Blockchain Properties and Structure Forks A fork occurs if a block is added to a block that is not the most recent one Accidental if consequence of the consensus algorithm One fork survives;others are eventually orphaned Malicious if due to an attempt to damage the blockchain Consensus-based if agreed to by majority of users Consensus-based fork types Hard-old version of blockchain software does not recognize new blocks as valid Soft-old version of blockchain software recognizes new blocks as valid Database System Concepts-7th Edition 26.7 ©Silberscha乜，Korth and SudarshanDatabase System Concepts - 7 26.7 ©Silberschatz, Korth and Sudarshan th Edition Blockchain Properties and Structure ▪ Forks • A fork occurs if a block is added to a block that is not the most recent one • Accidental if consequence of the consensus algorithm ▪ One fork survives; others are eventually orphaned • Malicious if due to an attempt to damage the blockchain • Consensus-based if agreed to by majority of users ▪ Consensus-based fork types • Hard – old version of blockchain software does not recognize new blocks as valid • Soft – old version of blockchain software recognizes new blocks as valid