Biblio

To protect against misuse of passwords compromised in a breach, consumers should promptly change affected passwords and any similar passwords on other accounts. Ideally, affected companies should strongly encourage this behavior and have mechanisms in place to mitigate harm. In order to make recommendations to companies about how to help their users perform these and other security-enhancing actions after breaches, we must first have some understanding of the current effectiveness of companies’ post-breach practices. To study the effectiveness of password-related breach notifications and practices enforced after a breach, we examine—based on real-world password data from 249 participants—whether and how constructively participants changed their passwords after a breach announcement. Of the 249 participants, 63 had accounts on breached domains; only 33% of the 63 changed their passwords and only 13% (of 63) did so within three months of the announcement. New passwords were on average 1.3× stronger than old passwords (when comparing log10-transformed strength), though most were weaker or of equal strength. Concerningly, new passwords were overall more similar to participants’ other passwords, and participants rarely changed passwords on other sites even when these were the same or similar to their password on the breached domain. Our results highlight the need for more rigorous passwordchanging requirements following a breach and more effective breach notifications that deliver comprehensive advice.

Many self-adaptive systems benefit from human involvement and oversight, where a human operator can provide expertise not available to the system and can detect problems that the system is unaware of. One way of achieving this is by placing the human operator on the loop – i.e., providing supervisory oversight and intervening in the case of questionable adaptation decisions. To make such interaction effective, explanation is sometimes helpful to allow the human to understand why the system is making certain decisions and calibrate confidence from the human perspective. However, explanations come with costs in terms of delayed actions and the possibility that a human may make a bad judgement. Hence, it is not always obvious whether explanations will improve overall utility and, if so, what kinds of explanation to provide to the operator. In this work, we define a formal framework for reasoning about explanations of adaptive system behaviors and the conditions under which they are warranted. Specifically, we characterize explanations in terms of explanation content, effect, and cost. We then present a dynamic adaptation approach that leverages a probabilistic reasoning technique to determine when the explanation should be used in order to improve overall system utility.

Zigbee network security relies on symmetric cryptography based on a pre-shared secret. In the current Zigbee protocol, the network coordinator creates a network key while establishing a network. The coordinator then shares the network key securely, encrypted under the pre-shared secret, with devices joining the network to ensure the security of future communications among devices through the network key. The pre-shared secret, therefore, needs to be installed in millions or more devices prior to deployment, and thus will be inevitably leaked, enabling attackers to compromise the confidentiality and integrity of the network. To improve the security of Zigbee networks, we propose a new certificate-less Zigbee joining protocol that leverages low-cost public-key primitives. The new protocol has two components. The first is to integrate Elliptic Curve Diffie-Hellman key exchange into the existing association request/response messages, and to use this key both for link-to-link communication and for encryption of the network key to enhance privacy of user devices. The second is to improve the security of the installation code, a new joining method introduced in Zigbee 3.0 for enhanced security, by using public key encryption. We analyze the security of our proposed protocol using the formal verification methods provided by ProVerif, and evaluate the efficiency and effectiveness of our solution with a prototype built with open source software and hardware stack. The new protocol does not introduce extra messages and the overhead is as lows as 3.8% on average for the join procedure.