Applications of electron microscopy to the characterization of semiconductor nanowires

We review our current progress on semiconductor nanowires of β-Ga2O3, Si and GaN. These nanowires were grown using both vapor–solid (VS) and vapor–liquid–solid (VLS) mechanisms. Using transmission electron microscopy (TEM) we studied their morphological, compositional and structural characteristics. Here we survey the general morphologies, growth directions and a variety of defect structures found in our samples. We also outline a method to determine the nanowire growth direction using TEM, and present an overview of device fabrication and assembly methods developed using these nanowires

KDM Security for Identity-Based Encryption: Constructions and Separations

For encryption schemes, key dependent message (KDM) security requires that ciphertexts preserve secrecy even when the messages to be encrypted depend on the secret keys. While KDM security has been extensively studied for public-key encryption (PKE), it receives much less attention in the setting of identity-based encryption (IBE). In this work, we focus on the KDM security for IBE. Our results are threefold. We first propose a generic approach to transfer the KDM security results (both positive and negative) from PKE to IBE. At the heart of our approach is a neat structure-mirroring PKE-to-IBE transformation based on indistinguishability obfuscation and puncturable PRFs, which establishes a connection between PKE and IBE in general. However, the obtained results are restricted to selective-identity sense. We then concentrate on results in adaptive-identity sense. On the positive side, we present two constructions that achieve KDM security in the adaptive-identity sense for the first time. One is built from identity-based hash proof system (IB-HPS) with homomorphic property, which indicates that the IBE schemes of Gentry (Eurocrypt 2006), Coron (DCC 2009), Chow et al. (CCS 2010) are actually KDM-secure in the single-key setting. The other is built from indistinguishability obfuscation and a new notion named puncturable unique signature, which is bounded KDM-secure in the single-key setting. On the negative side, we separate CPA/CCA security from $n$-circular security (which is a prototypical case of KDM security) for IBE by giving a counterexample based on differing-inputs obfuscation and a new notion named puncturable IBE. We further propose a general framework for generating $n$-circular security counterexamples in identity-based setting, which might be of independent interest

On the RCCA Security of Hybrid Signcryption for Internet of Things

With the rapid development of the Internet of Things (IoT), a lot of sensitive information in our daily lives are now digitalized and open to remote access. The provision of security and privacy of such data would incur comprehensive cryptographic services and has raised wide concern. Hybrid signcryption schemes could achieve various kinds of cryptographic services (e.g., confidentiality, authenticity, and integrity) with much lower cost than the combination of separate traditional cryptographic schemes with each providing a single cryptographic service. Thus, hybrid signcryption schemes are very suitable for IoT environments where resources are generally very constrained (e.g., lightweight sensors and mobile phones). To ensure that the overall hybrid signcryption scheme provides adequate cryptographic service (e.g., confidentiality, integrity, and authentication), its parts of KEM (key encryption mechanism) and DEM (data encryption mechanism) must satisfy some security requirements. Chosen-ciphertext attack (CCA) security has been widely accepted as the golden standard requirement for general encryption schemes. However, CCA security appears too strong in some conditions. Accordingly, Canetti et al. (CRYPTO 2003) proposed the notion of replayable CCA security (RCCA) for encryption schemes, which is a strictly weaker security notion than CCA security and naturally more efficient. This new security notion has proved to be sufficient for most existing applications of CCA security, e.g., encrypted password authentication. This is particularly promising for IoT environments, where security is demanding, yet resources are constrained. In this paper, we examine the RCCA security of the well-known SKEM+DEM style hybrid signcryption scheme by Dent at ISC 2005. Meanwhile, we also examine the RCCA security of the Tag-SKEM+DEM style hybrid signcryption scheme by Bjorstad and Dent at PKC 2006. We rigorously prove that a hybrid signcryption scheme can achieve RCCA security if both its SKEM part and its DEM part satisfy some security assumptions