A device for using biometric data to authenticate a subject as an individual whose biometric data has been previously obtained using a first transducer, without the need for non-transient storage of the biometric data, the device comprising: a second transducer; and a computing facility that is coupled to the second transducer, the computing facility including a computing processor and a non-transitory computer readable storage medium encoded with instructions that, when executed by the computing processor, establish computer processes comprising: receiving by the computing facility, from the second transducer, a digital electronic signal that characterizes a biometric of the subject; extracting by the computing facility, from the digital electronic signal, (a) a set of biometric values of the subject and (b), for each member of the set of biometric values of the subject, a confidence value indicating a degree of confidence that the corresponding biometric value is stable between characterizations; encoding the set of biometric values of the subject to have a marker at locations where features are present, and where features are not present, to have noisy data; using the confidence values to select, by the computing facility, a confident subset of the encoded set of biometric values of the subject, the confident subset being a reliable discriminant of the identity of the subject based on the biometric; receiving, by the computing facility, from a storage facility, (i) a hash F of a secret number S and (ii) a biometric public key B that was computed based on the secret number S and the biometric data of the individual that has been previously obtained using the first transducer, wherein the biometric data of the individual had been encoded to have a marker at locations where features are present and, where features are not present, to have noisy data; computing, by the computing facility, a candidate value S' for the secret number S using the biometric public key and the confident subset; and performing an authentication process by determining whether the candidate value S' is deemed equivalent to the secret number S. a second transducer; and a computing facility that is coupled to the second transducer, the computing facility including a computing processor and a non-transitory computer readable storage medium encoded with instructions that, when executed by the computing processor, establish computer processes comprising: receiving by the computing facility, from the second transducer, a digital electronic signal that characterizes a biometric of the subject; extracting by the computing facility, from the digital electronic signal, (a) a set of biometric values of the subject and (b), for each member of the set of biometric values of the subject, a confidence value indicating a degree of confidence that the corresponding biometric value is stable between characterizations; encoding the set of biometric values of the subject to have a marker at locations where features are present, and where features are not present, to have noisy data; using the confidence values to select, by the computing facility, a confident subset of the encoded set of biometric values of the subject, the confident subset being a reliable discriminant of the identity of the subject based on the biometric; receiving, by the computing facility, from a storage facility, (i) a hash F of a secret number S and (ii) a biometric public key B that was computed based on the secret number S and the biometric data of the individual that has been previously obtained using the first transducer, wherein the biometric data of the individual had been encoded to have a marker at locations where features are present and, where features are not present, to have noisy data; computing, by the computing facility, a candidate value S' for the secret number S using the biometric public key and the confident subset; and performing an authentication process by determining whether the candidate value S' is deemed equivalent to the secret number S. receiving by the computing facility, from the second transducer, a digital electronic signal that characterizes a biometric of the subject; extracting by the computing facility, from the digital electronic signal, (a) a set of biometric values of the subject and (b), for each member of the set of biometric values of the subject, a confidence value indicating a degree of confidence that the corresponding biometric value is stable between characterizations; encoding the set of biometric values of the subject to have a marker at locations where features are present, and where features are not present, to have noisy data; using the confidence values to select, by the computing facility, a confident subset of the encoded set of biometric values of the subject, the confident subset being a reliable discriminant of the identity of the subject based on the biometric; receiving, by the computing facility, from a storage facility, (i) a hash F of a secret number S and (ii) a biometric public key B that was computed based on the secret number S and the biometric data of the individual that has been previously obtained using the first transducer, wherein the biometric data of the individual had been encoded to have a marker at locations where features are present and, where features are not present, to have noisy data; computing, by the computing facility, a candidate value S' for the secret number S using the biometric public key and the confident subset; and performing an authentication process by determining whether the candidate value S' is deemed equivalent to the secret number S.