Blockchains and ledgers
What a blockchain and a distributed ledger are, and what sets them apart from a database.
Start the chapter3 lessons
Lessons
- 01What is a blockchain?A blockchain is a record of transactions stored in batches called blocks. Each block carries a fingerprint, called a hash, of the block before it, and thousands of computers keep identical copies. Changing an old entry would break every link that follows it, which makes the record very hard to rewrite.
- 02What is a distributed ledger?A distributed ledger is a record of who owns what that many independent computers keep in full, with no master copy. Each new entry is checked by the participants and added to every copy in the same agreed order. A blockchain is the best known kind of distributed ledger, and other designs exist too.
- 03What makes a blockchain different from a database?An ordinary database is run by one owner, who can add, change and delete records in milliseconds. A blockchain is shared by many computers with no owner, and its records can only be added to. That makes it slower and more expensive, and worth using only when several parties need a record that none of them controls alone.