Abstract: A method and apparatus for authenticating (or identifying) a subject, includes using one or a plurality of biometric measurements for authentication (or identification) without any sharing of the subject's biometric data with a party requesting authentication.

Abstract: A watermarking method involves mostly invisible artifacts and is sensitive to any modification of the picture at the level of precision rendered by the compressed version of the image. The image is compressed according to a known compression standard, such as the JPEG standard, and with a fixed quality setting. Using the JPEG standard, the original image is cut into blocks to which the Discrete Cosine Transform (DCT) is applied and the DCT coefficients quantized. The watermark according to the invention is applied to the quantized DCT coefficients. This is done using an encryption function, such as a secret key/public key algorithm. The JPEG compression is then completed using a lossless compression scheme, such as Huffman coding, to produce the compressed and watermarked image. Authentication of the compressed and watermarked image begins with a lossless decompression scheme to obtain the set of quantized DCT coefficients. The coefficients are authenticated, and the DCT output of each block is dequantized.

Abstract: Code modification circuitry alters the end portion of each block in a sequence of code blocks, and also inserts additional bits at the junction between contiguous blocks. The codes to be processed are run-length limited (RLL) codes having a DC component which is to be removed for certain applications such as magnetic recording. The modification circuitry retains the RLL format. Charge (or the integral of the waveform) accumulated by the sequence of bits of one block is compensated by selecting the sense of charge accumulation in next block to be of opposite sense. This is accomplished by the code modification circuitry using a relatively small set of possible combinations of digital words at the junctions of the blocks.