The concept of blockchain, widely known as virtual currencies, saw a massive surge in popularity in recent times. As far as the security of the blockchain is concerned, consensus algorithms play a vital role in the blockchain. Research has been done separately, or comparisons between a few of them have been presented previously. In this paper, we have discussed widely used consensus algorithms in the blockchain. The consensus protocols covered in this paper include PoW (Proof of Work), PoS (Proof of Stake), DPoS (Delegated Proof of Stake), PoET (Proof of Elapsed Time), PBFT (Practical Byzantine Fault Tolerance), and PoA (Proof of Authority). For each consensus, we have reviewed the properties, applications, and performance in the blockchain.
This paper describes a new deniable authentication protocol whose security is based Diffe-Hellman (CDH) Problem of type Decisional Diffie-Hellman(DDH) and the Hash Diffie-Hellman (HDDH) problem. Here we have used pairing technique i.e the problem is called Bilinear Diffie Hellman (BDHP) problem. The protocol is of identity-based and can be implemented in low power and small processor mobile devices such as smart card, PDA etc. A deniable authentication protocol enables a receiver to identify the true source of a given message, but not to prove the identity of the sender to a third party. This property is very useful for providing secure negotiation over the internet. Our proposed protocol will be achieving the most three security requirement like deniable authentication, authentication and confidentialities. Also it is resistant against Man-in middle Attack.
As security is essential in communications through electronic networks, development of structures providing high levels of security is needed. Public Key Infrastructure (PKI) is a way of providing security measures by implementing the means of key pairs among users. In this paper, an overview of the public key infrastructure is discussed that includes various components and operation, some well known PKIs and their comparisons. Also we discuss current implementations, risk and challenges of PKIs.
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