A symmetric group key agreement protocol enables the group members to derive a shared session key for secure communication among them, while an asymmetric one facilitates security to any communication from outside, without adding outsiders into the group. In this paper, we propose a twofold group key agreement protocol which addresses the need of a shared symmetric key among insider members in a group and an asymmetric key pair for any unrestricted sender. In particular, we look forward for a solution to provide secure communication among multiple processing clusters (PCs) actively running on an integrated circuit (IC). The proposed protocol offers a lightweight symmetric encryption for intra zone communication and a public key encryption for inter zone communication taking most advanced security issues into account.

Public-key encryption with keyword search (PEKS) schemes are useful to delegate searching capabilities on encrypted data to a third party, who does not hold the entire secret key, but only an appropriate token which allows searching operations but preserves data privacy. We propose an efficient and practical integrated public-key encryption (PKE) and public-key encryption with keyword search (PEKS) scheme (PKE+PEKS) which we prove to be secure in the strongest security notion for PKE+PEKS schemes. In particular, we provide a unified security proof of its joint CCA-security in standard model. The security of our scheme relies on Symmetric eXternal Diffie-Hellman (SXDH) assumption which is a much simpler and more standard hardness assumption than the ones used in most of the comparable schemes. Ours is the first construction to use asymmetric pairings which enable an extremely fast implementation useful for practical applications. Finally we compare our scheme with other proposed integrated PKE+PEKS schemes and provide a relative analysis of its efficiency.

Proxy signature scheme enables a signer to delegate its signing rights to any other user, called the proxy signer, to produce a signature on its behalf. In a proxy multi-signature scheme, the proxy signer can produce one single signature on behalf of multiple original signers. We propose an efficient and provably secure threshold-anonymous identity-based proxy multi-signature (IBPMS) scheme which provides anonymity to the proxy signer while also providing a threshold mechanism to the original signers to expose the identity of the proxy signer in case of misuse. The proposed scheme is proved secure against adaptive chosen-message and adaptive chosen-ID attacks under the computational Diffie-Hellman assumption. We compare our scheme with the recently proposed anonymous proxy multi-signature scheme and other ID-based proxy multi-signature schemes, and show that our scheme requires significantly less operation time in the practical implementation and thus it is more efficient in computation than the existing schemes.