1. A method of biometric authentication of a test user, comprising the steps of: encrypting and storing, in a first device, a first data set derived from a biometric attribute of a reference user, wherein the biometric attribute is a voice print of a user and the first data set comprises multiple weight sets, each weight set corresponding to a respective neural network, each weight set and each neural network corresponding to a different voiced element; providing, in a second device separable from the first device, a plurality of untrained artificial neural networks prior to a time of authentication; obtaining at the time of authentication of the test user, by the second device, a second data set representative of the biometric attribute of the test user, wherein the second data set comprises components of speech input from the test user, the speech input comprising a plurality of voiced elements; transferring, over a wired or wireless data connection, the first data set from the first device to the second device at the time of authentication; decrypting and using the first data set as weights for the untrained neural networks in the second device to generate trained neural networks at the time of authentication; providing the second data set as inputs to the trained neural networks using input corresponding to each voiced element as an input to a respective one of said trained neural networks; and determining, from an average of the trained neural networks outputs corresponding to said inputs, a degree of correlation between the biometric attribute of the reference user and the biometric attribute of the test user.