PhD defence, Thomas Thébaud

Date : 21/10/2022
Time : 9h45
Location : IC2, Le Mans University

Title : Spoofing attacks using behavioural biometric data reconstruction and statistical alignments

Jury members :

  • Najim DEHAK, Associate Professor, Johns Hopkins Whiting School of Engineering, Reviewer
  • Sébastien MARCEL, Professeur, IDIAP, Reviewer
  • Ruben VERA-RODRIGUEZ, Associate Professor, Universidad de Madrid, Examiner
  • Estelle CHERRIER, Maître de Conférence, ENSICAEN, Examiner
  • Jean-François BONASTRE, Professeur, LIA, Examiner
  • Grigory ANTIPOV, machine learning Engineer, Ubisoft, Examiner
  • Anthony LARCHER, Professeur, LIUM, Université du Mans, PhD Director
  • Gaël LE LAN, Chercheur, META FASTAI, Co-supervisor
  • Simon BECOT, Orange Business Services, Invited



Privacy protection is an ethical and legal duty in Europe. Biometric authentication systems are naturally implicated, as they use embeddings, extracted from biometric data. From a view between industry and academic, this thesis explore the embeddings vulnerabilities for data thieft and spoofing, applied to two behavioural biometries : Voice and handwritten digits. Template reconstruction attacks usually have an access to the encoder that produce the embeddings.

We proposed to use an unsupervised statistical alignment to analyze a set of embeddings without access to their encoder, to find their associated digits. By fine-tuning this alignment and using the adapted decoder, we reconstructed the digit drawings to spoof a digit authentication system. Speech reconstruction is more complex, because it contains linguistic information weakly transmetted through the embeddings, so we had to use a voice conversion system to reconstruct voice extracts well enough to spoof a speaker authentication system. We also proposed an inversion attack on a pseudo-anonymisation system, using supervised and unsupervised alignements on the raw and anonymized embeddings, to explore its limits.



Speaker Verification, Scriptor Verification, behavioural biometric authentication system spoofing, supervised and non supervised alignments, Reconstruction