Abstract: In one embodiment, a method includes receiving at a stylus a receive signal from a device. The stylus includes one or more computer-readable media embodying logic, and the device includes a touch sensor. The receive signal is received at the stylus through the touch sensor of the device and one or more electrodes of the stylus. The method includes filtering the receive signal for processing by the logic and processing, by the logic, the receive signal as filtered.

Abstract: In one embodiment, a stylus receives a first signal from a first electrode of the stylus, the stylus being operable to communicate wirelessly with a device through a touch sensor of the device; receives a second signal from a second electrode of the stylus, the second signal being a reference signal and the second electrode being a reference electrode; and compares the first signal with the second signal.

Abstract: A communication system including a transmitter, a receiver, and a serial link (for example, a TMDS-like link) in which video data (or other data) are encrypted, the encrypted data are transmitted from the transmitter to the receiver, and the transmitted data are decrypted in the receiver, a transmitter and a receiver for use in such systems, a cipher engine for use in such a transmitter or receiver, a method for operating such a transmitter or receiver to encrypt or decrypt data, and a method for authenticating a receiver prior to transmission of encrypted data to the receiver over a serial link. Each transmitter, receiver, and cipher engine is configured to implement a content protection protocol in a manner that implements at least one and preferably more than one of a class of attack prevention features disclosed herein.

Abstract: In preferred embodiments, a cryptographic device in which two key sets are stored: a normal key set (typically unique to the device) and a test key set (typically used by each of a relatively large number of devices). The device uses the normal key set in a normal operating mode and uses the test key set in at least one test mode which can be a built-in self test mode. Alternatively, the device stores test data (e.g., an intermediate result of an authentication exchange) in addition to or instead of the test key set. In other embodiments, the invention is a cryptographic device including a cache memory which caches a portion of a key set for performing an authentication exchange and/or at least one authentication value generated during an authentication exchange. Other embodiments of the invention are systems including devices that embody the invention and methods that can be performed by systems or devices that embody the invention.

Abstract: A system for implementing a content protection protocol to encrypt data, including transmitters and receivers to which key selection vectors of a vector set have been distributed, wherein a subset of the key selection vectors in the vector set has not been distributed to any of the transmitters or any of the receivers, and a method for enabling transmitters and receivers to implement a content protection protocol including by distributing key selection vectors of a vector set, and private key sets, to the transmitters and receivers while reserving a subset of the key selection vectors of the vector set.

Abstract: In some embodiments, the invention is a personal digital network (“PDN”) including hardware (sometimes referred to as Ingress circuitry) configured to transcrypt encrypted content that enters the PDN. Typically, the transcryption (decryption followed by re-encryption) is performed in hardware within the Ingress circuitry and the re-encryption occurs before the decrypted content is accessible by hardware or software external to the Ingress circuitry. Typically, transcrypted content that leaves the Ingress circuitry remains in re-encrypted form within the PDN whenever it is transferred between integrated circuits or is otherwise easily accessible by software, until it is decrypted within hardware (sometimes referred to as Egress circuitry) for display or playback or output from the PDN.

Abstract: A method, apparatus and system for pre-authenticating ports is disclosed. In one embodiment, an active port facilitating communication of media content between a transmitting device and a receiving device is identified, while the active port are associated with a first High-Definition Content Protection (HDCP) engine. Then, inactive ports that are in idle mode serving as backup ports to the active port are identified, while the inactive ports are associated with a second HDCP engine. Pre-authentication of each of the inactive ports is performed so the pre-authenticated inactive ports can subsequently replace the active port if a port switch is performed.

Abstract: A communication system including a transmitter, a receiver, and a TMDS-like link, in which video data and auxiliary data (typically including timing data associated with other auxiliary data) are transmitted from the transmitter to the receiver, or in which video data are transmitted over the link from the transmitter to the receiver, and auxiliary data (typically including timing data associated with other auxiliary data) are transmitted from the receiver to the transmitter. In typical embodiments the auxiliary data include one or more streams of audio data.

Abstract: An integrated circuit that includes operational circuitry and message digest generation circuitry coupled to the operational circuitry, a method for testing an integrated circuit including message digest generation circuitry, and a system including an integrated circuit (which includes message digest generation circuitry) and at least one external device coupled to the integrated circuit. The message digest generation circuitry is coupled and configured to generate at least one digest of at least one message, where each message is indicative of at least one aspect of the integrated circuit's state. For example, a message can be a sequence of voltages or logic levels sampled at a specific sequence of nodes of operational circuitry of the integrated circuit.

Abstract: In a class of embodiments, the invention is an open computing system (e.g., a PC) in which a protected, closed subsystem is embedded. The closed subsystem typically includes multiple parts that ensure that content protection keys and protected content are never revealed outside the closed subsystem. Content (e.g., high-definition digital video) that enters the closed subsystem (and is typically decrypted and re-encrypted within the closed subsystem) is afforded a similar level of protection within the open system as can be obtained in standalone closed systems. Other aspects of the invention are methods for protecting content within an open computing system, a closed system (or disk drive thereof) configured to be embedded in an open computing system, and circuitry configured to be embedded in an open computing system for combining the output of a closed subsystem with other output (e.g., graphics and/or audio output) of the open computing system.

Abstract: In preferred embodiments, a cryptographic device in which two key sets are stored: a normal key set (typically unique to the device) and a test key set (typically used by each of a relatively large number of devices). The device uses the normal key set in a normal operating mode and uses the test key set in at least one test mode which can be a built-in self test mode. Alternatively, the device stores test data (e.g., an intermediate result of an authentication exchange) in addition to or instead of the test key set. In other embodiments, the invention is a cryptographic device including a cache memory which caches a portion of a key set for performing an authentication exchange and/or at least one authentication value generated during an authentication exchange. Other embodiments of the invention are systems including devices that embody the invention and methods that can be performed by systems or devices that embody the invention.

Abstract: In a class of embodiments, the invention is an open computing system (e.g., a PC) in which a protected, closed subsystem is embedded. The closed subsystem typically includes multiple parts that ensure that content protection keys and protected content are never revealed outside the closed subsystem. Content (e.g., high-definition digital video) that enters the closed subsystem (and is typically decrypted and re-encrypted within the closed subsystem) is afforded a similar level of protection within the open system as can be obtained in standalone closed systems. Other aspects of the invention are methods for protecting content within an open computing system, a closed system (or disk drive thereof) configured to be embedded in an open computing system, and circuitry configured to be embedded in an open computing system for combining the output of a closed subsystem with other output (e.g., graphics and/or audio output) of the open computing system.

Abstract: A communication system including a transmitter, a receiver, and a TMDS-like link, in which video data and auxiliary data are transmitted from the transmitter to the receiver, or in which video data are transmitted over the link from the transmitter to the receiver and auxiliary data are transmitted from the receiver to the transmitter (or from the transmitter to the receiver and also from receiver to the transmitter), a transmitter or receiver for use in such a system, and methods for sending auxiliary data and video data over such a link, synchronizing such auxiliary data with such video data, and generating clocks having frequency closely matching the rate at which the auxiliary data are transmitted. Typically, the auxiliary data include one or more streams of audio data.

Abstract: A communication system including a transmitter, a receiver, a communication link (for example, a TMDS-like link), and preferably also an external agent with which the transmitter and receiver can communicate, in which video data (or other data) are encrypted, the encrypted data are transmitted from the transmitter to the receiver, and the transmitted data are decrypted in the receiver, a transmitter and a receiver for use in such a system, a cipher engine for use in such a transmitter or receiver, a method for operating such a transmitter or receiver to encrypt or decrypt data, and a method for distributing keys to the transmitter and receiver. The receiver can be a player coupled to a downstream receiver by a TMDS-like link, and configured to re-encrypt the decrypted data (for example, using an AES or HDCP protocol) and send re-encrypted data over the link to the receiver.

Abstract: A method for adaptively filtering a control signal in a serial link includes monitoring for a blanking interval in a video stream having an associated clock signal and monitoring for an occurrence of a VSYNC signal once the blanking interval has started. A control signal is initially detected wherein the control signal occurs subsequent to the occurrence of the VSYNC signal. A set of properties of the control signal are recorded and a set of filter parameters are adjusted for detecting the control signal in a next blanking period based on the set of properties of the control signal.

Abstract: A communication system including a transmitter, a receiver, and a serial link (for example, a TMDS-like link) in which video data (or other data) are encrypted, the encrypted data are transmitted from the transmitter to the receiver, and the transmitted data are decrypted in the receiver, a transmitter and a receiver for use in such systems, a cipher engine for use in such a transmitter or receiver, a method for operating such a transmitter or receiver to encrypt or decrypt data, and a method for authenticating a receiver prior to transmission of encrypted data to the receiver over a serial link. Each transmitter, receiver, and cipher engine is configured to implement a content protection protocol in a manner that implements at least one and preferably more than one of a class of attack prevention features disclosed herein.

Abstract: A communication system including a transmitter, a receiver, and a serial link, that is capable of transmitting packets of data (e.g., frames of video data) over the link. The transmitter and receiver are operable in any selected one of a transmission mode (in which the data are transmitted over the link from the transmitter to the receiver) and a mute mode in which transmission of data over the link has been interrupted. Typically in the transmission mode, encrypted video data are transmitted and decrypted by the receiver. Other aspects of the invention are transmitters and receivers for use in, and methods implemented by, any embodiment of such system. Typically, each transition between transmission mode and mute mode operation requires that the device undergoing the transition (whether a transmitter or receiver) receives a warning that the transition is to occur.

Abstract: A communication system including a transmitter, a receiver, and a serial link, in which encoded data (e.g., video, audio, and optionally also other auxiliary data) are transmitted from the transmitter to the receiver. The serial link can but need not be a TMDS or TMDS-like link. In typical embodiments, packets of encoded audio data are transmitted over each of one or more channels of the link during data islands between bursts of encoded video data. Other aspects of the invention are transmitters for use in encoding data for transmission over a serial link, receivers for receiving such data, and methods for sending encoded data over a serial link.

Abstract: Read errors in data transferred from a remote memory to a buffer memory are detected and corrected by a series of error detection and correction techniques. In the present invention, the transferred data includes user data, a checksum that detects read errors in the user data, row and column syndromes that identifies read errors in the user data, and a Hamming code that identifies read errors in the row and column syndromes. To minimize any performance degradation, a checksum is initially calculated from the user data and compared with the stored checksum. If an error is detected, a Hamming code is calculated from the stored row and column syndromes and compared with the stored Hamming code. Corrections are made, as needed, and then row and column syndromes are calculated from the user data. The calculated row and column syndromes are then compared with the stored row and column syndromes the identify and correct single-bit read errors, and report multiple-bit read errors.