Oracle Magazine, Mar/Apr 2018
ORACLE MAGAZINE MARCH APRIL 2018 31 if it has been altered The block also contains the hash of the previous block which ties them together in a chain The backward hashing makes it extremely difficult for anyone to modify a single block without detection A chain contains collections of blocks which are stored on decentralized distributed servers the more the better with every server containing the same set of blocks and the latest values of information such as account balances Multiple transactions are handled within a single block using an algorithm called a Merkle tree or hash tree which provides fault and fraud tolerance if a server goes down or if a block or chain is corrupted the missing data can be reconstructed by polling other servers chains And while the chain itself should be open for validation by any participant some chains can be implemented with some form of access control to limit viewing of specific data fields That way participants can view relevant data but not everything in the chain A customer might be able to verify that a contractor has a valid business license and see the firms registered address and list of complaints but not see the names of other customers The state licensing board on the other hand may be allowed to access the customer list or see which jobs are currently in progress When originally conceived blockchain had a narrow set of protocols to govern the creation of blocks the grouping of hashes into the Merkle tree the viewing of data encapsulated into the chain and the validation that data has not been corrupted or tampered with Over time creators of blockchain applications such as the many competing digital currencies innovated and created their own protocols which due to their independent evolutionary processes werent necessarily interoperable By contrast the success of general purpose blockchain services which might encompass computing services from many technology government and business players created the need for industry standards such as Hyperledger a Linux Foundation project Hyperledger A Common Ground Many tech leaders and startups offer software or services for creating and using blockchain When their customers want to participate in a shared blockchain application such as to enable that farm to table vegetable tracking or logistics that use multiple trucking shipping
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