Abstract: There is decribed an apparatus for generating a number from data originating from an analogue source, the apparatus comprising means for performing a set of the data and then processing, in accordance with stored processing instructions predetermined by a training process, the data to generate the number. During the training process, the sensitivity of the value of the generated number to variation in each of the measurement values is analyzed, and the process instructions are generated so that the processing of individual measurement values is modified to reduce this sensitivity. In this way, the repeatability of the generated number is improved.

Abstract: There is described an authentication system in which during an enrolment process a distinctive characteristic of a subject being enrolled is measured to generate a reference number representative of the subject. Authentication data is then generated using the reference number, and the authentication data is stored for use in a subsequent verification process. During verification, the representative characteristic of the subject being verified is re-measured to generate a test number representative of the subject being verified and the authentication data during enrolment is retrieved. The authentication system then checks for equality between the test number and the reference number using the retrieved authentication data. If the test number and the reference number are equal, then the authenticity of the subject is verified, otherwise the authenticity is denied.