Patent ID: 8583936

Claim:
A method of generating encryption keys for encrypting communications between terminals including a first terminal and a second terminal, the acts of: obtaining a measurement of characteristics of a physical identifier of a user; extracting a first key from the physical identifier using a first code selected from a collection of codes, each code in the collection defining an ordered mapping from regions including a set of values of the characteristics to a set of keys; wherein the collection of codes comprises at least one code in which the ordered mapping is a permutation of the ordered mapping of one of the other codes in the collection for mapping from a particular set of values of characteristics of the physical identifier to a particular key; generating a first encryption key from the first key for encrypting the communications between the first terminal and the second terminal; extending the collection of codes by adding permuted versions of the codes including the permutation of the ordered mapping of one of the other codes; extracting a second key from the physical identifier using a second code, wherein the second code is one of the permuted versions of the codes; and generating a second encryption key from the second key for encrypting the communications between the first terminal and a further terminal, and wherein a number of available permutations is equal to a number of the regions and a number of the keys.