Abstract: A method of frame synchronization for OFDM point-to-multipoint channels is provided according to a first aspect of the invention, wherein sequences of reference frames are inserted at prescribed intervals between sequences of information frames. Each frame comprises a cyclic prefix, composed of two identical segments of data, which is used for locating a frame synchronization starting point by applying a subtraction function on the two segments of data for locating the starting point at the location of the minimum of the function. A method of channel equalization for OFDM channels is also provided according to a second aspect of the invention, wherein the reference frames and data known to a receiver are used for creating an equalization vector for correcting broadcast errors of the information frames received at the receiver side.

Abstract: Apparatus and method for detecting surface defects on an article freely standing on a conveyer, which generate profile trace data corresponding to profile trace at a cross-section of the article. A surface shape inspection unit comprising an optical ranging system using laser and camera is provided for obtaining the profile trace data through triangulation-based derivation techniques. Base reference curves are derived from regular portions of the profile trace data. Profile trace data are compared to defect threshold curves to recognize a defect induced departure of the trace data with respect to the base reference curve and to produce a defect output signal. The apparatus and method according to the invention are particularly useful for detecting roughness, cavities, wane, missing wood and altered wood on lumber pieces which are conveyed at high speed.

Abstract: A new structure for a secret key cryptography algorithm uses double exclusive-or (XOR) encryption (e.sub.i =k1.sub.i XOR m.sub.i XOR k2.sub.1), analogue to a stream cipher arrangement, but providing data integrity protection. The double XOR encryption creates an inner sequence, for example s.sub.i =k1.sub.i XOR m.sub.i for the encryption process, s.sub.i =k2.sub.i XOR e.sub.i for the decryption process, which is unknown to the adversary and is used as a starting point for feedback on the very key streams used in the encryption of following bits of the message. In its preferred embodiment, this structure is the Frogbit data integrity algorithm which uses 10 independent pseudo-random sources. The Frogbit algorithm is well suited to the design and implementation of "semi-proprietary" ciphers, where the overall design is publicly known and peer-reviewed but a significant amount of the implementation specification is left open to private customization.

Abstract: An issuer offers any type of service secured with a secret cryptographic key assigned to an applicant according to the present invention, which includes a secret key registration process. Usually, the secret key will be loaded on a portable memory device or other secret key store of the applicant. As preliminary steps, the issuer sets up its public key for the Probabilistic Encryption Key Exchange (PEKE) cryptosystem, and the applicant obtains a copy of a secret key registration software, a copy of the issuer's public key, and an uninitialized portable memory device. Once initiated by the applicant, the registration software generates an internal PEKE secret key. The applicant chooses a registration pass query and pass reply that the registration software MACs and encrypts with a key derived from the PEKE secret key. The registration software derives the key assigned to the applicant from the PEKE secret key, and loads it into the secret key store.

Abstract: An electronic freezer thermometer alarm computes an estimation of contents temperature in a freezer from the freezer air temperature. The calculated contents temperature is displayed by a LCD display and is used to trigger a sound alarm, by use of a piezoelectric buzzer, in case of too high a value. Alternatively, the freezer air temperature is used to start a timer that triggers the alarm several minutes after the freezer air temperature have risen above the limit value. In this case, the displayed temperature is the freezer air temperature. In both cases, freezer air temperature acquisition is done by the resistance measurement of a thermoresistor placed into a small case constituting the temperature probe. The thermometer housing has two magnets to keep on freezer external surface. The temperature probe is connected to the housing by a small thickness of wire going under the freezer door gasket. The thermometer is energized by a lithium battery placed into the case.

Abstract: The present invention is directed to an optical system for measurement of a three dimensional device. The optical system is designed and configured to meet telecentric and f-.theta. requirements. The system employs primary and secondary mirrors operating in conjunction with a tertiary deflector mounted on a pivot. Light from a light source produces a beam which is deflected off the deflector and the secondary and primary reflectors respectively. The beam is then transmitted to the surface of the object to be measured. Deflection of the tertiary deflector on the pivot results in scanning of the light beam across the surface of the object to be measured.

Abstract: Calibration of a variable frequency light source is performed by a control unit which has a knowledge of the known transmission pattern of an optical filter, such as gas cell or a calibrated interferometer, having a number of known frequency dependent transmission characteristics in the tuning range of the optical source. This unit scans the frequency of the optical source via a frequency control signal over a frequency range and measures the optical intensity of the optical source output light after it has passed through the optical filter The measured transmission and frequency control signal values are processed and stored in memory and constitute a measured absorption pattern. Once acquired for a frequency range, this pattern is compared to the theoretical transmission pattern of the optical filter. Correspondences are made to identify the transmission features against their known counterparts. A relationship between the frequency control signal and actual frequency of the optical source is established.