Concordância de chave secreta aplicada a controle de acesso utilizando biometria da íris e sistemas RFID.

Abstract

This thesis deals with cryptographic keys based on biometrics. We propose a new technique named Biometrics-Based Secret Key Agreement by Public Discussion with RFID systems (BSKAPD-RFID). Three safety factors are used, represented by an iris code, an RFID tag and a password. An information reconciliation (IR) protocol that does not require the traditional advantage distillation and privacy amplification phases is proposed. The IR protocol performed by the RFID reader and tag enables a symmetric key agreement by discarding all the mismatching bits present in genuine samples, while it can not do it by impostors, who are therefore rejected. The BSKAPD system, besides adding revocability to generated keys, allows crypto-bio key agreement between devices through wireless communication. These agreed keys have high entropy, when compared with those obtained by others crypto-biometric systems, as crypto-bio key regeneration systems. Another important safety feature is the renewal of the symmetric key every positive authentication process. Analytic expressions for IR protocol were derived and validated. The system was evaluated on the public database ICE2005 and obtained a 270 binary digit cryptographic key with estimated entropy of about 156 bits at False Acceptance Rate (FAR) of 0.00 % and at False Rejection Rate (FRR) of 3.68 %. Finally, an improvement of the algorithm for the Daugman’s iris recognition method is introduced. It was designed for applications that have restrictions on the use of occlusion mask, as occurs in the BSKAPD system. The distribution of the application points, after application of the mentioned algorithm, is such that avoid regions with high rate of occlusions by eyelids and eyelashes, therefore, reducing the impact of not using the occlusion mask in the matching step.