# Blockchain Interoperability for Future Telecoms
### History of Blockchain and Interoperability  
Blockchain networks were initially designed to function as standalone decentralized solutions. A decentralized approach eliminates trusted parties and provides an automatic and immutable system for proof of transactions. The idea of blockchain was first offered by the inventor of Bitcoin, [PERSON] [15], as a decentralized, public, permissionless, standalone, hashed block-based cryptographic proof system that eliminates trusted parties in the context of payment verification. There are two main types of blockchain systems: permissionless and permissioned. Permissionless blockchains operate as public networks and allow members to join without requiring approval. This design approach plays a significant role in decentralized blockchain solutions and serves as a reference blueprint for blockchain-based cryptocurrency solutions. As public permissionless blockchain designs initially focused on cryptocurrency and standalone networks, the demand for general blockchain interoperability was minimal until new popular cryptocurrencies, such as Ethereum [16], were launched. Meanwhile, three well-known challenges have emerged in this research area: security, flexibility in adaptation, and performance. According to [17], the Bitcoin consensus algorithm is a widely debated topic in the Bitcoin research community due to its stability, security, and concerns regarding computational resource wastage. Ethereum was developed and launched by [PERSON] et al. [10] in 2015 to address some of these challenges. It aimed to provide flexibility to cryptocurrency networks through the introduction of smart contracts [10], which enable more adaptable transaction processing. The introduction of smart contracts has facilitated the integration of enterprise rules and application usage. Through smart contracts, new enterprise-based features can be added to the current consensus mechanism, such as proof of work (PoW) and proof of stake (PoS). Finally, a new concept called decentralized applications (dApps) enables public blockchain networks to interact flexibly with other applications. dApps were introduced within Ethereum projects, allowing for interactions with centralized and decentralized external applications using smart contracts. The introduction of smart contracts and dApps has also facilitated extended use cases beyond cryptocurrency deployments and has become a significant use case for various industries. Although Ethereum is a more flexible solution, [PERSON] proposed Solana [17] in 2016 to provide more high-performance blockchain-based cryptocurrency networks to address well-known performance challenges. With the effect of the newly launched cryptocurrency networks, interoperability projects have emerged for public cryptocurrency-based blockchains. Such projects were primarily built to meet the growing demand for transferring or swapping cryptocurrency assets between networks. According to [18], over 10,000 blockchain networks had been reached by 2022, and significant amounts are still being built for public cryptocurrency projects. New cryptocurrency-based interoperability projects, such as Cosmos [19], Polkadot [20], and Overledger [21], have been launched to address asset and coin transfers and swaps. These projects were deployed as asset or coin transfers, which can only be achieved through interoperability, and aim to advance cross-industry blockchain technologies for enterprise use cases. In 2016, the Linux Foundation launched the Hyperledger project with 30 founding members in order to advance cross-industry blockchain technologies for enterprise use cases. The objective was to create an open-source framework for building distributed ledger solutions beyond cryptocurrencies. The Hyperledger project facilitated the enterprise-wide usage of blockchain, particularly for private, secure, permissioned networks. This initiative also prompted discussions on interoperability projects for industry and enterprise use, which is discussed in this article.