Cryptography and biometrics have been identified as two of the most important aspects
of digital security environment. For various types of security problems the merging
between cryptography and biometrics has led to the development of Bio crypt technology.
The new technology suffers from several limitations and this thesis, addresses the
biometric information quality and the security weakness of cryptography. In many
applications fingerprint has been chosen as a core of bio crypt combined technology due
to it’s maturity in terms of availability, uniqueness, permanence, feasibility, ease of use
and acceptance. Fingerprint has been studied from the point of view of information
strength to suitability to the cryptographic requirement. The factors relating to generating
and constructing combined bio crypt key such as biometric image validity, quality
assessment and distinct feature extraction are studied to avoid corruptness of the source
biometric images. A number of contributions are made in this work, firstly, the analysis
of the validity and quality robustness of fingerprint images is undertaken, and a novel
algorithm is realised for circumventing these limitations. Secondly, new algorithms for
increasing the management security of image based biometric keys is described, via
shielding bio crypto information as another line of defence against serious attack. Finally,
fingerprint feature vector is proposed to replace minutiae based fuzzy vault to output high
entropy keys. This allows the concealment of the original biometric data such that it is
impossible to recover the biometric data even when the stored information in the system
is open to an attacker.