This work describes certain special art of biometric systems. If we try to combine a biometric (fingerprint) system with some cryptographic system, we are confronted with the question, if there is enough information in the fingerprint. Some computations of the similarity among fingerprints have already been published but they have considered the matching of fingerprints. For cryptographic tasks, it is more important to exploit the information strength hidden in fingerprint papillary line structures. The answer to this question can be found in this work. If the information strength is adequate to the cryptographic requirements, we can design a system, which uses fingerprint technology as a biometric information input and offers biometric keys to the cryptographic subsystem. The detailed description of such biometric security system can be found also in this work, where all processes needed for the computations and processing are described.