Cifração e autenticação utilizando funções fisicamente não clonáveis (PUFs)

This work presents applications based on a recent primitive called Physically Unclonable Functions (PUFs), and how they can be used to establish security properties. In this work, PUFs are employed to construct a block cipher and authenticator, where the rst is constructed from a Luby-Racko cipher with 4 rounds involving PUFs and universal hash functions. The cipher improves the state of the art of PUF-based encryption in two aspects: security and size of the resulting ciphertext. The second, a Message Authentication Code (MAC) is built by the combination of a classic xed-size MAC with a universal hash function. In both cases, security analysis are provided considering standard notions in the literature. Since the PUFs implicitly encode cryptographic keys, the techniques presented can be used in authenticated encryption schemes of hard drives or mobile devices, increasing resistance against leakage of key bits. Besides the proposed construction of a cipher and an authenticator, we propose an authentication protocol for banking applications combining PUFs with protocols for Password-based Authenticated Key Exchange (PAKE). The resulting protocol provides mutual authentication between client and server and establishes a session key between the authenticated parties, important features that were not found simultaneously in the literature of PUF-based authentication. This combination improves the state of the art, ensuring that the session key is only available to legitimate holders of the PUF, reducing the possibility of leaking secrets stored explicitly. The protocol supports multiple authentication factors and provides protection against o ine dictionary attacks on the password authentication. Moreover, it satis es the usual security notions when the PUF output is unpredictable, and allows the client to notify the server in case of emergency.