CN101534429B - Pirate Tracking Method and System - Google Patents

Abstract

The invention provides a pirate tracking method and a system thereof. The method adopts a combination elimination technique to determine the pirate from end users according to the detected illicit diffused code word. Using the method to track the pirates solves the existing bottleneck in tracking the pirate, namely the problem of restricts by the cost and technology realization brought by the number of user groups and the increase in the number of user groups. Moreover, the tracking efficiency is high and the benefits of the operators are protected.

Description

Pirate tracking method and system

technical field

The invention relates to the digital TV pirate tracking technology, in particular to a pirate tracking method and system. the

Background technique

With the development of Internet video technology and digital TV, as well as the richness of media content, the digital TV operation mode in which users pay to order their favorite video programs has emerged and gradually popularized, and video content providers are more inclined to use digital TV systems to release programme. In the digital TV system, video programs are broadcasted to all users after being encrypted. Each user has a decryption device at the receiving end. If a user subscribes to a certain program, the corresponding decryption device can recover the plaintext of the program. If If no program is subscribed, the decryption device cannot decrypt the program, and the program package is discarded. the

However, user piracy has become a major problem restricting the development of the digital TV industry. Piracy in the broadcasting mode of digital TV is mainly that pirates obtain program decryption keys by attacking decryption devices and illegally distribute them. The problem of user piracy will become an important problem that plagues digital TV program operators. If this problem cannot be effectively solved, the mode of paying to watch programs may be seriously affected. Therefore, Traitor Tracing exists for anti-piracy. in,

FIG. 1 is a schematic diagram of dynamic traitor tracking in the related art. Among them, the feedback information from pirates is used to shorten the time required to track down traitors. the

As shown in Figure 1, the total number of end users in the system is n, and the publisher divides users into groups and distributes the same codewords to each group. Different user groups distribute different codewords. Several colluding pirate users will choose one of the codewords they get to carry out illegal diffusion. The publisher monitors the illegally diffused codewords, infers which user group the codewords come from, and then infers pirated users by combining the previous codeword leak information and group information. If it cannot be judged, adjust the grouping of users based on this information, redistribute codewords and monitor until the collected information is sufficient to deduce the pirate. the

The above-mentioned "codeword" is an abstract concept, and the codeword can be different decryption keys for the same program, or a media file embedded with different fingerprint information. the

In related technologies, when judging pirates, a binary tree (or multi-tree) search method can be used to determine pirate users. Only when the number of user groups is greater than the number of colluding users can a deterministic tracking strategy be constructed. Taking the case where the relationship between the maximum number of user groups r and the upper bound p of the number of pirated users satisfies r=2p+1 as an example, this tracking strategy uses one user group I to store possible innocent users, and uses the remaining 2p user groups to store possible innocent users. There are p pirated users, each user group pair {Li, Ri} has at least one pirated user. If the monitored illegal diffusion codeword is the codeword assigned to I, then I is divided into two parts Li and Ri with the same number of users, and I is empty; if the monitored codeword is assigned to Li, then Merge Ri with I, and divide Li into two parts, Li and Ri; if the detected codeword comes from Ri, combine Li with I, and divide Ri into two parts, Li and Ri. After each step, the number of users in a user group will be halved until the codeword assigned to a user group containing only one user is detected, then a pirated user will be tracked down and the user will be disconnected from the system , and continue the above steps until all pirated users are traced. the

In the above dynamic tracking strategy of r=2p+1, the number of groups in the first few steps of the search process is usually much smaller than the maximum number of groups r. In practical applications, due to the complexity of multi-decryption key system design or the limitation of transmission bandwidth, the maximum number of packets is often limited, or in other words, a higher price must be paid to increase the maximum number of packets. Therefore, the above dynamic tracking strategy The established system conditions cannot be fully utilized, resulting in affected search efficiency. the

Contents of the invention

The object of the present invention is to provide a method for tracking pirates, the method is to use the combined elimination method to track pirates, solve the existing bottleneck problem of pirates tracking, that is, the number of user groups and the increase in the number of user groups brought Cost, technology implementation and other conditions are constrained, and the tracking efficiency is high, safeguarding the interests of operators. the

The purpose of the present invention is also to provide a pirate tracking system, through which the existing bottleneck problem of pirate tracking is solved, the tracking efficiency is high, and the interests of operators are maintained. the

In order to achieve the above object, the present invention provides a method for tracking pirates. The method includes: determining the pirates among the end users according to the monitored illegally diffused codewords and using a combination exclusion method, wherein the method is based on the codewords, using a combination of Elimination methods to identify pirates among end users include:

Step 1, grouping the current terminal users, and assigning different codewords to each group;

Step 2, monitoring codewords illegally diffused by end users;

Step 3, according to the codeword, determine that at least one of the current co-conspirators is from the group where the codeword is located;

以获得剩余嫌疑共谋组的组合C\C₁，其中U为终端用户，T为任意可能的共谋者的数量，G为将所述U个终端用户分成的组数，C\C₁为在组合C中排除组合C1； Step 4, exclude the combination of the suspected colluding group from the combination C(U, T) of the current colluding group

To obtain the combination C\C ₁ of the remaining suspected colluding groups, where U is the terminal user, T is the number of any possible co-conspirator, G is the number of groups that divide the U terminal users into, and C\C ₁ is Exclude combination C1 from combination C;

Description of drawings

Step 5, judging whether there is at least one co-conspirator in the combination of the remaining suspected colluding groups;

Step 6, if the judgment result is yes, then determine that the co-conspirator is a pirate;

Step 7, if the judgment result is no, group the terminal users according to the combination of the remaining suspected collusion groups, perform steps 2 to 5, and repeat the above steps until at least one collusion exists in the combination of the remaining suspected collusion groups By. the

In order to achieve the above object, the present invention also provides a pirate tracking system, the system includes a plurality of terminals, and the terminal can be specifically understood as a set-top box or a user combined with a certain IC card; wherein, the system also includes:

A monitoring unit, which is used to monitor codewords illegally diffused by end users;

A tracking unit, connected to the monitoring unit, is used to determine the pirates among the end users by using the combined elimination method according to the monitored codewords;

A grouping unit, the grouping unit is connected to the tracking unit, and is used to group the current end users according to the tracking results of the tracking unit, and transmit the grouping results to the distribution unit;

An allocation unit, which is connected to the grouping unit and the terminal, and is used to allocate a different codeword for each group according to the grouping result, and send the codeword to the terminal

It also includes a judging unit, which is respectively connected to the grouping unit and the monitoring unit, and the judging unit performs the following processing:

Exclude the combination of the suspected collusion group from the combination C(U, T) of the current collusion group To obtain the combination C\C ₁ of the remaining suspected colluding groups, where U is the terminal user, T is the number of any possible co-conspirator, G is the number of groups that divide the U terminal users into, and C\C ₁ is Exclude combination C1 from combination C; judge whether there is at least one co-conspirator in the combination of the remaining suspected colluding groups; if the judgment result is yes, then determine that the co-conspirator is a pirate; Using the grouping unit to group the end users according to the combination of the remaining suspected colluding groups, the judging unit repeats the above processing until at least one co-conspirator exists in the combination of the remaining suspected colluding groups.

The beneficial effect of the present invention is that the combination exclusion method is used to track the pirates, which solves the bottleneck problem of the existing pirates tracking, that is, the problem restricted by the number of user groups and the increase in the number of user groups, the cost, technical realization and other conditions. , and the tracking efficiency is high; and the interests of operators are maintained. the

The drawings described here are used to provide further understanding of the present invention, constitute a part of the application, and do not limit the present invention. In the attached picture:

Fig. 1 is a schematic structural diagram of a pirate tracking system in the related art;

Fig. 2 is that the present invention implements the flow chart of pirate's tracking method;

Fig. 3 is a schematic structural diagram of a system for tracking pirates according to an embodiment of the present invention. the

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the embodiments and accompanying drawings. Here, the exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but not to limit the present invention. the

The present invention provides a pirate tracking system, as shown in Figure 3, the system includes a plurality of terminals; in addition, the system also includes:

The monitoring unit 301 is used to monitor the code word illegally diffused by the end user; the tracking unit 302 is connected to the monitoring unit 301 and is used to determine the pirate among the end users by using the combined elimination method according to the monitored code word. the

From the above, it can be seen that the existing bottleneck problem of pirate tracking is solved by adopting the combined elimination method to track pirates, the tracking efficiency is high, and the interests of operators are maintained. the

Wherein, the terminal may be a set-top box combined with an IC card. the

In addition, in this embodiment, the system also includes a grouping unit 303 and a distribution unit 305; wherein, the grouping unit 303 is connected to the tracking unit 302, and is used to group the current terminal users according to the tracking results of the tracking unit 302, and assign The grouping result is sent to the allocation unit 305;

The allocation unit 305 is configured to allocate a different codeword to each group according to the grouping result of the grouping unit 303, and send the codeword to the terminal. the

As shown in FIG. 3 , the system further includes an output unit 304 connected to the tracking unit 302 for outputting tracked pirates. the

The present invention also provides a method for tracking pirates, which includes: determining the pirates among the terminal users by using the combined exclusion method according to the monitored illegally diffused codewords. the

By adopting the combined exclusion method to track pirates, it solves the bottleneck problem of existing pirates tracking, that is, the problem that is restricted by the number of user groups and the increase in the number of user groups, the cost, technical implementation and other conditions, and the tracking efficiency is high. Protect the interests of operators. the

In the present invention, after determining the pirate, it further includes: outputting the pirate. In this way, the pirate terminal can be disconnected according to the output pirate information. the

In the present invention, according to the code word, the pirates in the terminal users are determined by the combination exclusion method, the following methods can be adopted: Step 1, the current terminal users are grouped, and different code words are assigned to each group; Step 2 , to monitor the code word illegally diffused by the end user; step 3, according to the code word, determine that at least one of the current co-conspirators is from the group where the code word is located; step 4, eliminate the suspected collusion group according to the combination of the current co-conspiracy group to obtain the combination of the remaining suspected colluding groups; step 5, judge whether there is at least one co-conspirator in the combination of the remaining suspected colluding groups; step 6, if the judgment result is yes, determine the co-conspirator for pirates. the

In addition, the method also includes: judging whether all co-conspirators are found; if the judging result is yes, it means that all pirates have been traced, and the tracing process ends. If the judgment result is no, repeat steps 1 to 6 until all accomplices are found. the

The present invention will be described in detail below in conjunction with accompanying drawings 2 and 3 . the

First, let U be the total number of terminal users in the system, T be the number of co-conspirators, and G be the maximum number of user groups that can be used. In this way, at the beginning of tracking, any selection of T from U end users may be a collusion group, denoted as C, and its combination is |C|=C(U, T). the

Steps 201, 202, 203, tracking starts, the grouping unit 303 evenly divides users into G groups, and the allocation unit 305 allocates different codewords for each group, for example, the allocated codewords are {1, 2, ..., G };

Step 204, the monitoring unit 301 monitors the illegally diffused codeword, if the codeword illegally diffused by the collusion group is 1; wherein, the terminal user can diffuse through telephone, text message, network, etc.;

个嫌疑共谋组被排除，即第一步被排除的共谋组合的集合记为C₁，这样可获得剩余嫌疑共谋组合的集合为C\C₁。用|C₁|表示C₁的大小，则 

Step 205, the judging unit 302 judges according to the monitored information, and learns that at least one of the co-conspirators is from group 1, and it is impossible for all of them to come from {2, 3, ..., G} group; according to the current co-conspirator's The combination excludes the combination of the suspected co-conspirator to obtain the combination of the remaining co-conspirator. In this way, because the current combination of the co-conspirator is C, and there is

The suspected collusion groups are excluded, that is, the set of the excluded collusion combinations in the first step is recorded as C ₁ , so that the set of the remaining suspected collusion combinations can be obtained as C\C ₁ . Denote the size of C ₁ by |C ₁ |, then

Step 206, judging whether at least one co-conspirator can be determined according to the combination of the remaining suspected colluding groups, in this embodiment, the following method can be adopted: that is, judging whether there is at least one co-conspirator in the combination of the remaining colluding groups ;

Step 207, if the judgment result is yes, then determine that the co-conspirator is a pirate, at this moment the output unit 304 outputs the pirate, and disconnects the pirate terminal from the system;

In step 206, if the judgment result is negative, indicating that the pirate cannot be determined yet, then return to step 201, and discharge more remaining suspected user groups until the pirate can be determined according to the combination of the remaining suspected colluding groups. Among them, the following methods can be used:

而实际根据这一步可排除的嫌疑组合数可能小于|B₂|，因为此次的嫌疑共谋组B₂中还可能包括与C₁共同的组合，即 

因此，记在此步中能有效排除的嫌疑共谋组的组合为C₂，则C₂＝B₂-C₁∩B₂； The grouping unit 103 groups the users according to the remaining suspected collusion combinations, the allocation unit 305 redistributes the codewords to the terminals, and the monitoring unit 301 monitors the illegally diffused codewords; Exclude the suspected colluding group. Note that the set of suspected collusion combinations excluded based on the feedback information of this step is B ₂ , then there is

In fact, the number of suspected combinations that can be excluded according to this step may be less than |B ₂ |, because the suspected collusion group B ₂ may also include the common combination with C ₁ , namely

Therefore, record the combination of suspected colluding groups that can be effectively eliminated in this step as C ₂ , then C ₂ =B ₂ -C ₁ ∩B ₂ ;

By analogy, record the set of suspected combinations excluded only based on the feedback information in step i as B _i , and record the set of suspected combinations that can be effectively eliminated in step i as C _i , then Bi and _{C i} The relationship is as follows:

C ₁ =B ₁

C ₂ ＝B ₂ -C ₁ ∩B ₂

C ₃ ＝B ₃ -(C ₁ ∪C ₂ )∩B ₃

${\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\underset{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{<span\; class="notranslate">\; \&cup;</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&cap;</span>{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}$

如果能够根据剩余嫌疑组合推断出一个盗版者，则输出该盗版者，断开该盗版者终端与系统的连接； At step i, the combination of the remaining suspected colluding groups is

If a pirate can be deduced according to the remaining suspect combinations, then output the pirate and disconnect the pirate terminal from the system;

Step 208, judging whether to find out all pirates, that is, judging whether the number of co-conspirators in step 206 is T, if it is T, it means that all pirates are found through the above steps, and the tracking process ends. the

If the number K of co-conspirators determined in step 206 is less than T, it means that not all pirates have been found, and then return to step 201 to track pirates. In this case, at the beginning of each trace, the current number of end users is U-K, the number of co-conspirators is T-K, and the maximum number of user groups that can be used is still G. In this way, at the beginning of tracing, any combination of T-K end users selected from U-K end users may be the combination of the current collusion group, and so on until U-K=0. the

排除的组合数占总组合数的比例称为排除率可为： It can be seen from the above that when using the above combination exclusion method, the number of combinations |C _i | to be excluded each time is close to

The ratio of the number of excluded combinations to the total number of combinations is called the exclusion rate, which can be:

$\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; |</span>}{<span\; class="notranslate">\; |</span>\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; |</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; G</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; G</span>}}\mathrm{<span\; class="notranslate">\; u</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; u</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \&ap;</span>{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; G</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; G</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; no</span>}}$

Among them, r can be regarded as an estimate of the convergence speed of the combined exclusion method. It can be seen that the convergence speed of tracking increases with the increase of G and decreases with the increase of T. the

Therefore, as can be seen from the foregoing embodiments, this method solves the bottleneck problem of existing pirates tracking, that is, the problem of being restricted by the number of user groups and the increase in the number of user groups, the cost, technical implementation and other conditions, and the tracking efficiency is high. Protect the interests of operators. the

The following is an illustration with a practical example. For example, for a problem where the total number of users is U=100 and there are T=6 users colluding, the maximum number of user groups that can be used is G=5, with 20 people in each group. the

In this way, at the beginning of tracking, any 6 of the 100 end users may be selected as a collusion group, denoted as C, and its combination is |C|=C(U, T), that is

1) At the beginning of tracking, the grouping unit 303 divides the users evenly into 5 groups, and the allocation unit 305 allocates different codewords for each group respectively, such as the allocated codewords are {1, 2, 3, 4, 5};

2) Monitoring unit 301 monitors the code word of illegal diffusion, if the code word of collusion group illegal diffusion is 1;

排 除嫌疑共谋者的组合 

以获取剩余共谋者的组合为 

个； 3) Judgment unit 302 judges according to the monitored information, and learns that at least one of the co-conspirators comes from group 1, and it is impossible for all of them to come from {2, 3, 4, 5} groups; according to the current combination of co-conspirators

Combinations that exclude suspected co-conspirators

To obtain the combination of the remaining colluders as

indivual;

4) Judging whether at least one co-conspirator can be determined according to the combination of the remaining suspected colluding groups, in this embodiment, the following method can be adopted: that is, judging whether there is at least one co-conspirator in the combination of the remaining suspected colluding groups; If the judgment result is yes, then it is determined that the co-conspirator is a pirate, and at this moment the output unit 304 outputs the pirate, and disconnects the pirate terminal from the system;

5) If the judgment result is that there is no co-conspirator in the combination of the remaining colluding groups, it means that the pirate cannot be determined yet, then repeat the above steps 1)-4), and discharge more remaining suspected user groups until it can be determined according to The combination of the remaining suspected colluding groups identifies the pirate. Among them, the following methods can be used:

而实际根据这一步可排除的嫌疑组合数可能小于 

因为此次的嫌疑共谋组B₂中还可能包括与C₁共同的组合，即 

因此，记在此步中能有效排除的嫌疑共谋组的组合为C₂，则C₂＝B₂-C₁∩B₂； The grouping unit 103 groups the users according to the remaining suspected collusion combinations, the allocation unit 305 redistributes the codewords to the terminals, and the monitoring unit 301 monitors the illegally diffused codewords; Exclude the suspected colluding group. Note that the set of suspected collusion combinations excluded only based on the feedback information of this step is B ₂ , then we have

In fact, the number of suspected combinations that can be excluded according to this step may be less than

Because the suspected conspiracy group B ₂ may also include a combination with C ₁ , namely

Therefore, record the combination of suspected colluding groups that can be effectively eliminated in this step as C ₂ , then C ₂ =B ₂ -C ₁ ∩B ₂ ;

By analogy, record the set of suspected combinations excluded only based on the feedback information in the i-th step as B _i , record the set of suspected combinations that are effectively excluded in the i-th step as C _i , then the relationship between Bi and _{C i} The relationship is as follows:

C ₁ =B ₁

C ₂ ＝B ₂ -C ₁ ∩B ₂

C ₃ ＝B ₃ -(C ₁ ∪C ₂ )∩B ₃

${\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\underset{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{<span\; class="notranslate">\; \&cup;</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&cap;</span>{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}$

如果能够根据剩余嫌疑组合推断出一个盗版者，则输出该盗版者，断开该盗版者终端与系统的连接； At step i, the combination of the remaining suspected colluding groups is

If a pirate can be deduced according to the remaining suspect combinations, then output the pirate and disconnect the pirate terminal from the system;

6) Judging whether to find out all 6 pirates, that is, judging whether the number of co-conspirators in 5) is 6, if it is 6, it means that all pirates are found through the above steps, and the tracking process ends. the

If the number K of co-conspirators determined in step 5) is less than 6, it means that not all pirates have been found, and steps 1-5) are repeated to track pirates. In this case, at the beginning of each trace, the current number of end users is 100-K, the number of co-conspirators is 6-K, and the maximum number of user groups that can be used is still G. In this way, at the beginning of the trace, any combination of 6-K end users selected from 100-K end users may be the combination of the current collusion group, and so on until 6-K=0. the

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the scope of the present invention. Protection scope, within the spirit and principles of the present invention, any modification, equivalent replacement, improvement, etc., shall be included in the protection scope of the present invention. the

Claims (6)

1. A method for tracking a pirate, the method comprising: determining pirates in the terminal users by adopting a combined elimination method according to the monitored illegally spread code words,

wherein the determining of the pirate in the end user by adopting a combined elimination method according to the code words comprises:

step 1, grouping the current terminal users and distributing different code words to each group;

step 2, monitoring illegal diffused code words of the terminal user;

step 3, determining at least one of the current colluders from the group where the code word is located according to the code word;

step 4, eliminating the combination of the suspected collusion group in the combination C (U, T) of the current collusion group

To obtain the combination C \ C of the remaining suspected collusion groups₁Wherein U is a terminal user, T is the number of any possible colluders, G is the number of groups into which the U terminal users are divided, C \ C₁To exclude combination C from combination C₁；

Step 5, judging whether at least one colluder exists in the combination of the remaining suspected collusion groups;

step 6, if the judgment result is yes, the collusion person is determined to be a pirate;

and 7, if the judgment result is negative, grouping the terminal users according to the combination of the remaining suspected collusion groups, performing the steps 2 to 5, and repeating the steps until at least one colluder exists in the combination of the remaining suspected collusion groups.

2. The method of claim 1, further comprising: and outputting the pirate.

3. The method of claim 1, further comprising:

judging whether all colluders are found;

if the judgment result is yes, the tracking is finished.

4. The method of claim 3, wherein if the determination of whether all colluders are found is negative, then repeating steps 1 through 7 until all colluders are found.

5. A pirate tracing system comprises a plurality of terminals; characterized in that, the system also includes:

the monitoring unit is used for monitoring the code words illegally spread by the terminal user;

the tracking unit is connected with the monitoring unit and used for determining a pirate in the terminal user by adopting a combination elimination method according to the monitored code word;

the grouping unit is connected with the tracking unit and used for grouping the current terminal user according to the tracking result of the tracking unit and transmitting the grouping result to the distribution unit;

the distribution unit is connected with the grouping unit and the terminal and used for distributing different code words to each group according to the grouping result and sending the code words to the terminal;

the device also comprises a judging unit which is respectively connected with the grouping unit and the monitoring unit, and the judging unit carries out the following processing:

exclusion of combinations of suspect collusion groups in combinations C (U, T) of current collusion groups

To obtain the combination C \ C of the remaining suspected collusion groups₁Wherein U is a terminal user, T is the number of any possible colluders, G is the number of groups into which the U terminal users are divided, C \ C₁To exclude combination C from combination C₁(ii) a Judging whether at least one colluder exists in the combination of the remaining suspected collusion groups; if the judgment result is yes, the colluder is determined to be a pirate, if the judgment result is no, the grouping unit is used for grouping the terminal user according to the combination of the remaining suspected collusion groups, and the judgment unit repeats the processing until at least one colluder commonly exists in the combination of the remaining suspected collusion groups.

6. The system of claim 5, further comprising an output unit coupled to the tracking unit for outputting the pirate.

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