Chiara-Marie Zok successfully defended her Master’s thesis on Efficient Multibiometric Two-Factor Authentication Using Homomorphic Transciphering

Biometric authentication is used in day-to-day life and in highly sensitive situations such as border control. Therefore, biometric features are extracted from samples and stored in biometric templates. Previous work has proven that samples can be reconstructed from templates. Therefore, template protection using Fully Homomorphic Encryption (FHE) has been shown to be effective in preventing such attacks. However, FHE is too resource intensive in systems where one participant has significantly low computational power. A further security risk is the low entropy for single biometric features. Homomorphic transciphering in combination with multibiometrics has the potential to solve both problems at the same time. Homomorphic transciphering is the process of transforming a symmetric ciphertext in a homomorphically encrypted ciphertext. In this thesis, two-factor authentication is achieved through transciphering. It is shown how multiple features of varying lengths and data types can be compared in the encrypted domain.