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A Survey on Various Applications of Internet of Things on Blockchain Platform
Published in Debarka Mukhopadhyay, Siddhartha Bhattacharyya, Balachandran Krishnan, Sudipta Roy, Blockchain for IoT, 2023
Archana Yengkhom, Debarka Mukhopadhyay
Current popular databases are based on a client/server architecture, a centralized access control system. The client plays the role of receiving nodes, and the server maintains the central authority in a distributed system. This was shaped to meet the traditional human–machine interaction. Meanwhile, Blockchain is founded on a decentralized system, where each node in the network communicates on a P2P protocol. Blockchain technology, as the name suggests, is a sequence-chain of blocks that store transaction records, digitally and tamper-proof. This is achieved via the concept of a Merkle Tree or Hash Tree; it is a tree-based data structure that maintains data integrity and synchronization for a distributed network by exploiting the hash functions. A cryptography hash (digest) acts as a digital signature due to its uniqueness in terms of text or data. A hash function is a method that ensures the immutability of data as it maps a unique output for a specific input; the input cannot be derived from its output. This is further enhanced by using hexadecimal for maturing the SHA-256 bit (Secured Hash Algorithm) cryptography function. It produces a unique signature and plays a key role in the data integrity for BCT.
Reliable Data Auditing and ACO-Based Resource Scheduling for Cloud Services
Published in Indrajit Pan, Mohamed Abd Elaziz, Siddhartha Bhattacharyya, Swarm Intelligence for Cloud Computing, 2020
Merkle tree is a hash tree used for cryptographic purposes [3]. It follows the structure of complete binary tree [4]. Every leaf node of Merkle tree contains a data block. Subsequent parent node contains hash of that data contained within the data block. Cryptographic hash function [5] is used to hash these data blocks. A Merkle tree is shown in Figure 4.2. The four leaf nodes are representing four data blocks (D1, D2, D3 and D4). First, a cryptographic hash function is used to individually hash these data blocks. Penultimate ancestor blocks of the leaf nodes hold the hash of their respective child blocks (e.g. Hash (D1) is H1). Afterward, two adjacent hashed blocks are taken together from left to right direction, and they are hashed (e.g. parent blocks of H1 and H2 contain their hash H12). Finally, the root contains the final hash block of whole tree. The root with H1234 in Figure 4.2 contains Merkle hash of all data blocks.
Applications to Cryptography
Published in Suman Saha, Shailendra Shukla, Advanced Data Structures, 2019
Blocks in a block chain contain valid transactions that are encoded and hashed by Merkle trees. Merkle tree is also known as hash tree, where leaf node is labeled with hash of data block and non leaf nodes are labelled with cryptographic hash. Markel tree helps in efficient and secure verification of large data structure (as illustrated in Figure 12.2). Each block has the cryptographic hash value of the previous block in the block that unites the two. The connected blocks cascade to form a chain. This iterative process confirms the integrity of the previous block to the original generation block [162]. Sometimes, the blocks can be produced at the same time, creating a temporary bifurcation. Each block has a specific algorithm to evaluate different versions of the history, so a higher value can be chosen. Blocks not selected for inclusion in the chain are called “orphans”.
A novel blockchain-based privacy-preserving framework for online social networks
Published in Connection Science, 2021
Shiwen Zhang, Tingting Yao, Voundi Koe Arthur Sandor, Tien-Hsiung Weng, Wei Liang, Jinshu Su
In 2008, Satoshi Nakamoto first proposed the concept of blockchain, which served as the public transaction ledger of the Bitcoin cryptocurrency (Nakamoto, 2008). The transaction data is sequentially stored on the ledger in the order of their timestamp of generation. In the blockchain network, the data is maintained by all the nodes. Each node is autonomous and enables to obtention of a complete set of data. Thus it can tolerate the single point of failure. Blockchain consists of data layer, network layer, consensus layer, incentive layer, contract layer and application layer. A blockchain system is deployed in a peer to peer network, which collectively follows a pre-defined consensus protocol (Yang et al., 2018). The essence of blockchain is a disturbed and tamper resistant transactions database. The structure of the blockchain is shown in Figure 1.The structure of a blockchain can be described as a block which consists of multiple transactions and is connected with a previous block in a chain-like form. A blockchain consists of a series of blocks. The blocks are connected by the cryptographic hash function of the previous block. A block is made of a block head and a block body. The block head encapsulates the current block version number, the hash value of the previous block, Merkle hash tree root, nonce, difficulty value and timestamp information. Merkle Hash Tree (MHT) is constructed by calculation results based on a hash function (i.e. SHA256). The Merkle hash tree root is the hash of all transactions in this block to prevent the adversary to tamper the data. The block body records a continuously growing list of transactions data, transaction information and the total number of transactions.