual time is difficult for several reasons. First, crystals precise 
enough to keep the actual time over an extended time period would be 
expensive. Second, the handheld clock would have to be factory set and 
periodically reset through some sort of registration procedure. And third, 
the tolerance of the handheld clock would place restrictions on the type 
of question that could be asked. For example, if the interactive program 
required the viewer to guess whether a strike or a ball will be pitched 
during a baseball game, and the tolerance of the handheld clock was plus 
or minus 15 seconds, a viewer could still cheat using a transmitted signal 
delayed by five or ten seconds. Typical crystals can drift by as much as 
two to three minutes over a single year which would further restrict the 
type of questions that could be asked in an interactive game. 
The suggested solution to this problem is not to rely on absolute time but 
to rely on relative times. The handheld would keep track of the difference 
between the handheld clock and a reference clock. The reference clock 
would be monitored by reading a time stamp embedded in the interactive 
data. The difference between the embedded time stamp and the handheld 
clock would be compared for successive sets of interactive data, to 
determine whether one of the sets is delayed as compared to the other. 
This comparison enables the handheld terminal to determine which scores to 
eliminate and which scores to add to the cumulative score. Eventually, the 
difference between the handheld clock and the time stamp must be compared 
to the difference between the handheld clock and the actual reference 
clock used to generate the time stamp. This is done when the handheld 
score is registered. For example, through coded numbers, a viewer can 
telephone a central operator and report the current value of the handheld 
clock and the score to determine whether the score was generated by live 
interactive data, and thus valid. This process could, of course, be 
automated through appropriate software. 
In one embodiment of the present invention, the method for providing 
security for interactive television comprises the steps of receiving 
interactive data for a first transaction (or unit of interactive data), 
the interactive data including a first time stamp based on a central 
clock. A remote clock is then read and a first delta is calculated. The 
first delta represents the first time stamp subtracted from the remote 
clock. The process is then repeated for a second transaction; therefore, 
obtaining a second delta. A discrepancy is then calculated equal to the 
first delta subtracted from the second delta. If the discrepancy is 
greater than a first time drift constant, then the second transaction was 
delayed as compared to the first transaction. If the discrepancy is less 
than the negative of the first time drift constant, then the first 
transaction was delayed as compared to the second transaction. If the 
absolute value of the discrepancy is less than the first time drift 
constant, than neither transaction is delayed in relation to the other. 
Furthermore, if the discrepancy is greater than the first time drift 
constant, the delta from the first transaction is stored as a stored 
delta. If the discrepancy is not greater than the first time drift 
constant, the stored delta is equal to delta from the second transaction. 
The remote clock is read for a third time and the time difference is 
calculated between the central clock and the third remote clock value. A 
time offset is calculated equal to the stored delta subtracted from the 
time difference so that the cumulative score is determined to be valid if 
the absolute value of the time offset is less than or equal to a second 
time drift constant. 
Another embodiment of the present invention comprises means for receiving 
interactive data having a time stamp based on a central clock. The system 
also includes a remote clock and timing means for comparing the time stamp 
to the remote clock. Comparison means, based on the timing means, 
determines whether a first subset of the interactive data is delayed as 
compared to the second subset of the interactive data. Presentation means, 
based on the first subset of data, presents the transaction to the viewer 
and scores the viewer's response. The system may include a means for 
sending the cumulative score of an interactive program to a central 
location to verify whether the interactive data was received in a delayed 
manner based on a comparison of the central clock with the remote clock. 
Verification means, based on the comparison means, the central clock and 
the remote clock, determines if the interactive data was delayed. If the 
interactive data was determined not to be delayed, then the cumulative 
score is valid. 
In yet another embodiment of the present invention, the method for 
providing security includes inserting a time stamp, based on a central 
clock, into a first set of interactive data. The first set of interactive 
data is then sent to a remote location. The remote location has a remote 
clock so that a first delta can be determined for the first set of 
interactive data. The first delta being equal to the difference between 
the time stamp and the remote clock. The first delta is compared to a 
delta of a second set of interactive data to determine if the first set of 
interactive data is delayed as compared to the second set of interactive 
data. A remote delta and remote clock value are then received. The remote 
delta is the same value as the first delta if the first set of interactive 
data is not delayed as compared to the second set of interactive data. A 
time difference is determined between the central clock and the remote 
clock value. The time difference is compared to the received delta in 
order to determine whether the interactive data was delayed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
I. System Overview 
FIG. 1 shows interactive system 10. An authoring system 12 is used to 
create/program interactive data. That is, a programmer (also called a 
script writer) develops a set of questions or informational statements to 
be sent to a viewer during a television broadcast. Questions could also be 
accompanied by responses, response criteria and/or scoring criteria. The 
script writer could also determine when during the broadcast the questions 
should be transmitted and presented, and how a question will fit into an 
overall game or series. A script writer using authoring system 12 creates 
commands and event specific data, which are used to present the 
interactive program to a viewer. 
After a script writer creates the interactive program, the interactive data 
is first sent to data insertion control 14, which controls the insertion 
of interactive data preferably into the vertical blanking interval ("VBI") 
of incoming television signal 16. Television signal 16 can be, for 
example, a show to be aired on a network such as a sitcom or baseball 
game. Insertion control 14 utilizes Insertion Card 20 to insert the 
interactive data onto television signal 16. 
There are four different modes for inserting data onto the VBI. The first 
mode is a straight insertion. Interactive data is designed using authoring 
system 12 and is sent to data insertion control 14, which places it 
immediately into the VBI of television signal 16 to create encoded signal 
22. Encoded signal 22 can be immediately transmitted to home viewers or 
video taped. A second mode is to pre-produce the interactive data with 
time data. Data insertion control 14 would insert the interactive data 
onto the VBI at the appropriate time. Third, the information could be 
pre-produced for real time insertion into a live event. In this situation 
the data would be stored in a memory device and an operator would, via a 
control panel, signal when a given transaction should be encoded on to the 
VBI. Finally, it is contemplated that interactive data could be designed 
and synchronized to a specific video frame. 
Insertion Card 20 adds (or encodes) the interactive data to the VBI lines 
of television signal 16, and sends the encoded television signal 22 to a 
transmitter, all at the direction of data insertion control 14. Data 
insertion control 14 is responsible for processing, scheduling, time 
stamping and validation, as well as administrative functions associated 
with data insertion. Device driver 18 serves as an interface between 
Insertion Card 20 and data insertion control 14. In an alternative 
embodiment, rather than using the VBI lines, interactive data could be 
transmitted using the audio portion of a television signal, luminance, 
digital packets or radio communication. 
Encoded television signal 22 can be sent from satellite transmitter 24 and 
received by a satellite receiver 26. It is contemplated that satellite 
receiver 26 could be part of a cable system where the signal received by 
satellite receiver 26 is then sent via cable TV to home viewers. Instead 
of using a satellite and a cable system, the television signal could be 
broadcast using a standard television transmitter, transmitted using 
straight cable without satellites or transmitted with any other means for 
transmitting a television signal. 
The signal received by satellite receiver 26 is sent to the home viewer 
where it is received by television set 30 and settop device/converter 28. 
Television 30 plays the original television program. Settop device 28 
receives the encoded television signal and strips out the interactive 
data. Settop device 28 sends the interactive data by infrared transmission 
to handheld 32, which presents the interactive program to the home viewer. 
Thus, while the home viewer watches TV 30, the viewer can participate in 
the interactive program presented on handheld 32. Although infrared 
transmission is preferred, any other means for transmission will suffice; 
for example, radio communication or a wire. Transmission via infrared or 
radio is preferred so many viewers, each with their own handheld, can 
participate simultaneously. 
Upon completion of an interactive program the viewer could register his/her 
score with operations 34, which would be a central or regional office for 
collecting scores, survey information, etc. Registering can be 
accomplished utilizing many alternatives. The preferred method for 
registering scores includes handheld 32 transmitting, via infrared 
communication, the registration information to dialer 33. After receiving 
the registration information, dialer 33, which includes a modem, sends the 
information to operations 34. 
Alternative methods for registering scores include a home viewer reading a 
code from handheld 32 to an operator over conventional telephone lines, 
the viewer inputting a code into a central computer using the touch tone 
keys on the telephone, or including a modem inside handheld 32 so that 
handheld 32 can communicate over the telephone lines with a computer at 
operations 34. It is also contemplated that a viewer could contact 
operations 34 via a radio signal, cable or another communication medium. 
FIG. 2 shows the interactive system configured to add an interactive 
program to a pre-existing television signal that is on a video tape or 
equivalent. Play tape deck 40 is used to play source tape 42, which 
contains the pre-recorded television program. Play tape deck 40 can be 
used to read time codes from source tape 42 or there can be a time code 
generator inserted between the play tape deck 40 and the time code reader 
44. Time code reader 44 reads the timing information in order to determine 
when data may be inserted, and transmits this information to data 
insertion control 14. As described with respect to FIG. 1, data insertion 
control 14, in conjunction with device driver 18 and Insertion Card 20, 
inserts interactive data into the signal emanating from source tape 42. 
The encoded signal is sent to record tape deck 46 and recorded on encoded 
tape 48, which will contain the pre-recorded television program plus the 
interactive data. Encoded tape 48 can then be stored for later broadcast. 
When a television program (live or pre-programmed) with interactive data is 
broadcast, the interactive data will be transparent to viewers that do not 
have the interactive system. That is, someone without handheld 32 will not 
know that an interactive data is being presented. 
Each of the components described above in regard to FIG. 1 will be 
discussed in more detail below. 
II. Authoring System 
As described above, the authoring system is the software application used 
to create interactive programs. The preferred embodiment authoring system 
12 is a computer (IBM PC 386 or 486, or any other programmable computer) 
using authoring system software (a windows application) that generates 
interactive data including commands and event specific data. While the 
script writer is designing an interactive program, a script file is 
created that includes an English-like description of the various questions 
and answers etc., for an interactive program. Authoring system 12 includes 
a two part compiler. During the first phase of the compilation, a symbolic 
file is created from the script file. The symbolic file is analogous to 
source code associated with a typical computer program. During the second 
phase of the compilation, an object file is created from the symbolic 
file. The object file contains commands and event specific data that is 
read by the data insertion system. The commands could be part of a 
proprietary high level command language or any other assembly-like 
commands. 
When the interactive program is at the creation stage, on authoring system 
12, it is called a script. The fundamental building block of a script is 
called a scripit. A scripit is a stand alone element that does not require 
another scripit to function. Examples of scripits include messages, 
questions, responses, criteria, and tables (to be explained below). An 
aggregate of scripits make up a script. 
A transaction is the compiled version of a scripit or group of scripts 
which is time oriented. That is, all the data for a transaction is sent to 
handheld 32 at one time. Examples of transactions include messages, 
questions, responses, scoring criteria, branching conditions or a 
combination thereof. A group of one or more transactions make up a 
segment. A segment is a group of transactions that must be played 
sequentially. For example, a segment may include a transaction asking a 
question, a transaction disclosing the correct answer, a transaction 
scoring the viewer's response, a transaction providing the viewer with 
feedback or a combination thereof. Each transaction is numbered so that 
the first transaction in a segment is assigned a transaction number of 
one. 
Thus, a script writer designs a script, and the script is compiled and 
broken down into a series of transactions which are sent to handheld 37. 
There are several types of scripts which can be designed separately or in 
combination, for example: standard mode, live events, polling, program or 
series, mini-games, or pay-per-play. A standard mode script can be either 
encoded onto a video tape or sent to data insertion 14 to be inserted in 
the VBI of a television signal in accord with the timing information 
programmed by the script writer. Live event scripts are to be used with 
live events, for example, sports, news and talk shows. With a live mode 
script, the script writer has selected text but does not insert timing 
information into the script. Rather, the script writer just sends a 
transaction at the appropriate time. 
A polling script allows an opportunity for viewers to talk back to their 
television. Polling scripts gather information from the audience, 
including who they are, where they are and what they like. A polling 
script is used in conjunction with viewers calling in their scores. 
Applications include a teaser for news and talk shows. For example, a 
script could ask questions related to the next episode and then provide 
the poll results at the beginning of the next show. Or, the polls can be 
used as a comparison device, asking viewers questions, then later 
revealing where their opinions rank in relation to other viewers. It can 
also be used to rate the programs on a particular network and voice their 
opinions on what types of programming they would prefer. Finally, it can 
be used as a source for market research, verifying viewership and audience 
demographics. 
Series scripts allows a number of individual games to be grouped into a 
series. This allows a programmer to devise on-going games in which 
player's scores can accumulate from game to game with a running tally 
(cumulative score) stored in handheld 32. An example of a series script is 
a interactive program designed to be played along with all seven games of 
the world series. 
Mini-games are complete games (groups of one or more segments) within a 
script. Mini-games allows the viewer to play self-contained games within 
games. For example, a game show may have 3 contests during the program. 
Each contest could be a mini-game. Mini-games have unique properties and 
conditions that make them integral and useful parts of scripts, such as 
not automatically updating the cumulative score after each transaction or 
segment. The script writer can choose to update the cumulative score with 
the mini-game score at the completion of the mini-game, or save the 
mini-game score to be used for another mini-game. For example, if a script 
is being developed for a football game, the script writer can choose to 
report the viewer's scores by quarters. At the end of each quarter, the 
accumulated points for the quarter will be posted to the total. 
Special programs or series can be designated as pay-per-play events. 
Interactive programs created for pay-per-play programming are only 
available to viewers who pay pre-registration fees. A special access code 
given to viewers who pay the fee allows handheld 32 to receive the 
transactions that are a part of the pay-per-play event. The pay-per-play 
feature can be used to create high stakes competitions as well as for 
premier and special events. Such programs utilize the event specific 
programmer tables, discussed below. 
Scripts can be written with different levels of play which can be sent 
simultaneously to all handhelds 32. This feature allows a programmer to 
tailor scripts to different skills, ages and interests. Viewers chose 
their game level and then receive questions only for that level of play. 
A script has three main components: messages, questions, and responses. 
Messages are text displayed on handheld 32 that do not require input from 
the viewer. Messages can introduce a show or provide information about the 
program. For example, a message may state, "Hello, welcome to the Super 
Bowl." Questions are text that request input from the viewer. There are 
preferably six types of questions: Yes/No, True/False, Multiple Choice, 
Integer, Decimal, and Fill In The Blank. 
Responses are scoring methods and messages, based on an answers entered by 
a viewer. For example, if the viewer correctly answers a multiple choice 
question, the viewer could be awarded 25 points and a message would be 
displayed stating, "Great, you earned 25 points." In the preferred 
embodiment, there are preferably seven response options from which to 
choose: Quick and Easy, Multiple Replies, Closest, Count Down, Save Into, 
Threshold, and In-Range. 
Quick and Easy displays one message for a right answer and one message for 
a wrong answer. Multiple Replies can display a unique message for each 
answer, with up to seven possibilities. For example, a question may have 
three acceptable answers, with one of the answers worth more points. The 
script writer can design a scripit such that a different reply message and 
point value will be given for each of the three answers. Closest includes 
one response for answers in a predetermined range and one response for 
answers out of the range. When scoring an answer for a question using the 
Closest option, variable points are awarded based on distance from the 
right answer. The closer a viewer's answer is to the correct answer, the 
more points the viewer receives. For Count Down, there is one message for 
the right answer and one answer for all others. Variable points are 
awarded based on the amount of time a viewer takes to input the correct 
answer. The faster a viewer answers a question, the more points are 
received. 
With the Save Into option, no message is displayed for an answer. Rather, 
the answer is stored in a register for future use. The threshold option 
awards points and displays a message when the viewer correctly answers a 
predetermined number of questions. For example, if the viewer is playing 
along with Jeopardy and guesses 8 out of 10 questions correctly, the 
viewer will be awarded points. For In Range responses, there is one 
message for answers within a predetermined range and another message for 
answers outside the range. The predetermined range is programmed by the 
script writer. 
Every script is uniquely identified by a combination of three numbers: 
mailbox number, group number and unit number. This identification 
structure is one of the features which allows viewers to switch or surf 
between programs while ensuring that the handheld 32 maintains the 
information associated with each interactive program. 
An affiliate is the owner and/or producer of a script, who may hire a 
script writer (or be the script writer) to create a script and who would 
pay for the air time to broadcast a script. Examples of affiliates include 
but are not limited to, networks, advertisers, production companies or 
sporting event organizers. 
Handheld 32 stores scores, opinions and other data in memory units called 
programmer tables. Each affiliate is assigned a number of programmer 
tables according to the particular affiliate's needs so that no two 
affiliates can use the same programmer table. The mailbox number is a 
unique number assigned to each of the affiliate's programmer tables. The 
authoring system 12 only allows an affiliate to create interactive 
programs which utilize programmer tables assigned to that affiliate. 
The group number assigned to a script identifies the group (or series) of 
scripts to which the script belongs. This number is stored in the 
programmer table. For many scripts, one episode is its own group; 
therefore, the group number assigned to it is unique. However, the 
interactive system has the capability to combine the scores of a series of 
scripts. The group number must be the same for each script in the series 
so that handheld 32 knows which series the script belongs to. 
The unit number assigned to a script is important when the script is a part 
of a series. The unit number must uniquely identify each episode of a 
series, and is stored within the assigned programmer table. When the 
script is a stand-alone script (e.g. not part of a series) the unit number 
is usually set to one. Scripts that are a part of a series have the same 
group number and preferably mailbox number so that scores from the various 
games in a series can be accumulated in a single register. Alternatively, 
multiple programmer tables, each with it's individual mailbox number, can 
be used with the individual scripts or programs of a series such that the 
score registers (discussed below) of each programmer table is added 
together. Each script is differentiated from the others in a series by its 
unique unit number. When a new script is sent on the VBI, handheld 32 
checks the assigned programmer table to determine whether the group number 
from the previous script is the same or different from the current script. 
If the group number is the same, the handheld 32 will assume that the 
current script is a part of a series. 
FIGS. 3A-3E are flow charts depicting how the authoring system is used to 
create a script. Authoring system 12 has a main menu 60 which offers six 
sub-menus: file menu 62, edit menu 64, scripit menu 66, system menu 68, 
window menu 70, and help menu 72. 
If a script writer selects the file menu 62, the script writer is given 
eight options. The script writer can choose to create a "new" file 74, 
which enables a script writer to create a new script. The script writer 
can also choose to open an existing script 76. The script writer can save 
a script 78 if that script has already been saved before. If this is the 
first time the script writer is saving the script, the script writer would 
select "save as" 80. Print 82 allows the script writer to print the script 
file, and print format 84 allows the script writer to print the script 
file setting the format. Printer setup 86 allows the script writer to 
select the printer set-up parameters, and exit 88 allows the script writer 
to exit the authoring system software. 
The edit menu 64 allows the script writer to cut 90, copy 92 or paste 94 
text. The system menu 68 allows the script writer to enter script 
information, for example, the name of a script and author. The script 
writer can also define pre-stored messages or pre-stored questions, define 
defaults and name or re-name any variables or registers. Window menu 70 
allows the script writer to view quick buttons 96, which are icons that, 
when selected, perform functions that normally would take more than one 
action. Help menu 72 includes information about the authoring system 80 
and an index 100 to that information. 
Script menu 66, described in more detail in FIG. 3B, is chosen when a 
script writer is creating scripits. The script writer can create a message 
102, a question 104, a table 106, a score registration 108, a mini-game 
110 or a branching instruction 116. If the script writer chooses to create 
a message 102, then the script writer is presented with the message window 
102 (FIG. 3C) which gives the option of creating/modifying a message 118 
or leaving the message window 132. If the script writer chooses to 
create/modify a message 118, the script writer can enter the frame number 
120 for the scripit, the name of the message 122, and a description of the 
message 124. The script writer would then enter a message into text box 
126, which would be a window having a blank line. The script writer has 
the "Send To" option 128 with condition 130 to restrict which viewers will 
receive the message. For example, the script writer can choose to send the 
scripit to all viewers who have scored above 700 points or all viewers 
based on demographic data. If the script writer does not choose any 
restrictions then every viewer playing along with the script would receive 
the message. 
The script writer has four options when leaving the message window 132. The 
OK icon 134 saves all of the information that has been entered by the 
script writer. Alternatively, the script writer can use the cancel icon 
136 which returns to the main menu without saving any of the information 
input by the script writer, or the script writer can delete 138 all 
information in the message window and return to the main menu 60. The 
script writer can also choose to select system menu close icon 140, which 
causes the script writer to exit the authoring system software. 
Question window 104 is used when a script writer in the script menu 66 
chooses to create a question (FIG. 3D). The script writer has an option to 
create or modify a question 142 or leave the question window 152. If the 
script writer chooses to create or modify a question 142, the script 
writer enters the frame (or time code) information 144, the name of the 
question 146 and a description of the question 148. The script writer then 
enters a question into the text box 150. The script writer can choose to 
restrict the viewers who receive the information 162 and 164 (see 
discussion with regard to icons 128 and 130 in FIG. 3C). The script writer 
can leave the question window 152 by selecting the OK icon 154, cancel 
icon 156, delete icon 158 or system menu close icon 160 (as described with 
respect to FIG. 3C). 
Before leaving the question window, the script writer has the option to set 
a question characteristic 166 and/or open question response 168. 
Setting the question characteristics 166 includes setting the defaults; for 
example, whether the response typed in by the viewer on handheld 32 should 
be echoed back, whether any tone should accompany prompts and restricting 
the amount of time a viewer has to enter a response. 
When the script writer chooses the Open Question Response window 168, the 
script writer is given several alternatives for the response type (FIG. 
3E). If the script writer chooses Quick and Easy 170, the script writer 
must enter the correct answer, the points awarded for the correct answer, 
the reply displayed on handheld 32 if the viewer selects the correct 
answer and the reply displayed if the viewer selects the wrong answer. 
If the script writer chooses Multiple Replies 172, the script writer enters 
a set of correct answers, the number of points awarded for each correct 
answer and messages for each of the correct answers. 
If the script writer chooses Closest 174, the script writer enters the 
correct answer, defines the range of answers in which viewers will score 
points and determines the maximum amount of points to be awarded. The 
script writer must also input the text to be displayed by handheld 32 when 
the viewer inputs an answer in the defined range. Handheld 32 uses a 
predetermined formula for allocating points for answers inside the defined 
range. For example, if the correct answer is 50, the acceptable range of 
answers is 30 to 70, and a viewer guesses 40, then the viewer would be off 
by 50% and would only receive 50% of the maximum allowed points. 
Alternatively, scoring could be allocated using a bell curve. 
##EQU1## 
If the script writer selects Count Down 176, the script writer enters the 
correct answer, the maximum number of points possible, the answer time 
interval and the number of points to decrement per time interval. After 
the viewer is presented with a question, the clock in handheld 32 begins 
to run. At every time interval, it subtracts the number of points 
designated by the script writer from the maximum number of points. For 
example, if the maximum number of points was 100, the time interval is 5 
seconds, the points to subtract per interval is 10 points, and the viewer 
entered the correct answer in 32 seconds; then the viewer would be awarded 
40 points. 
If the script writer chooses Save Into 178, the script writer chooses the 
register (any one of SAVE1-SAVE7, to be discussed below) which will store 
the viewer's response. 
If the script writer chooses Threshold 180, the script writer enters the 
threshold goal which is the number of correct answers that a viewer must 
achieve, and the point value for reaching the threshold goal. 
Additionally, the script writer can enter text to be displayed by handheld 
32 informing the viewer whether the threshold was reached. 
If the script writer chooses In Range 182, the script writer enters the low 
limit of the range and the high limit of the range of acceptable answers. 
Additionally, the script writer enters the point value and a message for 
answering within the range of acceptable answers. 
Looking back at FIG. 3B, another option from the script menu is a table 
106. A table is text information, like a message. However, a message is 
displayed immediately and a table is stored in the memory of handheld 32. 
A viewer must use a key to get the information in a table. A key is a 
password learned by answering a correct question, watching a television 
program, reading a newspaper, or any other incentive an affiliate or 
advertiser might have. A viewer would enter the password into handheld 32 
which would trigger the display of the message from the table. The table 
is likely to include some type of valuable information. 
The script writer could chose score registration 108, which allows the 
script writer to send a message to the screen of handheld 32 indicating to 
the viewer that his or her score has met certain thresholds and that they 
should call operations 34 to register their score for a prize. The 
viewer's score may also be stored for long range storage in the memory of 
handheld 32. 
Script menu 66 also allows for branching 116, which is similar to branching 
in other types of computer programs. 
From script menu 66 the script writer can select mini-games 110, which 
allows the script writer to create questions, answers and messages for use 
in a mini-game (described above). 
When designing any of the scripits described above, the script writer has 
the option of entering in the frame number or other timing information to 
be used for transmitting the corresponding transaction to handheld 32. 
Once an interactive program is compiled, the object code created must be 
communicated to data insertion control 14. The means for transmitting 
object code to data insertion control 14 includes hand carrying by disk, 
using a computer network with appropriate software, communication over 
telephone lines, a wire, or authoring system 12 and data insertion control 
14 can share the same hardware. 
III. Data Insertion System 
In the preferred embodiment, data insertion control 14 is a windows 
application at least partially implemented using a high level programming 
language; for example, C. The windows application acts as control software 
for Insertion Card 20. The Insertion Card interface, however, is defined 
in terms of low level messages along with a framing structure and 
communications protocol. Thus, device driver 18 is needed to translate 
between these two environments. 
Device driver 18 requirements are defined in terms of required functions 
and general operations. There are four required functions that device 
driver 18 must perform. First, device driver 18 functions need to be made 
available to windows applications. This is accomplished by creating a 
library of linkable C functions. Second, interrupt handling routines must 
be installed to handle the transmit and receive interrupts associated with 
DMA transfers to and from Insertion Card 20. Third, DMA transfer to and 
from Insertion Card 20 must be initialized. Fourth, downloadable firmware 
must be sent to Insertion Card 20. 
FIG. 4 shows the hardware architecture for Insertion Card 20, which uses 
standard VBI insertion technology known in the art. It consists of a video 
processing circuitry, a video signal processor, a control processor, 
hardware failure detection circuitry and an IBM PC AT bus interface. 
Composite Video In 228 is first sent to hardware bypass 240. Should the 
hardware on Insertion Card 20 fail, Insertion Card 20 can be bypassed by 
properly switching hardware bypass 240 and 282, sending Composite Video In 
228 directly to hardware bypass 282 and exiting as Composite Video Out 
230. Normally, however, bypass 240 sends signal 228 to video clamp 242. 
Video processing circuitry is provided on Insertion Card 20 to slice data 
from the VBI and to insert data into the VBI. The data inserted into the 
VBI is the transaction data. Insertion Card 20 slices data from the VBI in 
order to monitor and validate data already existing in the VBI. For 
example, if a television program has been recorded on a videotape or other 
recording medium and there is data in the VBI, Insertion Card 20 can slice 
the data (e.g. read the data) in order to determine if the data is valid 
interactive data. If so, the Insertion Card could add a new valid stamp 
and/or time stamp (discussed below) to the date in order to ensure proper 
handling by handheld 32. 
Composite Video In 228 is accepted at the video input and referenced to a 
known DC signal at video clamp 242. The output of video clamp 242 is sent 
to three places. The first place, is the data slicing path where the 
output of video clamp 242 is sent to an Analog to Digital Converter 250 
and stored in FIFO 252. Video processor 268 then removes the VBI data from 
FIFO 252 in a non-real-time manner. 
The output of video clamp 242 is also presented to a sync separator 244 and 
sync generator 246 which together extract horizontal and vertical sync 
information used by video processor 268 for timing purposes. A 
synchronized composite black video can be created for testing purposes. 
The output of video clamp 242 is also AC coupled and sent to video mux 248. 
This path is used to allow the television program portion of the signal to 
pass through Insertion Card 20. 
Data is inserted into the VBI using both video processor 268 and control 
processor 266. Two processors are used on Insertion Card 20 to increase 
performance. Video processor 268 is used to process the data that is 
inserted into the VBI. Control processor 266 performs all other functions, 
including sending commands to video processor 268. Thus, RAM 270 can hold 
slightly more than one transaction of data, while RAM 254 can hold many 
transactions plus other data. In the preferred embodiment, the control 
processor 266 is a Motorola 68HC16 and the video processor is a Texas 
Instrument TMS 32052. Additionally, control processor 266 has ROM 256 for 
storing control software. 
In communication with control processor 266 is a DMA controller 258 which 
sends the proper handshaking and control signals to the IBM PC/AT bus 
interface 264. Data is sent from Insertion Card 20 on the transmit DMA 
channel from FIFO 262. Data is received from the receive DMA channel into 
FIFO 260. Via the DMA channel, insertion control 14 controls Insertion 
Card 20. Insertion control 14 determines when to send data, and what data 
to send. Insertion control 14 creates all the header information and data 
formatting (described below). Furthermore, insertion control 14 is 
responsible for the manipulating of data; for example, encrypting, 
interleaving, error codes and other data manipulation. 
When data insertion control 14 commands Insertion Card 20 to send data on 
the VBI, the data is received in FIFO 260 and sent to control processor 
266 which can add a valid stamp, and a time stamp based on Real Time Clock 
(RTC) 267. The data is then sent to video processor 268 where it is 
prepared for insertion into the VBI. Video processor 268 uses the sync 
information from sync separator 244 and sync generator 246 as timing 
information. The VBI data is then placed in FIFO 274. From FIFO 274 the 
data is digitized at A/D converter 276 and sent through low pass filter 
278, and on to video mux 248. 
The VBI is only a small portion of the video signal (see discussion below 
about VBI). Therefore, when data is being inserted into the VBI the video 
mux is selecting Composite Video for a majority of the time. During the 
portions of the Composite Video that constitute the VBI, video mux 248 
selects VBI data, which is the output of low pass filter 278. 
The control processor 266 is responsible for supporting downloadable code, 
video signal processor setup, all VBI commands and other general 
functions. The control processor 266 passes all received messages and 
formats all outgoing messages. It is also responsible for transaction 
framing/synchronization, FEC coding, time stamping and validation. 
IV. Data Transmission 
Data inserted by Insertion Card 20 must be in a format that conforms to 
existing television signals. Picture scan for a cathode ray tube 
television display is generally from left to right and top to bottom 
consisting of 525 horizontal lines per frame and 30 frames per second. 
Each frame is divided into two alternating fields: odd field and even 
field. Referring to FIG. 5, beginning at the upper left-hand corner of 
television screen 291 is line 22, followed by line 23, line 24, line 26, . 
. . line 261. This is the odd field. After line 261, the cathode ray beam 
then travels back to the top of the picture. The period of time while the 
beam is traveling back to the top of the picture is called the vertical 
blanking interval (or VBI). This is not an instantaneous bottom to top 
jump but actually requires the same length of time as 21 lines. These 
lines (the VBI) are numbered 262 to 282. The even field then begins with 
the second half of line 284, then line 285 . . . line 524. After line 524, 
the beam then travels back to the top of the picture during the vertical 
blanking interval. This vertical blanking interval is represented by lines 
1-21. 
FIG. 6 shows a time line 290 for the different lines of information in the 
video signal. The odd field vertical blanking interval is represented by 
290A which includes lines 1-21. Following VBI 290A is odd field 290B 
consisting of lines 22 through 261. After odd field 290B, the beam travels 
back to the top of screen 291, during which is the even VBI 290C, lines 
262 to 282. After even VBI 290C, the even field of data occurs 290D which 
includes lines 284 to 525. Each field of data (e.g. odd or even) and its 
accompanying VBI is 1/60th of a second. 
Odd vertical blanking interval 290A is broken out in FIG. 6 on line 294. 
The VBI includes vertical sync 294A which occupies lines 1-9, followed by 
the data lines 294B which occupy lines 10-21. The vertical sync 294A 
indicates the beginning of a vertical field, thus, signaling the need for 
the cathode ray beam to return scan to the upper left hand corner of the 
screen. Line 12 is broken out in more detail and shown as 300. 
Any conventional data format for a line of data is acceptable with the 
understanding that the data may be inserted on blank lines within the 
vertical blanking interval. One format for data transmitted within the VBI 
that is both well documented and considered to be reliable is the format 
chosen for closed captioning. This format transmits a horizontal 
synchronization pulse 306, a color burst signal 308, a clock run-in signal 
310, and a burst of data 302 which is preceded by a start bit 304. The 
data 302 includes fourteen bits of data and two parity bits. The horizonal 
sync pulse 306 is included in every line of data to signal the beginning 
of a line of data or, in other words, signaling a retrace by one line. 
Color burst 308 provides information needed to decode color. Each burst of 
data 302 is repeated at a rate of 16.67 milliseconds (as seen in FIG. 7). 
Data may be inserted on any of the lines of the VBI between line 10 and 
line 21. 
FIG. 8 shows the structure of the data that is sent on the VBI lines. Data 
insertion control 14 assembles the data into this format before inserting 
the data into the VBI. The data consists of a yellow signal 320, a 
synchronization pattern 322, header information 324, time stamp 326, 
transaction parameters 328, and transaction data 330. 
The yellow signal 320 is used to flag the beginning of a framed transaction 
and is used by Insertion Card 20 to avoid transaction collisions. It 
currently consists of two words of all 1's. 
The synchronization pattern 322 is used to synchronize the start of a 
transaction. The synchronization pattern 322 is currently defined as: 
11111001, 10101110, 00000110, 01010001, 10001010, 01100000, 01110101, 
10011111. 
Header 324 consists of a source address, destination address, affiliate 
number, VBI line number and transaction size. The source address is the 
address of the device that is generating the original data. The 
destination address is the address of the type of device that is receiving 
the data (e.g. handheld 32). 
Time stamp 326 is inserted into the interactive data by Insertion Card 20, 
at the direction of data insertion control 14, at the time of 
transmission. The time stamp, which identifies the time that the data was 
transmitted by the Insertion Card 20, is used to protect against cheating 
during an interactive program where prizes may be awarded. 
Parameters 328 include, but are not limited to, segment number, transaction 
number, game skill level, a validation stamp, time stamp enable, group 
number, unit number, mailbox number and other parameters associated with 
presenting transactions. Time stamp enable toggles the time stamp security 
system on and off. The validation stamp is used to distinguish valid 
interactive data from other data. 
In order to provide efficient and reliable transmission on the VBI, 
interactive data can be muxed, FEC coded, interleaved, combined, encrypted 
and error corrected. The data muxing function packs input items of various 
bit lengths into an integer number of bytes. Zero fill is used and items 
are combined most significant bit first. For example, if the source 
address is Aaaaaaaaaa, the mailbox number is Bbbbbbbbbb and the 
destination address is Cccc; then byte 1 could be Aaaaaaaa, byte 2 could 
be aaBbbbbb, and byte 3 could be bbbbCccc. 
The FEC coding function accepts an integer number of bytes and outputs an 
integer number of FEC codewords based on the FEC coding scheme being used. 
The preferred embodiment uses a rate of three-fourths code with a code 
word length of 32 bits. 
The interleaving function accepts an integer number of FEC code words and 
outputs an integer number of interleaved blocks. An interleaved block 
consists of 8 code words where 8 is the interleave factor. Zero fill is 
used if less than 8 code words are interleaved. For example, the following 
8 code words could be interleaved as follows: 
code word 1: AaaaaaaaBbbbbbbbCcccccccPppppppp 
code word 2: DdddddddEeeeeeeeFfffffffPppppppp 
code word 3: GgggggggHhhhhhhhliiiiiiiPppppppp 
code word 4: JjjjjjjjKkkkkkkkLIIIIIIIPppppppp 
code word 5: MmmmmmmmNnnnnnnnOoooooooPppppppp 
code word 6: QqqqqqqqRrrrrrrrSsssssssPppppppp 
code word 7: TtttttttUuuuuuuuVvvvvvvvPppppppp 
code word 8: WwwwwwwwXxxxxxxxYyyyyyyyPppppppp. 
After interleaving: 
code word 1: ADGJMQTWadgjmqtwadgjmqwadgjmqtw 
code word 2: adgjmqtwadgjmqtwadgjmqtwadgjmqtw 
code word 3: BEHKNRUXbehknruxbehknruxbehknrux 
code word 4: behknruxbehknruxbehknruxbehknrux 
code word 5: CFILOSVYcfilosvycfilosvycfilosvy 
code word 6: cfilosvycfilosvycfilosvycfilosvy 
code word 7: PPPPPPPPpppppppppppppppppppppppp 
code word 8: pppppppppppppppppppppppppppppppp 
The data combining function combines data by appending one input to 
another. The encryption function accepts an integer number of bytes and 
outputs an integer number of encrypted blocks. The encrypted block is 
defined by the specific encryption algorithm being used. Currently, an 
encryption block is 8 bytes. Zero fill is used. 
The CRC generation function accepts an integer number of bytes and 
calculates a 16-bit check word. A CRC algorithm is used to implement the 
following polynomial: x.sup.16 +x.sup.12 +x.sup.5 +1. Furthermore, 
Insertion Card 20 includes a select module (not shown) to determine on 
which VBI line to send the data. 
V. Settop device 
Data is recovered from the VBI, by settop device 28, at a sample rate of 
500,000 bits per second. However, this rate occurs for a short burst 
during the vertical blanking interval. A specific line of data only occurs 
every 16.7 milliseconds, thus, the data stream consists of 14 bits clocked 
at a high rate followed by 16.7 milliseconds of no data. As shown in FIG. 
7, the 14 bits are transmitted within 4.7 milliseconds. The purpose of 
settop device 28 is to recover this data transmitted during the VBI at a 
high data rate and, using infrared transmission, send that information to 
handheld 32 at a much slower data rate of 4,900 bits per second. This task 
can be accomplished generally using a buffer or memory device with 
different clock rates for input and output. 
FIG. 9 depicts a more detailed representation of settop device 28, which is 
similar to a conventional decoder for decoding VBI information used, for 
example, for closed caption applications. Settop device 28 includes a 
buffer 353 for receiving the video signal and a sync separator 354. This 
sync separator 354 extracts the synchronizing information (H Sync and V 
Sync: which are the horizontal sync and vertical sync discussed above) 
from the video signal and sends them to microprocessor 358. The stripped 
video signal which is the output of sync separator 354, labeled V-signal, 
is sent to data slicer 356. Data slicer 356 digitizes the signal and sends 
the digitized signal to microprocessor 358. Connected to microprocessor 
358 is ROM and RAM memory unit 360, which is used to store control code 
and data. 
Microprocessor 358 is connected to a clock (not shown). The clock includes 
a divider circuit so that two clock signals are available. The two clock 
signals have different frequencies which enable the settop device 28 to 
read data in at one speed and send data out at another speed. 
Microprocessor 358 is powered by power regulator 368. The output of 
microprocessor 358 goes to infrared transmitter 364. 
In operation, data is received as part of a video signal, sync information 
is stripped from the video signal and the transaction information is 
removed from the video signal, by microprocessor 358, using the sync 
information. Additionally, microprocessor 358 deinterleaves and decodes 
the data and stores the data in RAM 360. RAM 360 could be any memory 
device known in the art. The data is then clocked out of RAM 360 at a data 
rate of 4,900 bits per second where it is sent to IR transmitter 364 and 
transmitted to handheld 32. 
VI. Handheld 
Handheld 32, shown in FIG. 10, provides the means for participating in the 
interactive program. Handheld 32 receives a data stream from settop device 
28 and implements/presents the interactive program. The data stream 
received by handheld 32 includes commands and event specific data. 
The data stream is received first by an IR detector 380 which senses the 
infrared signal from settop device 28. The signal received by IR detector 
380 is sent to a 44 KHz demodulator 382 which removes the infrared carrier 
frequency, leaving a serial data stream. The serial data stream is sent to 
an 8-bit shift register 386 which converts the serial data stream to 
parallel data for microprocessor 388. The data sent to microprocessor 388 
is stored in RAM 390 until a full transaction is received. At that time, 
microprocessor 388, which communicates with real time clock (RTC) 389, 
builds a sequence of commands and data which are used to present the 
transaction. 
ROM and RAM 390 of microprocessor 388 contain a control program and a 
command interpreter for the commands sent on the VBI. The RAM portion 
stores the data and commands transmitted over the IR link. The preferred 
microprocessor 388 is an embedded processor, on an ASIC, similar to a 
Rockwell 65C02. In communication with microprocessor 388 is a secure 
microprocessor 392. The preferred secure microprocessor is Motorola 
68HC05SC27. Secured microprocessor 392 allows data to be stored in a 
tamper proof manner, unaccessible to unauthorized personnel. Handheld 32 
further includes a keyboard 394. A buzzer 396 is included to alert the 
viewer, for example, when the viewer's answer is correct or that handheld 
32 is awaiting a response. Handheld 32 further includes an LCD display 
398, which is a 4-line by 16-character display. LCD display 398, in the 
preferred embodiment, shall conform to the features of the Sharp LM24255 
(pre-programmed character generator ROM and 8-character generator RAM 
locations). To extend battery life, the LCD power should be controlled by 
an I/O bit from the microprocessor 388. Also connected to microprocessor 
388 is Infrared Transmitter 393 which communicates with dialer 33. 
Handheld 32 is powered by 6-volt battery 400 which is preferably 4 AA 
cells. There can be an additional lithium cell (not shown) that powers the 
ROM and RAM 390, and secure microprocessor 392 when loss of main power is 
detected since these must remain powered at all times. Main power is lost 
when the 6-volt battery 400 is drained below minimum working voltage or 
removed entirely. 
FIG. 11 shows an example of handheld 32. Case 420 is made from molded 
plastic of a strength and texture suitable for use by viewers in a 
household environment. Keypad 394 should be molded rubber with carbon 
contacts that make switch connections against a switch pattern on a 
printed circuit board. The buttons on keypad 394 could be marked with 
numbers and/or words. The words could include, but are not limited to 
"yes", "no", "true", "false", "poor", "fair", "average", "good", 
"excellent", "info" and "dialer". The "info" button is used to access 
tables. The "dialer" button is used to communicate with dialer 33. 0n the 
front 422 of handheld 32, is a window of red tinted plastic that filters 
visible light and receives infrared data. The IR receive circuitry will be 
mounted on a PC board behind this windows. 
As discussed above, handheld 32 receives all remote data from settop device 
28 via an infrared data link. The performance of this link should have a 
bit-error rate of less than 1-error for every 100,000 bits transmitted 
(random bit errors) when in the configuration shown in FIG. 12. In this 
configuration, handheld 32 should preferably be within 7.6 meters (25 
feet) from the transmitter of settop device 28 and anywhere within plus or 
minus 60.degree. of the central line of the transmitter. 
The features of an interactive program are implemented in part in software 
resident in handheld 32. This software performs two functions. The first 
function is to build a transaction from high level commands transmitted 
via the IR link. The second function is the execution/presentation of the 
transaction. During the time that a participant is responding to a given 
transaction, the next transaction is being received and made ready for the 
participant to process. Using this approach, the amount of information 
transmitted prior to a viewer being able to use handheld 32 is essentially 
transparent to the viewer compared to other interactive devices. 
Timed responses where the participant must react within a specific time 
interval can be controlled by either microprocessor 388 in conjunction 
with real time clock 389, or via a new transaction being sent and 
activated before the participant enters responses to the prior question. 
The interactive system can use encryption algorithms and keys as is known 
in the trade. Handheld 32 would thus store, for example, three keys at 
least one of which could be reprogrammed by a signal sent on the VBI. 
VII. Handheld Memory 
FIG. 13 shows the memory map for microprocessor 388 and secure 
microprocessor 392. With regard to microprocessor 388, memory location 
000-001F (450) is used to map the I/0 devices, e.g. keyboard, display, 
buzzer. Memory locations 0020-7FFF (452) is used as RAM to store 
programmer tables and other data. Locations D800-FFFF (454) is used as 
ROM. 
With respect to the secured microprocessor, memory location 000-001F (456) 
is used to map the I/0 devices. Locations 0020-00FF (458) is RAM. 
Locations 0530-1 OFF (460) is an EEPROM used to store programmer tables. 
Locations 4000-7FFFF (462) is ROM used to store control information. 
The interactive system stores data in handheld 32 in registers within 
programmer tables. Every affiliate has one or more assigned programmer 
tables so that handheld 32 knows where to store the information specific 
to that affiliate's interactive program. Additionally, handheld 32 has two 
universal registers used by all affiliates. One universal register is the 
Input Register, for temporarily storing viewer's answers to questions. For 
example, in a multiple choice question, if the viewer enters "4", the 
Input Register is loaded with a "4". The input register is automatically 
updated after each question. There is only one input register for each 
handheld 32. The second universal register is the Points Register, which 
stores the points earned for entering the correct response to a single 
question. For example, in a multiple choice question, the correct answer 
of "4" may earn 25 points. Therefore the value in Points Register would be 
25. 
FIG. 14 is a block diagram of a programmer table. There are fifteen 
registers per programmer table. Of the fifteen registers, eight have 
specific functions and seven are general. The eight specific registers are 
the Mailbox Register 470, Group Register 474, Unit Register 478, Score 
Register 482, Cume Register 484, Bank Register 500, Segment/Transaction 
Register 502 and Status Register 504. 
The Mailbox Register 470 stores the mailbox number. Affiliates can purchase 
(or be assigned) the exclusive rights to one or more programmer tables. 
The Group Register 474 stores the group number for the current 
transaction. The Unit Register 478 stores the unit number for the current 
transaction. The Segment/Transaction Register 502 stores the segment and 
transaction number for the current transaction. Status Register 504 holds 
the status for the current transaction, which includes the cheater bit. 
Initially, the cheater bit would be reset to zero. If, during the course 
of an interactive program, the viewer attempts to cheat, the cheater bit 
would be set to 1. Once the cheater bit is set to 1, the Cume Register 484 
is frozen. 
Score Register 482 stores the score for one program. For example, if the 
score for one game of a series is 225 points, the Score Register would 
have 225. Score Register 482 is automatically updated by the value in the 
Points Register after a correct answer is scored. Cume Register 484 stores 
cumulative scores for a series of programs as identified by the group 
number. The series may be one or more episodes. Using the example 
described above with respect to the score register, if the second game 
score is 275, the cume register could be 500, being the addition of game 
one (225) and game two (275) of the series. The cume register is 
automatically updated by the value in the Points Register 480 after every 
correct answer. 
Bank Register 500 stores the accumulated points earned within a mini-game, 
without updating the Score or Cume Registers. At the end of a mini-game, 
the script writer has the programming option to add Bank Register 500 to 
Score Register 483 and Cume Register 484, or to save the contents of Bank 
Register 500 for later use. For example, the script writer can use the 
value within Bank Register 500 for another mini-game without adding it to 
the viewer's Score and Cume Registers. Mailbox Register 470, Affiliate 
Register 472, Group Register 474, Unit Register 478, Points Register 480, 
Score Register 482, Cume Register 484, Bank Register 50, 
Segment/Transaction Register 502 and Status Register 504 are all updated 
by handheld 32. 
Registers Save 1-Save 7 (486, 488, 490, 492, 494, 496, 498), are general 
purpose registers used by the script writer to store data, for example, 
input assigned by the programmer with the Save Into response option. These 
registers can store viewer input for later use or text that a script 
writer wants to display in a message or question. A script writer may want 
to ask a question, store a viewer's answers in a register, and then use 
the stored answer for a branching condition. For example, the interactive 
program may have a question asking which team will win the game, San 
Francisco Giants or Atlanta Braves? The script writer could then choose 
the Save Into response option which causes, for example, a 1 to be stored 
in Save2 488 if the viewer selected the San Francisco Giants, or a 2 to be 
stored in Save2 488 if the viewer selected the Atlanta Braves. The script 
would include a branching instruction so that if Save2 contained a one, 
the message on handheld display 398 would be "The Giants are great 
hitters, watch for home runs!" Or, if Save2 contained a 2, the message on 
display 398 would be, "The Braves have great pitching, watch for a low 
scoring game!" 
For every question created in the authoring system for which points are 
awarded to viewers, handheld 32 usually updates at least four registers. 
The following example, using FIG. 15, demonstrates what is stored in 
various registers after asking a yes/no question. In row 510, a 25 point 
yes/no question is asked, "Do lions hibernate?" Handheld 32 displays the 
question and then waits for the viewer to enter an answer. The viewer's 
input will be stored in the Input Register. If the viewer enters the 
correct answer, 25 points will be loaded into the Points Register 480. For 
purposes of this example, this script is the second game of a series 
(since the first game ended with a score of 500, the Cume Register 484 is 
equal to the Score Register 482 plus 500) and the viewer's current score 
is 75 (thus, Score Register 482=75 and Cume Register=575). Row 512 occurs 
when the viewer enters a 1 representing a yes, which is the wrong answer. 
Handheld 32 displays the message, "No, lions live in warm climates and 
have no need to hibernate." Since the wrong answer was selected, no points 
are earned. Thus, the score and cume registers are not incremented. Row 
514 represents when the viewer enters a 2, representing a "no" which is 
the correct answer; therefore, handheld 32 will display the message, 
"Right! 25 pts. " The Points Register 480 is loaded with 25. The Score 
Register 482 is then updated by the addition of the Points Register 484. 
The equation is new Score Register value=old Score Register value plus 
Points Register. In this case, Score Register=75 pts.+25 pts.=100 pts. The 
Cume Register 484 is similarly updated by the addition of 25 pts. 
In summary, handheld 32 displays a question and then waits for the viewer 
to enter an answer. The answer is stored in the input register. Handheld 
32 then updates the other registers based upon the values stored in the 
input register. After the registers are updated, new transactions can be 
presented to the viewer. 
Table 1 shows a partial memory allocation for handheld 32. As described 
above, information is stored in the handheld 32 in programmer tables. 
There are three types of programmer tables: secured programmer tables, 
unsecured programmer tables and event specific programmer tables. 
Unsecured programmer tables have all of the information stored in RAM 390. 
Secured programmer tables have some of the information stored in RAM 390 
and some of the information stored in an EEPROM inside secure 
microprocessor 392. An event programmer table has some information stored 
in RAM 390 and some information stored in the EEPROM. Secured programmer 
tables are programmer tables with registers that cannot be accessed or 
tampered with by a viewer attempting to cheat. When interactive programs 
award prizes of value, a programmer may want to use a secured programmer 
table to prevent tampering or cheating. If the game is played without any 
incentive for cheating, for example no prizes, an unsecured programmer 
table could be used. 
As described above, programmer tables are assigned to affiliates. For 
example, they could be sold on a per programmer table basis. Thus, a given 
affiliate may buy five or ten programmer tables to use for all of its 
interactive programs. However, there may be an occasion where an affiliate 
needs to use to a programmer table for a particular interactive program 
but has no programmer tables available in its own set of prepurchased 
tables. Or, a first time viewer may want to try an interactive program on 
an incremental basis. Thus, an affiliate can buy an event programmer table 
which is a programmer table available only for one particular event. The 
most useful function for event specific programmer tables is in 
conjunction with pay-per-play events. For example, a viewer might be given 
the opportunity to buy the right to participate in a pay-per-play 
interactive program in conjunction with a pay-per-view boxing match. In 
this situation, the viewer would order the pay-per-play event and receive 
an access code to activate the specific event programmer table, which 
enables the viewer to participate in the pay-per-play interactive program. 
Table 1 shows the preferred maximum number and allocation of the three 
types of programmer tables with respect to RAM 390 and the EEPROM inside 
secure microprocessor 392. The column labeled "EE Bytes" represents bytes 
of data stored in the EEPROM of secured microprocessor 392. The column 
labeled "RAM Bytes" represents bytes of data stored in RAM 390. In the 
preferred embodiment, there are 204 secured programmer tables, there are 
182 unsecured programmer tables and 20 event tables. 
For example, Table 1 shows that there are 204 secured programmer tables, 
with each programmer table having a Group Register which is 10 bits wide. 
Therefore, 255 bytes of the EEPROM in secured microprocessor 392 are used 
for secured programmer table Group Registers. 
TABLE 1 
______________________________________ 
RAM EE 
Purpose Quantity Size Bytes Bytes 
______________________________________ 
Secured Tables: 
Group # 204 10 bits 255 
Unit # 204 4 bits 102 
Mailbox # 204 14 bits 357 
Score 204 3 Bytes 612 
Cume 204 3 Bytes 612 
Save 1-7 204 21 Bytes 4284 
Bank 204 3 Bytes 612 
Status 204 1 Byte 204 
Seg/Trans 204 3 Bytes 612 
Unsecured Tables: 
Group # 182 10 bits 228 
Unit # 182 4 bits 91 
Mailbox # 182 14 bits 319 
Score 182 3 Bytes 546 
Cume 182 3 Bytes 546 
Save 1-7 182 21 Bytes 3822 
Bank 182 3 Bytes 546 
Status 182 1 Byte 182 
Seg/Trans 182 3 Bytes 546 
Event Tables: 
Group # 20 10 bits 25 
Unit # 20 4 bit 10 
Mailbox # 20 14 bits 35 
Score 20 3 Bytes 60 
Cume 20 3 Bytes 60 
Save 1-7 20 21 Bytes 420 
Bank 20 3 Bytes 60 
Status 20 1 Byte 20 
SegfTrans 20 3 Bytes 60 
______________________________________ 
VIII. Handheld Sequencing 
Handheld 32 uses the mailbox number, group number, unit number, segment 
number, transaction number, time stamp enable and cheater bit in order to 
ensure that the viewer is playing the transactions in the proper sequence. 
Sequence is important for two reasons. First, monitoring the sequence of 
transactions can be used to detect cheating. Second, if for any reason a 
transaction is missed by handheld 32 (e.g., data loss or a viewer was 
surfing or grazing) it is desired that handheld 32 not continue processing 
transactions in that segment. For example, if the question in a sequence 
of question-answer-scoring is missed, handheld 32 should not wait for the 
response because the viewer does not know that handheld 32 is waiting for 
an answer, nor would there be an answer to score. Handheld 32 should 
remain idle until the start of the next sequence. 
The following examples help describe how handheld 32 sequences through an 
interactive program and updates the appropriate registers. Most of the 
examples have two columns followed by an explanation. The left column is 
certain data associated with a new transaction as compared to the previous 
transaction. The right column shows the effect that the data in the left 
column has on a programmer table. 
EXAMPLE 1 
______________________________________ 
Mailbox # Same Score = Updated 
Group # Same Cume = Updated 
Unit # Same Sav1--Sav7 = Updated 
CB = Same 
______________________________________ 
In this first example, the transaction data is referencing the same Mailbox 
Number, Affiliate Number, Group Number, and Unit Number as the previous 
transaction. Therefore, this transaction will use the same programmer 
table as the previous transaction. The current transaction is the next 
transaction in the same game as the previous transaction. Thus, the 
programmer table is maintained and updated accordingly. 
EXAMPLE 2 
______________________________________ 
Mailbox # Different 
Group # Don't Care 
Unit # Don't Care 
Segment # Don't Care 
Transaction # Don't Care 
Time Stamp Enable Don't Care 
______________________________________ 
This transaction has a different Mailbox Number than the previous 
transaction; therefore, handheld 32 uses a different programmer table. 
EXAMPLE 3 
______________________________________ 
Mailbox # Same Score = 0 
Group # Different Cume = 0 
Unit # Same Sav1-Sav7 = 0 
CB = 0 
______________________________________ 
In this situation, handheld 32 is using the same programmer table; however, 
a new interactive program (or series) is starting due to the new group 
number. Since the new transaction is part of a new series, the Score, 
Cume, Point and Save Registers are reset to zero and then updated with the 
scores from the new transaction. 
EXAMPLE 4 
______________________________________ 
Mailbox # Same Score = 0 
Group # Different Cume = 0 
Unit # Different Sav1-Sav7 = 0 
CB = 0 
______________________________________ 
As in the previous example, a new program or series is starting that uses 
the same programmer table as the previous transaction. 
EXAMPLE 5 
______________________________________ 
Mailbox # Same Score = 0 
Group # Same Cume = Updated 
Unit # Different Sav1-Sav7 = Updated 
CB = Same 
______________________________________ 
This is an example where the new transaction is using the same programmer 
table and is part of same series as the previous transaction, but has a 
different unit number. Thus, the new transaction is the next game in the 
series. For example, it may be a new game in the World Series. Thus, 
handheld 32 should zero out the Points and Score Registers but maintain 
the Cume Register. 
EXAMPLE 6 
______________________________________ 
Mailbox # Same Score = Same 
Group # Same Cume = Same 
Unit # Same Sav1-Sav7 = Same 
Segment# Backward Sequence 
CB = Same 
Transaction # 
! = 1 
Time Stamp Enable 
True 
______________________________________ 
In this example, the segment number has changed but in backwards sequence. 
For example, handheld 32 was processing segment 7; however, the new 
transaction is from segment 5. Since the transaction number is not equal 
to 1, handheld 32 is receiving this transaction in the middle of a 
sequence. This may be an example of a viewer who taped a portion of an 
interactive program and is attempting to replay part of the program. Thus, 
handheld 32 will ignore this transaction, and wait for the beginning of 
the next sequence. Ignoring the transaction includes not presenting the 
transaction and not updating any programmer tables. Therefore, the 
programmer table will not be updated with the new sequence number; thus, 
the next transaction received by handheld 32 is also likely to be out of 
sequence. The next transaction with a transaction number of 1 is likely to 
be analogous to Example 8. 
EXAMPLE 7 
______________________________________ 
Mailbox # Same Cume = Frozen 
Group # Same Score = 0 
Unit # Same Sav1-Sav7 = Updated 
Segment # Backward Sequence 
CB = 1 
Transaction # 
1 
Time Stamp 
True 
Enable 
______________________________________ 
This situation is similar to the previous example except the transaction 
number is 1. Therefore, handheld 32 would conclude that the transaction is 
at the beginning of a segment and the segment is out of order. Handheld 32 
assumes that the viewer is cheating by taping the interactive program and 
replaying it. Therefore, the cheater bit is set to 1 which freezes the 
Cume Register 484. Points Register 480 and Score Register 482 are reset to 
zero. The transaction is played without effecting the cumulative score. 
EXAMPLE 8 
______________________________________ 
Mailbox # Same Score = 0 
Group # Same Cume = 0 
Unit # Same Sav1-Sav7 = 0 
Segment # Backward Sequence 
CB = 0 
Transaction # 
1 
Time Stamp Enable 
False 
______________________________________ 
This situation is the same as the previous situation, however, the time 
stamp enable is false. Therefore, even though the viewer is playing out of 
sequence, Cume Register 484 will not be frozen. Rather, handheld 32 resets 
the registers and allows the viewer to restart the game. This situation 
would arise in a children's video or another interactive program where 
prizes are not awarded and/or cheating is not relevant. 
EXAMPLE 9 
______________________________________ 
Mailbox # Same Score = Same 
Group # Same Cume = Same 
Unit # Same Sav1-Sav7 = Same 
Segment # Fwd. out of seq. 
CB = Same 
Transaction # 
! = 1 
Time Stamp Enable 
True 
______________________________________ 
In this situation, the segment number is out of order, and the new 
transaction is not the first transaction of the segment. Therefore, the 
viewer is trying to play a segment by entering in the middle of the 
segment. This transaction may be a response; however, no question was 
queried to the viewer. Handheld 32 does not present this transaction to 
the viewer. Handheld 32 will remain idle (from the viewer's point of view) 
until the beginning of the next segment, where handheld 32 will start 
presenting transactions to the viewer (see Example 11). This may be the 
situation where the viewer was initially participating in the interactive 
game, but temporarily stopped. Perhaps the viewer momentarily changed 
television channels or stepped away from the television viewing area (e.g. 
bathroom break). Although the viewer can continue participating, the 
viewer loses out by losing the potential scoring from the missed 
transactions. 
EXAMPLE 10 
______________________________________ 
Mailbox # Same Score = Updated 
Group # Same Cume = Updated 
Unit # Same Sav1-Sav7 = Updated 
Segment # Fwd. out of seq. 
CB = Same 
Transaction # 
1 
Time Stamp Enable 
True 
______________________________________ 
This situation is similar to Example 10 except that the transaction number 
is 1. Therefore, the viewer has missed some transactions and is now at the 
beginning of a new segment. Since the transaction is at the beginning of a 
segment, handheld 32 allows the viewer to play the transaction and, 
appropriately updates the Score and Cume Registers. As in Example 10, the 
viewer does not receive any scoring from the missed transactions. 
EXAMPLE 11 
______________________________________ 
Mailbox # Same Score = Updated 
Group # Same Cume = Updated 
Unit # Same Sav1-Sav7 = Updated 
Segment # Same CB = Same 
Transaction # 
In sequence 
Time Stamp Enable 
True or False 
______________________________________ 
This situation is the norm. The viewer is playing the next transaction in 
the same segment and all the registers are appropriately updated. 
EXAMPLE 12 
______________________________________ 
Mailbox # Same Score = Same 
Group # Same Cume = Same 
Unit # Same Sav1-Sav7 = Same 
Segment # Same CB = Same 
Transaction # 
Bck. seq. ! = 1 
Time Stamp Enable 
True 
______________________________________ 
In this situation, the transaction has same segment number but a lower 
transaction number which is not equal to 1. For example, the previous 
transaction had a transaction number of 6; however, the current 
transaction has a transaction number of 4. The viewer most likely 
attempted to replay a taped transaction. The transaction is ignored. 
Handheld 32 may start presenting transactions when it receives a 
transaction with a transaction number of one. Until that time, the 
registers will not be updated. 
EXAMPLE 13 
______________________________________ 
Mailbox # Same Score = 0 
Group # Same Cume = Frozen 
Unit # Same Sav1-Sav7 = Updated 
Segment # Same CB = 1 
Transaction # 
Bck. seq. = 1 
Time Stamp Enable 
True 
______________________________________ 
This is the same situation as the previous example except that when the 
viewer rewound the tape (assuming the viewer videotaped), the tape was 
rewound to the beginning of the sequence. Thus, the transaction number is 
1. Handheld 32 assumes the viewer is trying to cheat; therefore, handheld 
32 resets the Score and Points Registers, freezes the Cume Register and 
sets the cheater bit to 1. The viewer can continue to play the interactive 
program and update the Score Register, but the viewer's score does not 
count toward a prize. Because the Cheater Bit (CB) is set to one, the Cume 
Register is frozen and the viewer would not receive a message to register 
the viewer's score with operations 34. 
EXAMPLE 14 
______________________________________ 
Mailbox # Same Score = 0 
Group # Same Cume = 0 
Unit # Same Sav1-Sav7 = 0 
Segment # Same CB = 0 
Transaction # Bck. seq. = 1 
Time Stamp Enable 
False 
______________________________________ 
This situation is the same as the situation in example 12, however time 
stamp enable is set to false. Thus, handheld 32 does not care that the 
viewer may be cheating. A new game is started. 
EXAMPLE 15 
______________________________________ 
Mailbox # Same Score = Same 
Group # Same Cume = Same 
Unit # Same Sav1-Sav7 = Same 
Segment # Same CB = Same 
Transaction # 
Fwd. out of seq. 
Time Stamp Enable 
True or False 
______________________________________ 
In this situation the viewer is playing the interactive program out of 
sequence. The viewer may have taped and is jumping ahead, the viewer may 
have switched channels (surfed) and now has come back, or the viewer may 
have momentarily left the television viewing area and missed a 
transaction. Since handheld 32 knows it is playing a transaction out of 
sequence within the same segment, the handheld merely ignores the 
transaction and waits for a new transaction with a transaction number of 
1. The registers are not updated. 
EXAMPLE 16 
______________________________________ 
Mailbox # Same Score = Same 
Group # Same Cume = Same 
Unit # Same Sav1-Sav7 = Same 
Segment # Same CB = 1 
Transaction # Same 
Time Stamp Enable 
True or False 
______________________________________ 
In this situation the viewer is attempting to replay the exact same 
transaction again. Handheld 32 simply ignores the transaction. The cheater 
bit is set to one because the viewer is attempting to cheat. 
It follows from the above description that, even with interleaved games and 
the viewer's entering and leaving the interactive program at various 
times, the viewer's reactions and answers to all games in which the viewer 
participates are stored in some form by handheld 32 and later can be 
reported to a central processing station (operations 34). 
The interactive system discussed above is used to demonstrate one platform 
for using the time stamping security system described below. It is 
contemplated that the time stamping security system of the present system 
could be used with various other types of systems. 
IX. Time Stamps 
Time stamp 326 is inserted into the interactive data by the VBI card 20 
using the method depicted in FIG. 16. The first step is to design a 
transaction or segment (617). The second step is to insert a time stamp 
into the transaction data (618). Alternatively, the time stamp could be 
inserted once for each segment. Time stamp 326 should represent the 
current date/time that the time stamp 114 is inserted into the VBI. The 
third step includes inserting the interactive data into the VBI (619). It 
is also contemplated that time stamp 326 could be inserted directly into 
existing VBI data in a television signal. Finally, the video and data are 
transmitted to the remote locations (620). 
The system for preventing cheating is based on relative times. Handheld 32 
receives interactive data having a time stamp based on a real time clock 
267. Microprocessor 388 of handheld 32 compares time stamp 326 to handheld 
clock 389 to determine a difference (or "delta"). The "deltas" for two 
successive transactions are then compared in order to determine which of 
the transactions (or segments) are delayed with respect to the other. The 
score from the transactions that are not delayed are added to the 
cumulative score. After the game is complete, or at some other stopping 
point, a viewer's cumulative score, along with a "delta" and a current 
reading of handheld clock 389, are registered with operations 34. The 
difference between the operations clock (which must be synchronized to 
real time clock 267 in VBI card 20) and handheld clock 389 is compared to 
the transmitted delta in order to verify the cumulative score. 
A more detailed discussion of the method for using time stamps to prevent 
cheating will be discussed in reference to the flowchart shown in FIGS. 
17-19. First, handheld 32 would receive the first transaction (622). Clock 
389 in handheld 32 is read at the time the transaction is received (624). 
Time stamp 326 (TS) contained in the transaction data is compared to 
handheld clock 389 ("HHCLK") (626). A "delta" (.DELTA.) is calculated, the 
"delta" being equal to the time read from handheld clock 389 minus the 
time stamp (626). The "delta" is then stored (628), this is called a 
"stored delta" (S.DELTA.). The "stored delta" may be updated as different 
transactions are processed. The transaction is then presented to the 
viewer (630). Presenting the transaction may (but is not limited to or 
required to) include presenting a question, waiting for or receiving an 
answer, displaying the correct answer or scoring a response. 
The second transaction is then received (634) (see FIG. 18). Handheld clock 
389 is read at the time the second transaction is received (636). The 
"delta" for the second transaction is also calculated (638) and the second 
transaction is presented to the viewer (640). At this point, handheld 32 
calculates a "discrepancy" (642). The "discrepancy" (DSC) is equal to the 
"delta" of the current transaction, which in this case is the second 
transaction, minus the "stored delta." 
The "discrepancy" indicates whether one of the transactions is delayed with 
respect to the other transaction. A non-zero "discrepancy" would indicate 
a difference in the delay of the two transactions. A "discrepancy" greater 
than zero would indicated that the second transaction was delayed as 
compared to the first transaction. A "discrepancy" less than zero would 
indicate that the first transaction was delayed as compared to the second. 
If the "discrepancy" is zero, then the transactions were broadcast with 
the same delay. 
Additionally, handheld 32 can be designed to allow for clock drift. For 
example, although the first transaction and the second transaction could 
be sent with the exact same delay, because clock 389 could drift the 
"deltas" may be slightly different. Thus, the "discrepancy" is compared to 
an allowable amount of drift between transactions, rather than zero. If 
this time drift constant (TDI) is, for example, 3 seconds, the 
transactions would be accepted as having no difference in delay time if 
the "discrepancy" was less than 3 seconds. 
If the "discrepancy" was greater than the first time drift constant (TD1), 
for example, if we allowed 3 seconds as our time drift constant and the 
"discrepancy" was 4 seconds, then handheld 32 could conclude that the 
second transaction was delayed as compared to the first transaction (650). 
Since the second transaction was delayed, the cumulative game score should 
not be updated with the score from the second transaction. Thus, the Cume 
Register 484 would be frozen. 
If the absolute value of the "discrepancy" was less than the first time 
drift constant then neither transaction was delayed as compared to the 
other and the score from the second transaction could be added to the 
cumulative score (648). If the "discrepancy" is less than the negative of 
the first time drift constant, handheld 32 would conclude that the first 
transaction was delayed as compared to the second transaction (152). For 
example, if the first time drift constant was 3 seconds and the 
"discrepancy" was negative 5, meaning that the stored delta was 5 seconds 
greater than the delta of the second transaction, handheld 32 would 
conclude that everything before the second transaction was delayed. This 
conclusion is made because the "stored delta" represents the delta of the 
last "live" transaction. Accordingly, the Cume Register 484 and Score 
Register 482 would be reset to zero and updated as per the second 
transaction. 
If handheld 32 concluded that the second transaction was delayed as 
compared to the first transaction, then the "stored delta" remains the 
"delta" of the first transaction. If both transactions have the same 
delay, the "stored delta" is updated to equal the "delta" of the second 
transaction. If the first transaction was determined to be delayed with 
respect to the second transaction, then the "stored delta" is updated to 
equal the "delta" for the second transaction. 
As discussed above with respect to FIG. 7, parameters 328 include a time 
stamp enable (TSE). When TSE is zero, the handheld ignores the time stamp 
and does not compute "delta". 
As discussed above, handheld 32 sets the cheater bit (CB) to one if either 
transaction was delayed as compared to the other (e.g., 
"discrepancy".noteq.0). Once CB is set to 1, the Cume Register 484 would 
be frozen. That is, once a user tries to play a delayed transaction, the 
user will be penalized for the entire series by not allowing the user to 
accumulate any more points regardless of whether the user is playing live 
or delayed transactions. 
One alternative embodiment includes a handheld without a cheater bit. 
Rather than freezing the Cume Register (or the Score Register), the Cume 
Register will only be updated with non-taped transactions. For example, if 
the first transaction was delayed as compared to the second transaction, 
before scoring the second transaction, the Cume Register will be reset to 
zero and then updated with the score from the second transaction. The Cume 
register will continue to be updated with scores from future non-taped 
transactions. 
If the second transaction was delayed as compared to the first transaction, 
the Cume Register will be updated with the score from the first 
transaction but not the second transaction. Additionally, the Cume 
Register will be updated with the score of any future transaction which is 
not delayed as compared to the first transaction. 
If neither transaction was delayed as compared to the other, the Cume 
register will reflect the scores from both transactions. As discussed 
below, at the end of the game the cumulative score will then be checked to 
determine if the entire interactive program was inappropriately delayed. 
This alternative embodiment allows a viewer who is participating in a 
series to "replay" part of a game without affecting the cumulative score. 
Or, if a viewer missed part of an interactive program, the viewer can play 
the missed portion of the program (if the viewer had the program 
videotaped) without affecting the cumulative score. 
At the end of the game, in the preferred embodiment and the alternative 
embodiment, handheld 32 will display the viewer's cumulative score, the 
handheld clock time, the "stored delta", and a message directing the 
viewer to register the viewer's score. The viewer would then register the 
cumulative score, handheld clock time and "stored delta", by any of the 
means discussed above (654). Instead of displaying the cumulative score, 
the handheld clock time and the stored delta, handheld 32 can display a 
code word which is some encrypted combination of the three numbers. 
Operations would compute a "time difference" (TDIFF). The "time difference" 
is the difference between the operations clock and the handheld clock 389 
(656). "Time offset" (TO) is then calculated to be equal to the difference 
between "time difference" and the transmitted "stored delta" (658). "Time 
difference" should equal the "stored delta" if the score was generated by 
a live feed (660). Thus, if "time offset" is equal to zero, then the 
transactions were presented from a live feed and the cumulative score is 
valid (664). If time offset is not zero, then the entire set of 
transactions are considered delayed and the score is not valid (662). 
As discussed above, the clock 389 on handheld 32 could drift. Thus, the 
score may be valid even though "time offset" is not quite zero, but close 
to zero. To compensate for this, "time offset" is compared to a second 
time drift constant (TD2). If the absolute value of "time offset" is less 
than the second time drift constant, the score is valid; else, the score 
is not valid. Furthermore, comparing "time offset" to a time drift 
constant, rather than to zero, allows for transmission time delays. 
Several examples will be given to illustrate various scenarios using the 
above-described security system. Each example uses a two-segment 
interactive program, each segment having one transaction. In each case, 
the cumulative score is registered after the game is played. 
X. Examples 
A. EXAMPLE 1: Normal Operation, Handheld Clock 389 Synchronized 
In this example, the viewer simply plays the game as it is broadcast and 
then registers the cumulative score. It is assumed that the internal 
handheld clock 389 is perfectly synchronized to real time clock 267 on VBI 
card 2. The first transaction has a time stamp of 10:05:30. Handheld clock 
389 also has this time. The difference "delta", between these times is 
zero so the handheld 32 saves zero as the "stored delta". 
The second transaction has a time stamp 10:10:45. The handheld clock 389 
also has this time. The delta time is zero. This new "delta" is compared 
to the old "stored delta" to produce a "discrepancy." Since the 
discrepancy is zero, there is no difference in transaction delay and 
transaction processing continues as usual. 
The score is registered at 10:15:00. At this time, the handheld clock time 
and "stored delta" are registered with the operator. The operator compares 
the operations clock with the handheld clock 389. The difference, "time 
difference," which is zero in this example, should match the "stored 
delta" if the score was generated from a live feed. Since time offset is 
zero in this case, the cumulative score is valid. 
B. Example 2: Normal Operation, Handheld Clock 78 Not Synchronized 
In this example, assume that the handheld clock 389 has drifted by 20 
seconds. The first transaction is received with a time stamp of 10:05:30. 
Handheld clock 389 reads 10:05:10. The difference, "delta", is -00:00:20 
which is saved as the "stored delta". 
The second transaction received has a time stamp of 10:10:45. Handheld 
clock 389 reads 10:10:25. The new "delta" is -00:00:20 which agrees 
exactly with the old "delta" to produce a time "discrepancy" of 00:00:00. 
This indicates no difference in the delay of the two transactions. 
The cumulative score is registered at 12:15:00. At this time, the handheld 
clock 389 and "stored delta" are passed to the operator. The operator 
compares the operations clock with the handheld clock 389. "Time 
difference" is 00:00:20. Thus, "time offset" is zero indicating a valid 
cumulative score. This illustrates the fact that the handheld does not 
have to be synchronized. 
C. Example 3: Taped Delay Operation 
In this example, the first transaction has a time stamp of 10:05:30. 
Handheld clock 389 has 11:05:30 producing a "delta" of 01:00:00. 
The second transaction has a time stamp of 10:10:45. The new "delta" is 
01:00:00 creating a "discrepancy" of 00:00:00. This indicates no 
difference in the delay of the two transactions. 
The cumulative score is registered at 12:15:00. The operator compares the 
operations clock (12:15:00) with the handheld clock 389 (12:15:00) which 
yields 00:00:00 (the two clocks are synchronized). "Time offset" is 
calculated and found to be non-zero (-01:00:00). This indicates that the 
cumulative score was generated from a delayed signal of one hour, and the 
cumulative score is invalid. 
D. Example 4: Taped Delay Operation With Varying Delays 
In this next case, we will examine two delayed transactions with different 
delays. The first transaction with a time stamp of 09:05:30 is received 
one hour late at 10:05:30. Handheld clock 389 has 10:05:30 yielding a new 
"delta" of 01:00.00. 
The second transaction with a time stamp of 09:40:45 is received 30 minutes 
late at 10:10:45. The new "delta" is 00:30:00 creating a "discrepancy" of 
-00:30:00. This indicates a difference in the delay of the two 
transactions. Since the "discrepancy" is negative, the first transaction 
was received delayed relative to the second transaction. In other words, 
the first transaction is assumed to be delayed and the second transaction 
is assumed to be live (this, of course, is not the case since both 
transactions were delayed). "Stored delta" is taken from the so called 
live transaction and is set to 00:30:00. 
The score is registered at 12:15:00. The operator compares the operations 
clock (12:15:00) with the handheld clock 389 (12:15:00) which yields a 
"time difference" of 00:00:00. "Time offset" is calculated and found to be 
non-zero (-00:30:00). This indicates that the score was generated from a 
delayed signal of 30 minutes and the score is invalid. 
E. Example 5: Drifting Handheld Clock Operation 
The first transaction with a time stamp at 10:05:30. The handheld clock has 
10:05:30 yielding a new "delta" of 00:00:00. 
The second transaction with a time stamp of 10:10:45. The handheld clock 
has 10:10:44 yielding a new "delta" of -00:00:01 (the handheld clock has 
drifted by one second). The "discrepancy" is -00:00:01. Since we realize 
that the handheld clock will drift and we wish to tolerate a certain 
amount of drift, the "discrepancy" is not compared to zero. Instead, the 
absolute value of "discrepancy" is compared to the allowable amount of 
drift between transactions. If this allowable amount is, say, three 
seconds, the transaction would be accepted as having no difference in 
delay time. The new "stored delta" would be the "delta" from the current 
transaction (-00:00:01). 
The score is registered at 12:15:00. The operator compares the operations 
clock (12:15:00) with handheld clock 389 (12:14:55) which yields a "time 
difference" of -00:00:05. "Time offset" is calculated and found to be 
non-zero (-00:00:04). As above, we wish to tolerate a certain amount of 
handheld clock drift. Instead of comparing "time offset" to zero, we 
compare the absolute value of "time offset" to the allowable amount of 
drift. If this allowable drift is, say, 10 seconds, the "time offset" 
would be less than the time drift constant and the score is valid. 
Allowable amounts of drift could be determined not in units of seconds, 
but instead in units of parts per million (PPM). 
Although the previous description of the security system is described with 
respect to an interactive television system, the security system could 
have other applications. For example, the security system could be used 
with pay-per-view TV. The pay-per-view operator would list the events that 
could be subscribed to and the viewer could select which events they want, 
and only pay for the selected events. The viewer may choose a certain 
movie to be televised in the viewers's home. The viewer could record the 
movie using a VCR, or other recording or storage method, and view the 
movie as often as desired without paying additional fees. It is 
contemplated that the security method described in this application can be 
used to prevent the viewer from replaying the movie without paying 
additional fees by checking embedded time stamps. 
Other objects, aspects and advantages of the invention can be obtained from 
a view of the claims and the appended figures. 
It is to be understood that other embodiments of the present invention can 
be constructed and be within the spirit and scope of the present 
invention.