Multi-core fiber (MCF) is one of the promising space-division multiplexing technologies to increase the capacity of optical networks. MCF-based networks have two challenges. One is the inter-core crosstalk (XT) that degrades the quality of optical signals in two neighboring fiber cores. The other is network protection against link failures that cause massive data loss. One way to protect against multiple link failures is to prepare physically separated links as a backup network. Probabilistic protection improves the efficiency of protection by allowing a certain probability of protection failure. Existing studies on backup network design with probabilistic protection do not target MCF-based networks, which raises problems such as protection failure due to the inter-core XT and excessive consumption of optical resources. To address these problems, this paper proposes a XT-aware backup network design model for the MCF optical path networks. The proposed model protects the network against probabilistic multiple link failures. We adopt probabilistic protection that allows a certain probability of protection failure due to the inter-core XT and minimizes the required number of links in the backup network. We present an algorithm to satisfy the probabilistic protection requirement and formulate the model as an integer linear programming problem. We develop a heuristic approach to apply the proposed model to larger networks. Numerical results observe that the proposed model requires fewer links than the dedicated allocation model, which provisions the backup paths in the same manner as the primary paths.

Logic encryption is an IC protection technique which inserts extra logic and key inputs to hide a circuit's functionality. An encrypted circuit needs to be activated with a secret key for being functional. SAT attack and Removal attack are two most advanced decryption methods that have shown their effectiveness to break most of the existing logic encryption methods within a few hours. In this paper, we propose SMARTLock, a SAT attack and reMoval Attack-Resistant Tree-based logic Locking method, for resisting them simultaneously. To encrypt a circuit, the method finds large AND and OR functions in it and encrypts them by inserting duplicate tree functions. There are two types of structurally identical tree encryptions that aim to resist SAT attack and Removal attack, respectively. The experimental results show that the proposed method is effective for encrypting a set of benchmarks from ISCAS'85, MCNC, and IWLS. 16 out of 40 benchmarks encrypted by the proposed method with the area overhead of no more than 5% are uncrackable by SAT attack within 5 hours. Additionally, compared to the state-of-the-art logic encryption methods, the proposed method provides better security for most benchmarks.