Classifications

• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
  • G06T1/00—General purpose image data processing
  • G06T1/0021—Image watermarking
  • G06T1/005—Robust watermarking, e.g. average attack or collusion attack resistant
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
  • H04N1/32—Circuits or arrangements for control or supervision between transmitter and receiver or between image input and image output device, e.g. between a still-image camera and its memory or between a still-image camera and a printer device
  • H04N1/32101—Display, printing, storage or transmission of additional information, e.g. ID code, date and time or title
• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
  • G06T2201/00—General purpose image data processing
  • G06T2201/005—Image watermarking
  • G06T2201/0051—Embedding of the watermark in the spatial domain
• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
  • G06T2201/00—General purpose image data processing
  • G06T2201/005—Image watermarking
  • G06T2201/0061—Embedding of the watermark in each block of the image, e.g. segmented watermarking
• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
  • G06T2201/00—General purpose image data processing
  • G06T2201/005—Image watermarking
  • G06T2201/0063—Image watermarking in relation to collusion attacks, e.g. collusion attack resistant
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N2201/00—Indexing scheme relating to scanning, transmission or reproduction of documents or the like, and to details thereof
  • H04N2201/32—Circuits or arrangements for control or supervision between transmitter and receiver or between image input and image output device, e.g. between a still-image camera and its memory or between a still-image camera and a printer device
  • H04N2201/3201—Display, printing, storage or transmission of additional information, e.g. ID code, date and time or title
  • H04N2201/3225—Display, printing, storage or transmission of additional information, e.g. ID code, date and time or title of data relating to an image, a page or a document
  • H04N2201/3233—Display, printing, storage or transmission of additional information, e.g. ID code, date and time or title of data relating to an image, a page or a document of authentication information, e.g. digital signature, watermark
  • H04N2201/3235—Checking or certification of the authentication information, e.g. by comparison with data stored independently
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N2201/00—Indexing scheme relating to scanning, transmission or reproduction of documents or the like, and to details thereof
  • H04N2201/32—Circuits or arrangements for control or supervision between transmitter and receiver or between image input and image output device, e.g. between a still-image camera and its memory or between a still-image camera and a printer device
  • H04N2201/3201—Display, printing, storage or transmission of additional information, e.g. ID code, date and time or title
  • H04N2201/3225—Display, printing, storage or transmission of additional information, e.g. ID code, date and time or title of data relating to an image, a page or a document
  • H04N2201/3233—Display, printing, storage or transmission of additional information, e.g. ID code, date and time or title of data relating to an image, a page or a document of authentication information, e.g. digital signature, watermark
  • H04N2201/3236—Details of authentication information generation

Definitions

• This invention pertains to methods and systems for finge ⁇ rinting digital data.
• DSSS Direct Sequence Spread Spectrum
• Unique finge ⁇ rinting words are defined where each includes at least one spread sequence.
• a finge ⁇ rinting word comprises a plurality symbols, called 'T symbols.”
• Each T symbol is composed of 2c- 1 blocks, where c represents the number of colluders that are desired to be protected against.
• Each block contains d spread sequence chips.
• the finge ⁇ rinting words are assigned to a plurality of entities to which protected objects embedded with the finge ⁇ rinting words are to be distributed.
• Fig. 3 is a table that contains a plurality of values that are assignable to various users in connection with the described embodiment.
• Fig. 5 is a flow diagram that describes steps in a detection method in accordance with the described embodiment.
• Each T symbol for a user's unique fmge ⁇ rint is then compared with the set for each corresponding T-symbol in the matrix and a count is kept of the number of times each user's T symbol coincides with a T-symbol that is found in a particular set.
• the user with the highest count is selected as a colluder that produced the altered object.
• a number of program modules may be stored on the hard disk 144, magnetic disk 148, optical disk 152, ROM 138, or RAM 140, including an operating system 158, one or more application programs 160, other program modules 162, and program data 164.
• a user may enter commands and information into computer 130 through input devices such as a keyboard 166 and a pointing device 168.
• Other input devices may include a microphone, joystick, game pad, satellite dish, scanner, or the like.
• These and other input devices are connected to the processing unit 132 through an interface 170 that is coupled to the bus 136.
• a monitor 172 or other type of display device is also connected to the bus 136 via an interface, such as a video adapter 174.
• personal computers typically include other peripheral output devices (not shown) such as speakers and printers.
• Computer 130 commonly operates in a networked environment using logical connections to one or more remote computers, such as a remote computer 176.
• the remote computer 176 may be another personal computer, a server, a router, a network PC, a peer device or other common network node, and typically includes many or all of the elements described above relative to computer 130, although only a memory storage device 178 has been illustrated in Fig. 1.
• the logical connections depicted in Fig. 1 include a local area network (LAN) 180 and a wide area network (WAN) 182.
• LAN local area network
• WAN wide area network
• the data processors of computer 130 are programmed by means of instructions stored at different times in the various computer-readable storage media of the computer.
• Programs and operating systems are typically distributed, for example, on floppy disks or CD-ROMs. From there, they are installed or loaded into the secondary memory of a computer. At execution, they are loaded at least partially into the computer's primary electronic memory.
• the invention described herein includes these and other various types of computer-readable storage media when such media contain instructions or programs for implementing the steps described below in conjunction with a microprocessor or other data processor.
• the invention also includes the computer itself when programmed according to the methods and techniques described below.
• Each finge ⁇ rinting word is divided into a number of blocks that, in turn, include a plurality of bits.
• Each of the blocks includes, in this example, four bits.
• the matrix that is defined by the finge ⁇ rinting word assignments is known as a "T-code". As there can be many, many users, the T-code necessary to provide finge ⁇ rinting words for all of the users will be quite large.
• a single permutation of the columns of the T-code is performed before embedding an object with a fmge ⁇ rint word.
• An exemplary permutation is shown in Table 1 below where the order of the blocks is changed. For simplicity, the permutation as represented in the table above occurs over whole blocks. In reality, the permutation occurs at the bit level. For example, the column of leftmost bits might be moved to bit position 12. This permutation is uniform for all of the users and is known only to the encoder or embedder and the decoder:
• the notation x-ll denotes the restriction of word x to the bit locations of I
• W(x) denote the Hamming weight of the string x.
• the Hamming weight of a binary string of 1 's and 0's is the number of 1 's in the string.
• the string is composed of +l 's and -l 's, we could define it to be the number of +l 's in the string.
• a unique aspect of user l 's finge ⁇ rinting word in Fig. 2 is that block 0 comprises all 1 's. Each of the other users has all 0's in their corresponding block 0.
• the marking assumption which states that users cannot modify "unseen” bits
• none of the bits in block 0 will be modified. Accordingly, all of the bits in block 0 will be 0 and user 1 can be ruled out as a colluder.
• any of the bits in block 0 of the altered object x are determined to be 1, then user 1 can be incriminated as a colluder.
• the algorithm looks for this unique step function or some semblance thereof for users other than the first and last users. For the first and last users, the algorithm simply looks for the unique bits in the blocks that are unique for the first and last users. When a step function (or unique bits) are located, a corresponding user can be incriminated. In this example, since the step function still exists for user 3, user 3 can be incriminated. This can be mathematically represented as follows ( ⁇ is the incrimination error probability):
• the second algorithm of the BS-system is directed to incriminating a user or colluder without having to use such a large T-code.
• c represent the number of colluders that are desired to be defended against.
• a T-code is then selected to have 2c rows. In this system each row is also referred to as a "color”. So, for example, if one wants to defend against 20 colluders, then a T-code is selected that has 40 rows or colors.
• Each row or color in the T-code comprises a plurality of blocks that make up a T-symbol.
• Each color or T-symbol is treated as a letter in an alphabet that is defined by the T-code
• the letters in the alphabet are then used to build unique finge ⁇ rinting words for each of the users of the protected object That is, finge ⁇ rmting words contain L colors or T-symbols, where L is a number that is selected to be large enough so that, given the number of users that are to be assigned finge ⁇ rinting words, each is assured of being assigned a unique finge ⁇ rinting word.
• Each of the protected objects are embedded with a permuted form of one of the finge ⁇ rinting words. Now, when an altered object is found, applying the principles of Algorithm 1 to each of the T symbols in the altered object will yield a set of colors or T-symbols that are likely the subject of a collusion.
• the length in bits of the finge ⁇ rinting word or sequence is given by the following equation: O(c 4 log(N/ ⁇ ) log(l/ ⁇ )), where "c" is the size of the collusion, "N” is the number of users, and ⁇ is the incrimination error probability.
• c is the size of the collusion
• N is the number of users
• ⁇ is the incrimination error probability.
• aspects of the BS- system are exploited in conjunction with the use of spread spectrum technology.
• a spread spectrum sequence is associated with individual blocks of individual finge ⁇ rint words.
• the spread spectrum sequence utilizes a data structure called a "chip" that is embedded in the protected object.
• the use of spread sequences in the embedding process enables redefinition of the relative weight of each block as well as redefinition of a working range (defined below).
• the new weights and working range are utilized in connection with an analysis that increases the robustness of the protectiveness over that of conventional methods and systems provide.
• Spread spectrum chips x - (xj, ...xj are utilized that have values that are measured in the same units as the individual components of the protected object vector, but which have values that are small in comparison to the values that the individual vector components can have, e.g. the chips have values that are in ⁇ +1, -1 ⁇ . That is, values of x are selected to be small enough that when they are added to m they are difficult if not impossible to detect.
• a spread sequence can be utilized to embed data symbols that are in ⁇ +1, -
• a "chip” is the smallest of the data structures and refers to a spread spectrum chip.
• the data symbols that are embedded through the use of the spread spectrum chips are in ⁇ +D, -D ⁇ .
• a "block” is composed of d chips, where d represents a parameter that controls the error rate.
• the Is complement of block C, is denoted C',.
• a "T-symbol” comprises a plurality of blocks. In the described embodiment, a T-symbol is composed of 2c- 1 blocks, where c represents the number of colluders that are desired to be defended against.
• Last of the data structures is the finge ⁇ rinting word which is composed of L T-symbols, where L represents a particular number that is selected to ensure that all of the users in the relevant user universe receive unique finge ⁇ rinting words.
• each user is first assigned a unique fmge ⁇ rinting word.
• the finge ⁇ rinting words inco ⁇ orate a spread sequence rather than the individual bits as in the BS-system.
• each block B, of the T code in the BS-system is replaced with a suitable spread sequence.
• blocks that are supposed to be a l d in the BS-system are replaced with C
• blocks that are supposed to be 0 d are replaced with the Is complement C',.
• An exemplary T code in accordance with this embodiment is shown in Fig. 3.
• the columns of the T code are permuted (at the chip level) as discussed above.
• An object can now be finge ⁇ rinted with the finge ⁇ rinting words that are defined by the permuted T code.
• Fig. 4 shows a flow diagram that describes steps in an embedding method in accordance with the described embodiment.
• Step 100 builds or defines a suitable T-code, an exemplary one of which is shown in Fig. 3.
• Step 102 permutes the columns of the T-code in a manner that is known only to the embedder and the decoder that will ultimately decode the finge ⁇ rints. Permutation of the columns can take place by randomly shuffling the chips for all of the users (the same permutation for all the users). The permutation is the same for all of the users. An example of a suitable permutation was given above.
• step 104 embeds a unique finge ⁇ rinting word in each of a number of different objects that are desired to be protected.
• An example of an embedding process is given just below After the embedding process, the protected objects can be distributed.
• a first step in the detection process when an object is received is to unpermute the columns that were previously permuted
• the columns (at the chip level) of the T-code are randomly permuted. Both the embedder and the detector know the random permutation.
• the chips are detected in the received object.
• Each component, e.g. pixel, a is compared with the expected unflnge ⁇ nted component, e.g. pixel, m,
• We use z to denote the detected chip i. This may differ from the original chip x confine due to attacks.
• Fig. 5 shows a flow diagram that describes steps in a weight assignment and clipping method in accordance with the described embodiment, an example of which is given directly above.
• Step 200 gets the first block that is present in a finge ⁇ rinting word.
• Step 202 calculates the weight of the first block. In the described embodiment, the weight of a given block is calculated as set forth above.
• Step 204 determines whether the block is likely an "unseen” block and if so, step 206 clips the block's weight to its working range value. If the block is likely "seen", then its weight is as calculated above (step 208).
• Step 210 determines whether there are any additional blocks. If so, the method branches back to step 202.
• a T-code having a reduced size was defined when the size of the T-code was considered in light of the number of colluders that were to be defended against.
• each new row or color of the T-code defined a T-symbol, and multiple T-symbols were used to build finge ⁇ rinting words for all of the users.
• Each of the finge ⁇ rinting words were different and unique.
• the permuted forms of the finge ⁇ rinting words are used for embedding in an object to be protected.
• Each of the finge ⁇ rinting words when unpermuted and analyzed in accordance with the BS-system's second algorithm yielded a user that likely constituted a colluder.
• a reduced-size T-code is also defined and includes a plurality of colors or rows.
• the number of colors or rows is a function of the number of colluders c that are desired to be defended against. That is, the number of colors or rows is defined, in this example, to be 2c.
• Each color or row defines a T-symbol.
• the T-symbols that are being defined here are, however, very different from the T-symbols that are defined in the BS-system.
• the presently-described T-symbols that make up the T-code each contain spread sequences, rather than collections of bits.
• a finge ⁇ rinting word is composed of L T-symbols, where a T- symbol is composed of 2c-I blocks.
• a block is composed of d chips, where a chip is a spread spectrum chip. Given this relationship, the size of a vector that represents the protected object is 2dcL.
• the columns are randomly permuted in a manner that is known to both the embedder and the detector. After permutation of the columns, individual objects that are desired to be protected are embedded with a permuted finge ⁇ rinting word that uniquely serves to identify an associated user or entity.
• the manipulated or altered finge ⁇ rinting word contains L T-symbols.
• each of the individual constituent T-symbols in the altered finge ⁇ rinting word is analyzed and a set of one or more likely colors that might be the subject of a collusion is built.
• Step 308 then gets the first user's finge ⁇ rinting word and step 310 evaluates the user's finge ⁇ rinting word by comparing the first T-symbol in the user's finge ⁇ rinting word with a set of one or more colors from the matrix.
• the matrix has L columns, each of which corresponds to a different T- symbol of a fmge ⁇ rinting word. For any one column, there is a set of one or more colors that are produced by Algorithm 3.
• step 320 determines whether there are any additional users. If there are additional users, then the method loops back to step 308 and gets the new user's finge ⁇ rinting word. If there are no additional users, then step 322 selects the user with the highest counter value and incriminates them as a colluder.
• each finge ⁇ rinting word has a length L that, in this example, is five T-symbols long.
• Applying Algorithm 3 to each of the five T-symbols might yield the following matrix:
• each of the last five columns corresponds to an individual T-symbol in the altered finge ⁇ rinting word and contains a number of "X" marks.
• Each "X" indicates, for a particular T-symbol, a color that might be the subject of a collusion.
• Each T-symbol in the altered finge ⁇ rinting word has a set of one or more colors associated with it. In this example, for the first T-symbol in the altered finge ⁇ rinting word, colors 2 and 3 might be the subject of the collusion. For the second T-symbol in the finge ⁇ rinting word, colors 1 and 5 might be the subject of the collusion, and so on.
• each user's finge ⁇ rinting word is compared, T-symbol by T-symbol, with the implicated colors for each of the corresponding T-symbols in the matrix. This comparison is summarized in the table that appears below:

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