Abstract: A method and apparatus for coding and decoding information are disclosed. The method is for encoding a message that includes a first set of binary digits. Each binary digit has a first value (“0”) or a second value (“1”). The method includes receiving a first set of binary digits, generating a second set of binary digits in response to the first set of binary digits (Y), and selecting the values of binary digits in the second set such that the number of binary digits having the first binary value in the second set is higher than the number of binary digits having the first binary value in the first set.

Abstract: Method and apparatus for providing secure, controlled access to one or more functions in an electronic system which may have a plurality of functions having different access requirements. A desired function is enabled according to the result of a first authentication process which uses a public key which corresponds to the desired function, and access to the function is authorized by a second authentication process which uses a second, private session key computed as a result of a random challenge made by the system to an external entity during the first authentication process. Additional protection is also provided against passive and active wiretapper attacks, such that only an entity that has received authorization can access the system at the correct access level.

Abstract: The invention relates to a method for encoding an analogue signal having an amplitude with a non-uniform probability density. The method includes quantising the signal as falling within one of plural signal level ranges, and coding the quantised signal by assigning codewords to the quantising levels so as to generate a binary coded message. Each codeword has plural binary-valued digits. The codewords are assigned to the quantising levels in accordance with the occurrence probability of the quantising levels and the number of bits having a first value in the codeword such that quantisation levels of higher occurrence probability are assigned codewords with fewer bits having a first value than those assigned to quantisation levels of lower occurrence probability. The coding includes generating the binary coded message such that the number of bits in the coded message is minimized.