Nippon Telegraph and Telephone Corporation

Nippon Telegraph and Telephone Public Corporation

Youichi Takashima

Hiroshi Ogawa

Takao Nakamura

Atsuki Tomioka

Masayuki Kanda

Kiyoshi Yamanaka

Kazumaro Aoki

Kazuo Ohta

Shiho Moriai

Hiroki Ueda

Tsutomu Matsumoto

Shinji Ishii

A method for embedding a watermark into digital data, when the watermark is to be embedded in a digital image, independently changes real number components and imaginary number components of each of coefficient values of a complex watermark coefficient matrix using key, from the watermark to be embedded in the digital image, a step for performing a discrete Fourier inverse transform on the sequence matrix of the changed watermark and generating a watermark pattern; and a step for adding like tiling the water mark pattern to the original image, and generating an embedded image. Further more, a watermark detection method for detecting a watermark from a digital data, a step for separating a block from an arbitrary position on the detected object image, a step for performing a discrete Fourier transform on the block and obtaining a sequence matrix, a step for generating position information for a component that is to be detected and that is specified by the key, a step for detecting a position marker sequence by calculating a phase difference of a sequence by an amount of parallel displacement, for each item of the position information, and extracting offset information which is the amount of parallel displacement when there is agreement between a start point of an embedded watermark and a start point of the block cut from the detected object image, and a step for detecting the embedded watermark cut from the detected object image.

Digital watermark embedding method, digital watermark embedding apparatus, and storage medium storing a digital watermark embedding program

A method for embedding a watermark into digital data by independently changing real and imaginary number components of the coefficient values of a complex watermark coefficient matrix using a key, performing a discrete Fourier inverse transform on the sequence matrix of the changed watermark and generating a watermark pattern, adding like tiling the water mark pattern to the original image, and generating an embedded image. A watermark detection method includes separating a block from an arbitrary position on the detected object image, performing a discrete Fourier transform on the block and obtaining a sequence matrix, generating position information for a component which is to be detected and is specified by the key, detecting a position marker sequence by calculating a phase difference of a sequence by a parallel displacement, for the position information, extracting offset information, and detecting the embedded watermark from the detected object image.

A method for embedding digital watermark data in digital data contents includes the steps of obtaining a frequency coefficient of block data of digital data contents, obtaining a complexity of the block data, obtaining an amount of transformation of the frequency coefficient from the complexity and the digital watermark data, and embedding the digital watermark data by transforming the frequency coefficient. In addition, a method for reading digital watermark data includes the steps of calculating a probability of reading '1' or '0' in a read bit sequence by using a test method on the basis of binary distribution, determining the presence or absence of digital watermark data according to the probability, and reconstituting digital watermark data. Another method includes the steps of performing soft decision in code theory by assigning weights to the digital watermark sequence with a weighting function, and reconstituting digital watermark data.

Method and apparatus for digital watermarking

In the evaluation of the randomness of an S-box, measures of resistance to higher order cryptanalysis, interpolation cryptanalysis, partitioning cryptanalysis and differential-linear cryptanalysis and necessary conditions for those measures to have resistance to each cryptanalysis are set, then for functions as candidates for the S-box, it is evaluated whether one or all of the conditions are satisfied, and those of the candidate functions for which one or all of the conditions are satisfied are selected as required. It is also possible to further evaluate the resistance of such selected functions to at least one of differential cryptanalysis and linear cryptanalysis and select those of the candidate functions which are resistant to at least one of the cryptanalyses as required.

Method and apparatus for evaluating the strength of an encryption

A method for embedding a watermark into a digital image. The method includes independently changing real number components and imaginary number components of each of coefficient values of a complex watermark coefficient matrix using a key, from the watermark to be embedded in the digital image. The method further includes a step for performing a discrete Fourier inverse transform on the sequence matrix of the changed watermark and generating a watermark pattern. The method also includes a step for adding like tiling the water mark pattern to the original image, and generating an embedded image.

A plurality of round processing parts ( ) are provided each of which contains a nonlinear function part ( ), and each nonlinear function part ( ) comprises: a first key-dependent linear transformation part ( ) which performs a linear transformation based on a subkey; a splitting part ( ) which splits the output from the first key-dependent linear transformation part into n pieces of subdata; a first nonlinear transformation part ( ) which nonlinearly transforms those pieces of subdata, respectively; a second key-dependent linear transformation part ( ) which linearly transforms those nonlinearly transformed outputs based on a subkey and outputs n pieces of transformed subdata; a second nonlinear transformation part ( ) which nonlinearly transforms those transformed subdata; and a combining part ( ) which combines the nonlinearly transformed outputs. An n&times;n matrix, which represents the linear transformation in the second key-dependent linear transformation part ( ), is formed by n vectors whose Hamming weights are equal to or larger than T&minus;1 for a security threshold T, thereby increasing the invulnerability against differential cryptanalysis and linear cryptanalysis.

Data converter and recording medium on which program for executing data conversion is recorded

A message delivery system which can guarantee the authenticity of a user, the reliability of a message delivery, and the authenticity of the message delivery, while preventing an illegal act, and which can prove them at a later time. The system has an information provider terminal including a user authentication unit for carrying out a user authentication of the user according to a zero knowledge interactive proof protocol using check bits E generated according to a work key W, and a transmission unit for transmitting to the user a ciphertext C in which a message M to be delivered to the user is enciphered according to a secret key cryptosystem by using the work key W, and the check bits E. The system also has a user terminal including a message reception unit for taking out the work key W by using at least the check bits E, and obtaining the message M by deciphering the ciphertext C according to the secret key cryptosystem by using the work key W.

Method and system for message delivery utilizing zero knowledge

A digital information protection scheme using an improved security protocol. In a system in which a user makes an access to a digital information provided by an information center by connecting a computer card owned by the user to an information terminal device connected with the information center, a work key for encrypting a desired digital information is delivered from the information center to the computer card through the information terminal device, and the work key is registered in the computer card; the desired digital information encrypted by the work key is delivered from the information center to the information terminal device; and an encrypted digital information delivered from the information center is decrypted at the information terminal device by using the work key registered in the computer card, and a decrypted digital information is provided to the user at the information terminal device.

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Yokohama, Japan

Youichi Takashima