Attacks and Improvement of Unlinkability of Biometric Template Protection Scheme Based on Bloom Filters

Biometric technologies are being prominently used everywhere. However, the leakage of biometric information can pose a serious security risk, making the protection of biometric templates particularly important and receiving more attention. Rathgeb et al. first proposed the cancelable biometric technology based on Bloom filters in 2013. Bloom filter-based biometrics offer the advantages of alignment-free, fast recognition and high accuracy. An ideal biometric system should also be irreversibility and unlinkability. In this paper, firstly, we propose a reverse reconstruction attack. The biometric data reconstructed from Bloom filters have some strong statistical correlation with the original biometric data, which proves that the original scheme has the linkability defect. Experiments show that for the original Bloom filter-based biometric template protection scheme, we can judge whether two different biometric templates belong to the same user with a success probability of 71.0%. Secondly, to remedy above defect, we construct a structure-preserving encryption scheme, i.e., the encrypted feature template maintains the structure and length of the original template, making it impossible for an attacker to reconstruct meaningful data from Bloom filter. Finally, an improved biometric template protection scheme based on Bloom filters is proposed by introducing the proposed encryption. Attack experiment shows that the improved scheme can effectively resist the reverse reconstruction attack, the success probability of discrimination is reduced to 50%, which is the same as the probability of random guessing. Performance evaluation shows that the proposed scheme maintains the biometric performance of the original system and the unprotected system.