摘要:
Improved techniques for making copy detection patterns and using them to detect copying relationships between digital representations. The techniques include techniques for including a message in a copy detection pattern without altering the copy detection patterns entropy and reading the message, techniques for using a copy detection pattern on an analog form to determine whether the analog form is an original analog form without reference to a digital representation of the original of the analog form's copy detection pattern, techniques for increasing the sensitivity of copy detection using copy detection patterns by modifying one of two copy detection patterns that are being compared to take into account alterations resulting from the copying process, techniques for distributing a copy detection pattern across a document, and techniques for using the entropy of a copy detection pattern to locate the copy detection pattern. Also disclosed are applications of copy detection patterns with copying that involves transformations between the digital and analog forms and with digital-to-digital copying.
摘要:
Techniques for determining authenticity of analog forms such as packaging or documents (117). One of the techniques determines whether the analog form has been made directly from a digital representation (903) or by photocopying or scanning an analog form. The technique makes the determination by comparing (911) an original digital representation of a portion of the analog form with a digital recording (203) of the portion from the analog form and measuring differences in features that are affected by the operations of photocopying or scanning. The original digital representation (105) and the analog form may have a “noisy”, i.e., random or pseudo random pattern. Such noisy patterns may further be used for other authentication purposes, such as determining whether the portion of the analog form that has the noisy pattern has been altered and to carry hidden messages. The noisy pattern may carry a logo or may be part or all of a barcode.
摘要:
An apparatus for estimating a wireless radio channel between a first terminal and a relay station, the apparatus including a receiver for receiving a signal including a superposition of previously transmitted first information from the first terminal and second information from a second terminal, the second terminal also communicating with the relay station, a storage for storing the previously transmitted first information, and a channel calculator for calculating the wireless radio channel using the received signal and the stored first information as pilot information for the received signal.
摘要:
The computational cost of embedding information in a digital representation is reduced by making a set of at least two copies of the digital representation and altering subdivisions of the copies so that corresponding subdivisions in the copies are distinguishable from each other. The subdivisions may be arbitrary or may be functional subdivisions of the digital representation. The subdivisions may be distinguishable by features such as watermarks that do not affect the way in which the digital representation is normally used. The marked copy in which the information is embedded is then made by selecting a given subdivision in the marked copy from one of the set of copies. Selection may be done using a selection string that has an element for each subdivision. The value of the element indicates which of the set of digital representations the subdivision corresponding to the element is to be selected from. The result of this procedure is a sequence of distinguishable subdivisions in the marked copy, and the sequence carries the embedded information. Each marked copy may have a unique sequence, in which case the sequence functions as a fingerprint for the copy. The sequence may also encode information. Examples are an identification of the recipient of the copy, information about the transaction that resulted in the copy being made, or encoded information about the content of the marked copy.
摘要:
A stepper motor device has a stator and a rotor. The rotor comprises: a shaft; a rotor core associated with the shaft; and a magnet fixed to the rotor core. The stator comprises: a stator shell; a yoke disposed within the shell; a coil wound about the yoke and an end plate magnetically connecting the yoke to the stator shell. The coil is located beside the magnet in the axial direction of the motor. The stator has a number of salient poles, and the salient poles are arranged to face the magnet across a small air gap. The coil creates magnetic poles in the salient poles with a common polarity.
摘要:
A method and system for processing content are described including generating a dummy value, inserting the dummy value into encoded content, selecting a position in the encoded content where the dummy value in the encoded content is to be replaced by a real value, generating the real value and replacing the dummy value with the real value in the encoded content.
摘要:
Techniques for protecting the security of digital representations and of analog forms made from them, including a technique for authenticating an analog form produced from the digital representation, an active watermark that contains program code that may be executed when the watermark is read, and a watermark agent that reads watermarks and sends messages with information concerning the digital representations that contain the watermarks. A watermark agent may be a permanent resident of a node in a network or of a device or it may move from one network node to another. The watermark agent executes code which examines digital representations residing in the node or device for watermarked digital representations that are of interest to the watermark agent. The watermark agent then sends messages which report the results of its examination of the digital representations. If the watermarks are active, the agent and the active watermark may cooperate.
摘要:
Three new obfuscation techniques. Data field obfuscation replaces references to data fields that use an object name and a field name with references that use an object name but do not use a field name. Obfuscation using the reflection mechanism for the executable code works by replacing a construct in the executable code with one or more equivalent constructs made using the reflection mechanism. Obfuscation of externally-defined constructs is done by relating the externally-defined construct to an obfuscation for the construct that is used within the executable code. The relationship is defined in a portion of the executable code, and at least the externally-fined construct is encrypted in the portion. The various obfuscation techniques may be used with each other or with other previously-known obfuscation techniques. The disclosed obfuscation techniques are particularly well-adapted for use with the byte codes produced by Java language compilers from Java language programs.