CN1127240C - Security Method of Multimedia Data - Google Patents

Abstract

A method for securing multimedia data includes an encryption/decryption table, which is composed of an index value and encryption operation. Any index value corresponds to an encryption operation, key data in the multimedia data is encrypted/decrypted by using an encryption/decryption table, and the reliability of encryption is improved through one or more encryption operations in the table. During encryption/decryption, the encryption/decryption table, the key data position of the multimedia data and the index value of the encryption/decryption must be obtained at the same time to perform encryption/decryption, thereby improving the reliability and security of data security.

Description

Security Method of Multimedia Data

technical field

The invention relates to a method for securing multimedia data.

Background technique

In today's information communication field, the use of multimedia data as a means of communication transmission will promote the development of the information communication industry. Considering special reasons such as copyright, privacy or security of general multimedia data, various data are often encrypted. The specific method is: (1) encrypt all data; (2) use very complex algorithms to Prevent illegal decryption, and because the data volume is usually very large, and the sound needs to be played immediately without delay, therefore, if a very complex algorithm is used for encryption, the effect of data and sound playback will be affected. If all data is encrypted , not only will occupy a considerable storage space for decrypted information, but also be easily cracked by illegal persons. Therefore, the existing encryption methods cannot effectively achieve the purpose of keeping data confidential, resulting in insecurity. Thereby causing troubles in use.

Contents of the invention

For above-mentioned existing various shortcoming, an object of the present invention is to provide a kind of security method of multimedia data, it is a kind of fast, effective and easy encryption method for a multimedia data, according to the intrinsic characteristic of multimedia data only The key data but not all data are encrypted to reduce the amount of calculation, so that a large amount of multimedia data can be quickly encrypted/decrypted; and one or more encryption methods in the encryption/decryption table are used for comprehensive encryption, thereby increasing security Security of multimedia data encryption.

Another object of the present invention is to provide a method for securing multimedia data, in which the encryption operation can be designed by itself, the encryption operation corresponding to the index value in the encryption/decryption table randomly repeats, and the encryption operation corresponding to each other index value The operations can be the same or different, and the more encryption operations, the higher the security.

For realizing the purpose of the present invention, a kind of security method of multimedia data is provided, is used for encrypting and decrypting multimedia data, and the method comprises:

An encryption/decryption table, which is composed of an index value (index) and an encryption operation, and any index value in the table corresponds to an encryption operation, and the index value cannot appear repeatedly;

In the process of encrypting multimedia data, the two parties in communication pre-agreed on the key data that needs to be encrypted in a kind of multimedia data to be transmitted, and the multimedia data is composed of multiple frames; wherein the encryption process includes the following steps:

(1) First, find out the key data positions to be encrypted in any frame except the first frame in the data;

(2) Find out the location corresponding to the key data that can be used to store the index value;

(3) Select whether to encrypt the key data, if not encrypt, then go to step (6), if encrypt then continue;

(4) Randomly select a piece of data from the encryption/decryption table as an encrypted index value, and encrypt the key data according to the encryption operation corresponding to the index value in the encryption/decryption table;

(5) storing the selected index value in multiple frames of the data;

(6) judge whether there is unencrypted key data, if so then get back to step (2), otherwise all encryption ends;

In the process of decrypting the encrypted multimedia data, use the index value to compare and find out the encryption operation in the table for decryption; wherein the decryption process includes the following steps:

(1) First, find out the key data position to be decrypted in any frame in the data;

(2) Find out the storage location of the index value corresponding to the key data;

(3) Find out the original original data at the position of the index value after being encrypted and covered, that is, the data in the first frame;

(4) compare the encrypted index value with the original data, if they are the same, it means that the key data is not encrypted, then go to step (6), if they are not the same, continue;

(5) According to the data stored in the plurality of frames according to the encryption index value, the encryption operation used to find out the key data is compared with the encryption/decryption table, and the original key data before encryption can be obtained, and decrypted accordingly , restore the original data covered by the index value;

(6) Judging whether there is any unencrypted key data, if so, then return to step (1), if not, then all decryption ends.

Since the encryption/decryption index value of the above method is included in the data, it does not need to occupy additional storage space to store the encryption/decryption information, therefore, it will not affect the multimedia data and sound playback effect, and the encryption/decryption must be obtained at the same time. The encryption/decryption table, the key data position of multimedia data and the index value of encryption/decryption can be encrypted/decrypted, thereby improving the reliability of encryption/decryption and increasing the security.

Description of drawings

In order to further understand and understand the purpose, features and functions of the present invention, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the attached picture:

Fig. 1 is basic encryption/decryption table of the present invention:

Fig. 2 is the data structure schematic diagram of the present invention;

Fig. 3 is the MP3 encryption/decryption table of the embodiment of the present invention;

Fig. 4 is the encryption operation flowchart of the present invention;

Fig. 5 is a flowchart of the decryption operation of the present invention.

Detailed ways

As shown in Figure 1, Figure 2, Figure 3, Figure 4 and Figure 5. The encryption method for multimedia data of the present invention has an encryption/decryption table 10, as shown in FIG. 1 . The encryption/decryption table 10 is composed of an index value and an encryption operation. The size of each index value cannot exceed the maximum value that can be represented by 4 bits, that is, 15 (decimal), and each index value corresponds to an encryption operation. At the same time, index values cannot appear repeatedly. And for the sake of security, the encryption/decryption table 10 cannot be included in the encrypted (ie key data) data. At the same time, in the encryption process, the same encryption/decryption table 10 must be used at the same time, and the data can be encrypted using the encryption/decryption table 10; Encryption operation for decryption.

In the multimedia data encryption process of the present invention, the communication parties must first agree on a key data that must be encrypted in the transmitted data. The data structure adopted therein is shown in Fig. 2, it has multiple frames, any frame has a main data beginning part ④ (main data begin, 9 bits). This part of data ④ can point out the storage location of the actual data in the current frame. If this part of data ④ is changed, it is enough to affect the whole data. The starting part ④ of the main data in any frame is the key data, and is the object of encryption. Moreover, select an encryption operation and its corresponding index value storage location in the encryption/decryption table 10.

As shown in Figure 2, before the main data start part ④ in any frame, respectively be provided with: ①: ID (identification bit, 1 bit); ②: Lay (data layer number, 2 bits); ③: Protect (protect bit, 1 bit), a total of four bits of data. In a basic data unit to be encrypted (such as a song, a paragraph), the four bits of data in each frame are the same. Therefore, it is agreed to use these data ①, ②, ③ to store the encrypted index value (of course, the size of the index value cannot exceed the maximum value that can be represented by 4 bits, that is, 15). In addition, in the international standard ISO/IEC 11172-3, there are standard algorithms for how to find the positions of these data ①, ②, ③, and ④. Since it is not the invention point of the present invention, it will not be described here.

According to the international standard ISO/IEC 11172-3, the data produced by Layer 3 is a kind of multimedia data, hereinafter referred to as MP3 data. Assume that multimedia data of a song in MP3 format is now produced. After making it, you will find that its data form is composed of many frames. The 12th bit in each frame is ID (counting from 0), the 13th and 14th bits are Lay, and the 15th bit is Protecy. These 4 bits of data are the same in all frames of the song. Therefore, the 4-bit data in the first frame is reserved, and the four-bit data of ID, Lay, and Protect in each subsequent frame can be obtained from the first frame. Therefore, the position of the 4-bit data in other frames except the first frame can be used to store the index value (index) used for encryption/decryption. When decrypting, take out the index value from these 4 bits and perform decryption. And the original value of these 4 bits is obtained from the first frame.

Also, there are no rules about where the actual sound data is stored in each frame. According to the ISO/IEC11172-3 international standard, a 9-bit data can be found in each frame according to the standard algorithm, called main data begin. The purpose of this data is to indicate where the actual sound data in this frame starts. The error of this data will make it impossible to restore the sound, so only encrypting this data item in each frame is enough to achieve the effect of encrypting the entire song.

Prior to this, all data for the entire song was usually encrypted with one encryption method. However, because all the data needs to be decrypted during playback, once the decryption algorithm is too complicated, the playback speed cannot keep up with the actual sound speed, causing the sound to pause; and if a simple encryption/decryption algorithm is used, it is very difficult. It is easy to be cracked illegally. Therefore, the present invention overcomes the above contradictions and achieves satisfactory results in actual use.

The encryption method of an embodiment of the present invention is described below with reference to Fig. 4:

(1) First, find out the key data to be encrypted in any frame except the first frame of this MP3 data, i.e. the position of the main data starting part ④;

(2) Find out the location that can be used to store the index value corresponding to the key data;

(3) choose whether to encrypt this key data, if not encrypt, then go to step (6), if encrypt then continue;

(4) Randomly select a data not greater than 15 and not equal to the original 4 bits from the MP3 encryption/decryption table 10' as shown in Figure 3, as an encrypted index value, and according to the MP3 encryption/decryption table 10' The encryption operation corresponding to the index value encrypts the key data; for example, if the index value is 7, the corresponding encryption operation is to add the index value to the key data;

(5) Store the index value 7 in the four bits of ①: ID, ②: Lay, ③: Protect in the frame of the MP3 data;

(6) Judging whether there is any unencrypted key data, if so, return to step (2), otherwise all encryption ends.

On the contrary, with reference to shown in Figure 5, in the decryption process, the decryption method of the embodiment of the present invention is as follows:

(1) First, find out the key data to be decrypted in any frame of this MP3 data, i.e. the position of the main data start part ④;

(2) Find out the position of storing the index value corresponding to the key data, that is, the four bits ①: ID, ②: Lay, ③: Protect in the frame;

(3) Find out the original data of the four bits of ①: ID, ②: Lay, ③: Protect on the position of the index value after being encrypted and covered. In this embodiment, it is ① in the first frame : ID, ②: Lay, ③: four bits of Protect;

(4) compare the encrypted index value with the original data, if they are the same, it means that the key data is not encrypted, then go to step (6), if they are not the same, continue;

(5) according to the stored four bit data of this encryption index value, contrast MP3 encryption/decryption table 10 ', find out the encryption operation that this key data adopts; In the present embodiment, its index value is 7, and its corresponding The encryption operation is to add the index value to the key data; therefore, subtract the index value from the encrypted key data to obtain the original key data before encryption, and decrypt it accordingly; at the same time, restore the key data covered by the index value The original data is the four bits of information in the frame: ①: ID, ②: Lay, ③: Protect;

(6) Judging whether there is any undecrypted key data, if there is, then return to step (1), if not, then all the decryption process ends.

In the present invention, the encryption operation used can be designed by itself, as shown in FIG. 1 . The encryption operations corresponding to the index values 0, 1, and 2 in the encryption/decryption table 10 may repeat randomly, for example, the encryption operations corresponding to the index values 0 and 3 may be the same or different. And the more encryption operations, the higher the security. In addition, even if an illegal cracker obtains the encryption/decryption table 10, if he does not know which data is the key data in any multimedia data format and where the index value is stored, he will have no way of doing it.

In addition, according to the international standard ISO/IEC 13818-3, the data made by Layer 3, the main data start part ④ (11 bits) in the frame is also suitable for the encryption method of the present invention.

Although a preferred embodiment of the present invention has been described in detail above, various equivalent modifications and changes made by those skilled in the art according to the content disclosed in the present invention should be included in the claims defined in the present invention. In the range.

Claims (4)

1. A method for securing multimedia data, used for encrypting and decrypting multimedia data, the method comprising: An encryption/decryption table, which is composed of index values and encryption operations, and any index value in the table corresponds to an encryption operation, and the index value cannot appear repeatedly; In the process of encrypting multimedia data, the two parties in communication pre-agreed on the key data that needs to be encrypted in a kind of multimedia data to be transmitted, and the multimedia data is composed of multiple frames; wherein the encryption process includes the following steps: (1) First, find out the key data positions to be encrypted in any frame except the first frame in the data; (2) Find out the location corresponding to the key data that can be used to store the index value; (3) Select whether to encrypt the key data, if not encrypt, then go to step (6), if encrypt then continue; (4) Randomly select a piece of data from the encryption/decryption table as an encrypted index value, and encrypt the key data according to the encryption operation corresponding to the index value in the encryption/decryption table; (5) storing the selected index value in multiple frames of the data; (6) judge whether there is unencrypted key data, if so then get back to step (2), otherwise all encryption ends; In the process of decrypting the encrypted multimedia data, use the index value to compare and find out the encryption operation in the table for decryption; wherein the decryption process includes the following steps: (1) First, find out the key data position to be decrypted in any frame in the data; (2) Find out the storage location of the index value corresponding to the key data; (3) Find out the original original data at the position of the index value after being encrypted and covered, that is, the data in the first frame; (4) compare the encrypted index value with the original data, if they are the same, it means that the key data is not encrypted, then go to step (6), if they are not the same, continue; (5) According to the data stored in the plurality of frames according to the encryption index value, the encryption operation used to find out the key data is compared with the encryption/decryption table, and the original key data before encryption can be obtained, and decrypted accordingly , restore the original data covered by the index value; (6) Judging whether there is any unencrypted key data, if so, then return to step (1), if not, then all decryption ends. 2. The multimedia data security method as claimed in claim 1, wherein the size of any index value in the encryption/decryption table cannot exceed the maximum value that 4 bits can represent, i.e. 15, and the encryption/decryption table cannot Included in the encrypted key data, at the same time, during the encryption process, the same encryption/decryption table is used to encrypt the audio data. 3. The multimedia data security method as claimed in claim 2, wherein any frame formed by the audio data has a main data start portion, as the key data of the encrypted object, before the main data start portion , respectively setting a plurality of bit data in a basic audio data unit to be encrypted, and setting the plurality of bits to store the encrypted index value. 4. The multimedia data security method as claimed in claim 3, wherein a plurality of bit data before the main data start portion are respectively an identifier of a bit, a data layer number of two bits, a protection bit of a bit, A total of four bits of data.

Images