Abstract: This invention describes a secure method for consistently reproducing a digital key using a biometric, such as a fingerprint. The digital key is linked to the biometric only through a secure block of data, known as the protected filter. The key cannot be released from the protected filter other than via the interaction with the correct biometric image. Once generated, the digital key may be used in a system as an encryption/decryption key, or as a personal identification number (PIN).

Abstract: A hybrid optical-digital technique is provided for automatic fingerprint verification. A coherent optical beam modulated with the characteristics of a fingerprint image passes through the lens performing an optical Fourier transform. The intensity array that represents the Fourier power spectrum is recorded and processed. In enrolment, several arrays related to the same finger are captured and processed. A template which is unique for each fingerprint is generated and stored. Using the set of arrays captured in enrolment and a set of templates from a standard database, the processor calculates dependences of false rejection rate and false acceptance rate upon a metric of comparison. The metric is obtained by calculating a relative distance between two arrays in Hilbert space. An individual threshold of verification for a person to be enroled is set and stored together with the template.

Abstract: A key generation system is implemented as follows. In an enrolment apparatus, a unique number for use with PIN operated machines or public key cryptography systems is generated by manipulation of fingerprint information of a subscriber. A filter is then generated which is a function both of the Fourier transform of the subscriber's fingerprint(s) and of the unique number. This filter is stored on a subscriber card. When the subscriber wishes to generate his key, he inputs his card to a card reader of an apparatus and places his finger(s) on a fingerprint input. The apparatus generates an optical Fourier transform from the fingerprint input. The Fourier transform signal is incident on to a spatial light modulator programmed with the filter information from the card. An inverse transform is generated from the filtered signal and this is used to regenerate the key that will be used as the PIN in a PIN operated device, or as the private key cryptography system.