Data control method, for embedding data control information,...

Details Data control method, for embedding data control information,... Data control method, for embedding data control information,...

1998-07-06

2002-08-13

Trammell, James P. (Department: 2164)

Data processing: financial, business practice, management, or co

Business processing using cryptography

Usage protection of distributed data files

C705S051000, C705S052000, C705S059000, C380S001000, C380S001000, C380S001000, C380S029000, C380S029000, C360S025000, C360S060000

Reexamination Certificate

active

06434538

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for embedding data control information for controlling the permission or prohibition to copy recorded data in order to prevent data whose copyright should be protected (e.g., an audio software, a graphic software, or the like) from being copied or processed (i.e., manipulated), and a device for realizing the method; a method for detecting such data control information, and a device for realizing the method; and a data control method in which the method for embedding data control information and the method for detecting data control information are combined.
2. Description of the Related Art
As a method for embedding copy control information in an image, or as a method for detecting copy control information, a method referred to as Patchwork is known. This method is described in “Data hiding techniques for supporting water mark (I)”, Nikkei Electronics, No. 683, pp. 149-162, published in Feb. 24, 1997 (this is a translation of “Techniques for data hiding” by W. Bender, D. Gruhl, N. Morimoto, and A. Lu, IBM Systems Journal, Vol 35, NOS 3 & 4, 1996). Hereinafter, a conventional method for embedding copy control information and a conventional method for detecting such a copy control information will be described.
As the conventional method for embedding copy control information, a process for embedding a copy permission/prohibition bit (one bit) in an image will be described hereinafter. When copying is permitted, the copy permission/prohibition bit is set to be 1. When copying is prohibited, the copy permission/prohibition bit is set to be 0. Two points (i.e., Ai and Bi) are selected from the image by means of pseudo random numbers. Next, when a bit to be embedded is 1, the brightness level of Ai, i.e., Yai, is raised by an amount d, and the brightness level of Bi, i.e., Ybi, is lowered by the amount d. Conversely, when a bit to be embedded is 0, the brightness level of Ai is lowered by the amount d, and the brightness level of Bi is raised by the amount d. The value of d is an integer from 1 to 5. Such processing is repeated n times (n is generally about 10,000).
Next, the conventional method for detecting copy control information will be described. First, brightness levels (i.e. pixel information) at the same two points as those selected at the time of embedding information (i.e., (Yai+d, Ybi−d) or (Yai−d, Ybi+d)) are extracted from the image by pseudo random numbers. Next, the difference between these two points is calculated. These processing steps are repeated n times, and a mean value of the thus-obtained differences is calculated. If the mean value is equal to or greater than d, the embedded bit is considered to be 1, and if the mean value is equal to or less than −d, the embedded bit is considered to be 0. If the mean value is between −d and d, it is considered that no information is embedded.
Herein, the expected value of (Yai−Ybi) is estimated to be 0. The expected value of (Yai+d)−(Ybi−d) is 2d, and the expected value of (Yai−d)−(Ybi+d) is −2d. Accordingly, determination is performed assuming that the threshold values of displacement from the mean value of 0 are d and −d. In order to perform more accurate determination, copy control information can be detected by finding the statistical distribution of such differences, and measuring the displacement of its variance from the estimated value.
As described above, according to the conventional method for embedding copy control information and the conventional method for detecting copy control information, it is possible to embed and detect a one-bit copy permission/prohibition flag. According to another method, a constant level d is not added or subtracted in the selected pixels. Rather, information is embedded as follows. The level of embedding is changed for each of the pixels in accordance with the characteristics of its image, and such a level is respectively added to, or subtracted from, the brightness of each of the pixels so that the mean of such calculations becomes level d. As a result, it is possible to suppress the deterioration of the image after embedding the information and to make it more difficult to conduct tampering.
Therefore, the method for embedding copy control information and the method for detecting the copy control information are required not only to indicate the permission or prohibition to copy but also to control the number of allowed copies (e.g., to control the number of copies so as to limit the number of copies made to N). In order to control the number of copies, it is necessary to rewrite copy control information upon copying. For example, in the case of a software whose copying is permitted only once, the copy control information indicating that copying is permitted once is embedded in the software. Upon copying the software, the copy control information must be replaced by new copy control information indicating copying is prohibited.
In order to realize such rewriting of copy control information by the conventional method for embedding copy control information and the conventional method for detecting the copy control information, both of these methods must be executed when a user makes a copy. Since the conventional method for embedding copy control information is hard to process as compared to the method for detecting the copy control information, its realization by a user leads to an increase in cost. In addition, since the method for embedding copy control information is disclosed to the user, there exists a possibility that tempering can be carried out rather easily.
SUMMARY OF THE INVENTION
According to one aspect of this invention, a data control method includes the steps of: A) at least one of the following steps: A-1) embedding prohibition information in data, wherein copying of the data is to be prohibited; and A-2) embedding the prohibition information and N pieces of permission information in the data (N is a natural number), wherein the copying of the data is to be permitted N times; and B) detecting the prohibition and/or permission information prior to the copying of the data. In the case where the permission information is detected from the data prior to the copying of the data, at least one of the N pieces of permission information in the data is invalidated, and then the copying of the data is permitted. In the case where the permission information is not detected from the data, and the prohibition information is detected from the data prior to the copying of the data, the copying of the data is prohibited.
In one embodiment of the present invention, the permission information is a digital signature f(M); and the digital signature f(M) is derived based on a digital code M which is extracted from the data.
According to another aspect of this invention, a method for embedding data control information includes one of the following steps of: embedding prohibition information in data, wherein copying of the data is to be prohibited; and embedding the prohibition information and N pieces of permission information in the data in the data (N is a natural number), wherein the copying of the data is to be permitted N times.
In one embodiment of the present invention, the permission information is a digital signature f(M) for a digital code M which is uniquely derived from the date.
According to still another aspect of this invention, a method for detecting data control information includes the step of detecting predetermined permission and/or prohibition information prior to copying of data. In the case where the predetermined permission information is detected from the data prior to the copying of the data, the predetermined permission information is invalidated so as to permit the copying of the data. In the case where the predetermined permission information is not detected from the data, and the predetermined prohibition information is detected from the data prior to the copying of the data, t

Affiliated with

Also associated with

Rating

Data control method, for embedding data control information,... does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Data control method, for embedding data control information,..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Data control method, for embedding data control information,... will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2880969