# Comparative Study of Blockchain Hashing Algorithms with a Proposal for HashLEA
## 1 Introduction
The primary challenge blockchain faces when integrated into an IoT architecture is ensuring compatibility between the two domains, as it states that due to the nature of blockchain technology, which needs excessive resources for communicating with devices and performing validating and mining operations, quite a few IoT devices fail in terms of processing power, storage, and also engaged energy [15]. The other challenge is that IoT devices often have poor connectivity due to limited battery capabilities, while the blockchain typically is designed for stable network connections [16]. The consensus in blockchain technology basically provides for the participants' agreement on the validity of transactions and the order in which they shall be added to the blockchain [17]. Also, these protocols are considered crucial for maintaining the integrity of the blockchain ledger. Mining adds new blocks to the blockchain and generates new ones. Miners solve complex mathematical puzzles by using their computational power, and the first one to solve it gets to propose a new block of transactions to be added to the chain. This process is resource-intensive and requires a consensus mechanism to ensure that all participants agree on the validity of the proposed block. Hash functions are cryptographic algorithms that play a critical role in blockchain processes, such as generating and validating transaction signatures. By utilizing a hash function after a block is generated, each block is assigned a unique cryptographic hash value, with the latter being some sort of digital fingerprint that confirms the integrity of that block [18]. The Merkle root value is also computed by hash functions. The Merkle root is a summary hash that represents all the transactions within a block. It provides a compact and efficient way to verify the contents of a block without needing to process each transaction individually [19]. The blockchain uses specific computing conditions and high-power consumption schemes to implement cryptographic algorithms, in contrast to IoT devices, and that represents a challenge for resource-constrained IoT bias when implementing cryptographic algorithms in blockchain applications for these devices [20]. Cryptographic algorithms used in blockchain are classified into two major branches: symmetric and asymmetric encryption algorithms. The asymmetric encryption algorithms, like the RSA (Rivest-Shamir-Adleman) algorithm [21], are indispensable for ensuring the requisite level of security and privacy in the blockchain. RSA is one of the well-recognized asymmetric algorithms that are highly secure yet not suitable for IoT bias. The other limitation will be the tight limitations on the size of the RSA algorithm, which is believed to have a secure size of 2048 bits. ECC [22] has superseded the RSA algorithm due to its efficient integration with IoT devices, which manage to consume less energy and perform better than RSA. Because of the limited resources available in IoT devices, consensus protocols such as Proof of Work (POW) do not work well. The miner is elected through a process, namely the mining process, which requires significant computational effort to compute the hash in POW protocols [23]. Bitcoin uses SHA-256, a 256-bit secure hash algorithm that belongs to the SHA-2 family. The efficacy of SHA-256 has been assessed by a multitude of researchers across a spectrum of IoT devices [24], and it was concluded that its large size makes it undesirable for use in size- and power-constrained environments such as the IoT. For IoT devices, more efficient and compatible ciphers such as Lesamnta-LW and Simon [25] have been designed. A number of alternative hash functions have been proposed for use in blockchain-based applications, including Scrypt [26], the X11 [27] mining algorithm, and Blake [28], which are promoted as faster and requiring less power to mine. The hash function is selectively distinguished from each other--the hash function, in turn, will affect the latency and network availability problem during mining.