Internet of Things (IoT)- based services connect the user with sensing devices through intermediary devices like a gateway. The authentication with secure key exchange assures security trio of confidentiality, integrity, and availability for the complete IoT-based system. It also ensures trusted privacy of communicated information. Recently, numerous authors proposed a Remote User Authentication scheme (RUA) on User-Gateway based secure key exchange for the tiny and lightweight sensor based paradigms such as an IoT and a wireless sensor network (WSN) using lightweight mathematical approaches. In this article, we propose a reliable and efficient lightweight key exchange scheme with the secure RUA for the user-gateway model. For designing a lightweight RUA scheme, we use elliptic curve cryptography (ECC). We use BAN-Logic for the validation of mutual authentication. We use widely accepted random oracle-based ROR model for formal security analysis and Dolev-Yao channel for informal security analysis. For the implementation and result collection of the proposed scheme, we used publisher-subscriber-based lightweight Message Queuing Telemetry Transport (MQTT) protocol. Overall, in this article, we propose a highly secure and efficient RUA scheme for the sensor-based environment with the formal security analysis and real-time implementation.

Abstract In CRYPTO'13, Gentry et al. proposed the first homomorphic encryption (HE) scheme for the attribute‐based encryption (ABE). However, Gentry's scheme requires the same index for encryption of each ciphertext and supports only the key‐policy ABE. Indeed, in SECRYPT'13, Clear et al. left an open problem in the Gentry et al. scheme viz. a scheme that requires different sets of index in HE using ABE and supports the ciphertext‐policy ABE (CP‐ABE), where the sender is assumed to be intelligent. In addition, in INDOCRYPT'12, Vaikuntanathan discussed an open problem viz. to work out the HE using cryptographic techniques other than lattice‐based cryptography. With an aim to propose the CP‐ABE scheme using HE, in this research attempt, we propose an approach that integrates the benefits of HE in CP‐ABE and yet uses pairing‐based cryptography. In our approach viz. attribute‐based HE (AB‐HE), a user is able to successfully decrypt the ciphertext only if the attributes in the policy match those in the secret key. However, in addition, our approach also allows multiple invocations of multiplication operation on the ciphertext as in a typical partially HE, coupling the advantages of the partial HE in the CP‐ABE. Further, we also propose an extension of the proposed scheme that serves as a pseudo‐fully HE, but requires the help of a key authority. The security of the proposed scheme is based on the decisional bilinear Diffie–Hellman problem. To the best of our knowledge, ours is a unique attempt in integrating HE into the attribute‐based cryptography with different indexes/policies. In addition, our AB‐HE scheme is pairing‐based, and by adding more ciphertexts, it does not blow the final ciphertext size because we use the constant length ciphertext approach for the encryption. Copyright © 2016 John Wiley & Sons, Ltd.

ABSTRACT In PKC 2010, Herranz et al. proposed the first fully threshold ciphertext policy attribute‐based encryption (CP‐ABE) scheme with constant length ciphertext. However, their scheme is selectively secure with respect to the chosen plaintext attack. They have left three open problems for CP‐ABE with constant ciphertext length, that is, Security against the Chosen Ciphertext Attacks, Security Reduction to a better mathematical problem and to make the scheme Fully Secure. Indeed, in ACISP 2012, Ge et al. proposed the solutions to the first two problems but left their proposed scheme selective secure. This makes their scheme weaker because it is secure only for a particular policy. With an aim to propose a fully secure constant ciphertext length CP‐ABE scheme, in this paper, we discuss our attempts at extending the approach of Lewko et al. (in EUROCRYPT 2010). The scheme that we propose here allows any subset of attributes of the secret key as a part of the ciphertext policy. Copyright © 2013 John Wiley & Sons, Ltd.