Cryptographic Protocols Provably Secure Against Dynamic Adversaries

Ronald Cramer

Bartosz Przydatek

Zvi Galil, Jonathan I. Katz

In the analysis of many cryptographie protocole, it is useful to distinguish two classes of attacks: passive attacks in which an adversary eavesdrops on messages sent between honest users and active attacks (i.e, “man-in-the-middle” attacks) in which—in addition to eavesdropping—the adversary inserts, deletes, or arbitrarily modifies messages sent from one user to another. Passive attacks are well characterized (the adversary's choices are inherently limited) and techniques for achieving security against passive attacks are relatively well understood. Indeed, cryptographers have long focused on methods for countering passive eavesdropping attacks, and much work in the 1970's and 1980's has dealt with formalizing notions of security and providing provably-secure solutions for this setting. On the other hand, active attacks are not well characterized and precise modeling has been difficult. Few techniques exist for dealing with active attacks, and designing practical protocols secure against such attacks remains a challenge. This dissertation considers active attacks in a variety of settings and provides new, provably-secure protocols preventing such attacks. Proofs of security are in the standard cryptographie model and rely on well-known cryptographie assumptions. The protocols presented here are efficient and practical, and may find application in real-world systems.

Vipul Goyal

Brij Bhooshan Gupta, Aakanksha Tewari

Internet of Things (IoT) devices have restricted resources and energy; however, they require regular updates and identification from other devices and the backend server. Thus, security is also a major concern, and the most common way to do it is mutual authentication between the communicating parties. Provable security aims to provide concrete mathematical proof for ensuring the protocol’s security. Modern cryptographic protocols deploy “game-based” security models, which have an adversary that can carry out potential attacks over the concerned system. The adversary in the universally composable security model interacts with both real-world and ideal-world environments. The adversary can eavesdrop into all the communications and can schedule the activation sequence of the entities. The real spreading of IoT services requires customized security and privacy levels to be guaranteed. K. Ouafi et al. have extended Vaudeney’s model to incorporate the notion of strong privacy.

Vipul Goyal