Learn in the textbookSecurity Testing and IoT / Hardware Protection
DefinitionA blockchain (ブロックチェーン) is a technology that bundles transaction records into "blocks," puts into each block a value calculated from the contents of the previous one (a hash value) so they link like a chain, and shares the resulting ledger among many computers.
ExplanationRewriting a past block changes its hash value, which then no longer matches the value stored in the block after it. The altered copy would also conflict with the records held by the many other participants, so tampering without being noticed is difficult. Blockchain began as the foundation of crypto assets and is now used to manage other kinds of transaction records too.
AnalogyLike everyone in a class keeping the same cashbook, with each page ending in a copy of the previous page's total. If one person rewrites an old page, it no longer matches the next page or anyone else's book, and the change shows at once.
Memory hookJust as the name says: blocks joined into a chain. The links of the chain are the hash values.