Technical field of the invention

The present invention generally relates to a method for media content encryption and decryption, more particularly the present invention relates to a method for media content encryption and decryption for restricting access to the media content. Background of invention

The issue of copyright infringement of media content has been a nuisance to the creative industry. More often than not the media content is published on the internet for easy access to users. Such phenomenon will affect the authors adversely if their work is not protected appropriately, where their media works such as graphics, video and music will be copied or downloaded, modified or shared illegally by unauthorized users. However, for various reasons such as promotional or marketing purposes, the media content should not be restricted from viewing by the unauthorized users. Rather, a limitation should be imposed to the media data.

The prior art US 2005/0069129 (Al) discloses a method of protecting copyright of a digital video work by using a digital password technology and a digital watermark technology to prevent the unauthorized use of the content. The users would have to request or purchase the correct password and a specific video player. However, the prior art did not mention setting of a limitation parameter to limit the access of unauthorized user. An authorized user would be able to view the content of the digital video work as long as a specific player is used with the correct password .

The prior art US 2007/0237328 (Al) discloses a method for encrypting a video data by interchanging video data blocks from two subsets of video data blocks with a permutation list to create a temporary cipher text, in which the permutation list being generated by means of the first key stream derived from a stream cipher source. The prior art also discloses the use of a further second key stream when encrypting the temporary cipher text, in which the second key stream is also generated with the stream cipher source. However, the prior art did not mention about setting an allowable range of parameter for restricting the use of the media content.

The prior art US 7,751,560 (B2) discloses a method for producing multiple partially encrypted television signal. An encrypted sample of the television signal is generated under a first encryption method. Another encrypted sample of the television signal is generated under a second encryption method. The encrypted samples are then combined using a multiplexing device to produce the partially multiple encrypted television signals. The prior art utilizes multiple encryption method to further enhance the security. There is no mention of limitation parameters and also partial encryption of the media content in the prior art.

The prior art US 2007/0083467 (Al) discloses a method for encrypting media data by encrypting blocks of data according to an encryption parameter which serves to specify portions of media data within the blocks that is to be encrypted. It is also worth mentioning that in the prior art, the controller in a portable media device is responsible to obtain a cryptographic key and encryption parameters associated with the media file and decrypt the portion of the media data which has been encrypted. The unauthorized user will not be able to view part of the media content as the partial encryption has rendered the media content substantially unusable by the unauthorized users.

The prior arts however did not address the solution for setting a limitation to the user to access the media content. It is important that the media content can only be accessed by user with the correct password and within allowable range so that the media content is protected appropriately.

Summary of the invention It is an objective of the present invention to protect the media content by encrypting the media content.

It is another objective of the present invention to generate a limitation parameter based on allowable range of frequency, date or time.

It is further an objective of the present invention to generate security means by using the limitation parameter and a user password as the inputs in a key derivation function. It is also an objective of the present invention to encrypt the attribute data and storing the encrypted attribute data in an encryption extension block. It is further another objective of the present invention to modify the attribute data in media content.

It is another objective of the present invention to encrypt the media content by replacing the attribute data with a modified attribute data.

It is also an objective of the present invention to generate an identifier for the attribute data for easy comparison of different attribute data. It is further an objective of the present invention to decrypt the encrypted media content.

It is another objective of the present invention to retrieve the allowable range of limitation parameter. For example, frequency, date information or time information from the media content.

It is another objective of the present invention to decrypt the encrypted colour lookup table using a security means. It is also an objective of the present invention to decrypt the media content by replacing the modified attribute data with the decrypted attribute data.

The present invention discloses a method for encrypting media content, a method for modifying attribute data and a method for decrypting the media content.

The method for encrypting media content according to the present invention comprises the steps of replacing and encrypting an attribute data and replacing it with a modified attribute data. In another embodiment of the present invention, the method for decrypting the media content comprises the steps of replacing the modified attribute data with the decrypted attribute data and loading the full media content if the password keyed in by the user is correct and the limitation parameter is still within allowable range, whereas if the password is not correct or the limitation parameter is not within the allowable range, the media content will not be displayed in full.

A further embodiment of the present invention describes a method which involves modifying the attribute data according to a selected modification type. Brief description of drawings

Figure 1 illustrates an overview of the present invention. Figure 2 illustrates a process flow for the method of encrypting media content in accordance to the present invention.

Figure 3 illustrates a process flow for the method of modifying attribute data in accordance to the present invention.

Figure 4 illustrates a process flow for the method of decrypting the media content in accordance to the present invention.

Figure 5 illustrates a process flow for an example of encrypting colour lookup table in a preferred embodiment in accordance to the present invention.

Figure 6 illustrates a process flow for an example of modifying a colour lookup table in a preferred embodiment in accordance to the present invention. Figure 7 illustrates a process flow for an example of decrypting colour lookup table in a preferred embodiment in accordance to the present invention.

Detailed Description Described below are preferred embodiments of the present invention with reference to the accompanying drawings. The configuration of the invention is not limited to the configuration mentioned in the following description.

Referring to figure 1, the figure shows an overview of the present invention. The media content comprises multiple information blocks for storing the respective information. For instance, there are at least an image block, graphic control extension block, comment extension block and etc. The present invention involves steps of encrypting an attribute data (13). The attribute data block (11) is responsible for storing the original attribute data (13). After the modification on the attribute data (13), the modified attribute data (27) is then stored in the modified attribute data block (12). Another information block involved in the present invention is the encryption extension block (15). The encryption extension block (15) is responsible for storing the encrypted attribute data (26) and also a calculated attribute data identifier (14). The encrypted attribute data (26) and identifier (14) are then retrieved from the encryption extension block (15) during the decryption of the media content. An attribute data (13) is referred to a feature in a media content, which is directly or indirectly affecting the quality of the media content loaded. The media content comprises a graphic, video, audio or a combination thereof. Referring to figure 2, the figure illustrates a process flow for the method of encrypting media content in accordance to the present invention. The attribute data (13) of the media content is first modified. Then a marker for the input media content is created .

A mathematical function, preferably a sigmoid function, is used to generate a limitation parameter (21). The limitation parameter (21) is generated based on an allowable range of any one or a combination of frequency, date information or time information.

A password-based key derivation function 2 (PBKDF-2) is used to generate a security means (22). The limitation parameter (21) and a user password (23) which is retrieved from the marker are used as the inputs during the generation of the security means (22). The security means (22) comprises of a key, initialization vector (IV) or a combination thereof. The initialization vector (IV) is a non-repeating random number used only once and used along the key to enhance the security in the media content encryption.

Simultaneously, the first identifier (24) for the attribute data (25) of the media content is generated. The first identifier (24) will then be used for comparison purpose during the decryption of the media content. The attribute data (25) is then encrypted by using the security means (22).

Subsequently, the first identifier (24) generated and the encrypted attribute data (26) are then stored into an encryption extension block (15) in the media content. The attribute data (13) in the media content is then replaced by the modified attribute data (27).

Referring to figure 3, the figure illustrates a process flow for the method of modifying the attribute data (13). An attribute data (13) is obtained from the original media content. The user will select a predetermined type of modification. The selection will determine the quality of the media content loaded to the unauthorized users. The attribute data will then be modified according to the selected modification type. Referring to figure 4, the figure illustrates a process flow for the method of decrypting media content in accordance to the present invention. The marker file for the media content will be checked. The limitation parameter (21) attached to the media content is then retrieved. Subsequently, the user password (23) is interpreted and a second security means (43) is generated using the user password (23) and the retrieved limitation parameter (21) as the inputs. Using the second security means (43), the encrypted attribute data (26) is decrypted.

The first identifier (24) is then retrieved from the encryption extension block (15) and the second identifier (44) is generated based on the decrypted attribute data (45). Both of the identifiers are then compared. The media content will then be loaded with the modified attribute data (27) when the first identifier (24) not matching the second identifier (44). Should both the identifiers matches, the modified attribute data (27) will be replaced with the decrypted attribute data (45) and the media content is subsequently loaded with the decrypted attribute data (45).

Example 1

It is a preferred embodiment in accordance to the present invention that the attribute data is a colour lookup table. The corresponding information blocks would therefore be colour lookup table block and modified colour lookup table block.

Referring to figure 5, the figure illustrates a process flow for the method of encrypting media content involving the colour lookup table (51), particularly video or images in accordance to the present invention. The colour lookup table (51) of the media content is first modified. Then a marker for the input media content is created. A mathematical function, preferably a sigmoid function, is used to generate a limitation parameter (21). The limitation parameter (21) is generated based on an allowable range of any one or a combination of frequency, date information or time information.

A password-based key derivation function 2 (PBKDF-2) is used to generate a security means (22). The limitation parameter (21) and a user password (23) which is retrieved from the marker are used as the inputs during the generation of the security means (22). The security means (22) comprises of a key, initialization vector (IV) or a combination thereof. Simultaneously, the first identifier (24) for the colour lookup table (52) of the media content is generated. The first identifier (24) will then be used for comparison purpose during the decryption of the media content. The colour lookup table (52) is then encrypted by using the security means (22).

Subsequently, the first identifier (24) generated and the encrypted colour lookup table (53) are then stored into an encryption extension block (15) in the media content. The colour lookup table (51) in the media content is then replaced by the modified colour lookup table (52). Referring to figure 6, the figure illustrates a process flow for the method of modifying the colour lookup table (51). A colour lookup table (51) and its offset are first obtained from the media content. The user then selects the type of modification preferable. Should the user wish the graphic to have visible shape, the colour components will be modified to the RGB, YUV or YC _b C _r components. The user can then select the type of image from a provided template. Subsequently, the original colour lookup table (51) is replaced with the modified colour lookup table (52) . Alternatively, the user can also choose to have the graphic not having visible shape. All the bytes which display different colours will be replaced by a single value which displays only monotone graphics.

Referring to figure 7, the figure illustrates a process flow for the method of decrypting media content involving the colour lookup table (51), particularly video or images in accordance to the present invention. The marker file for the media content will be checked. The limitation parameter (21) attached to the media content is then retrieved. Subsequently, the user password (23) is interpreted and a second security means (43) is generated using the user password (23) and the retrieved limitation parameter (21) as the inputs. Using the second security means (43), the encrypted colour lookup table (53) is decrypted. The first identifier (24) is then retrieved from the encryption extension block (15) and the second identifier (44) is generated based on the decrypted colour lookup table (71). Both of the identifiers are then compared. The media content will then be loaded with the modified colour lookup table (52) when the first identifier (24) not matching the second identifier (44). Should both the identifiers matches, the modified colour lookup table (54) will be replaced with the decrypted colour lookup table (71) and the media content is subsequently loaded with the decrypted colour lookup table (71). In as much as the present invention is subject to many variations, modifications and changes in detail, it is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.