Blockchain

What does blockchain mean?#

NIST, the U.S. standards agency, defines blockchains as tamper evident and tamper resistant digital ledgers implemented in a distributed fashion — without a central repository — and usually without a central authority such as a bank, company or government^[1]. A ledger is simply a record of who holds what and who paid whom. "Distributed" means many computers, called nodes, each keep a copy instead of one company keeping the master version.

Bitcoin's white paper describes the core trick: the network timestamps transactions by hashing them into an ongoing chain, forming a record that cannot be changed without redoing the work that secured it^[2]. Every block header except the first contains a cryptographic link to the previous block^[1].

What does it look like with real numbers?#

Where will you see this term?#

You will meet the word wherever crypto assets are discussed: bitcoin, stablecoins and other tokens are all records on a blockchain. NIST notes that some blockchains are permissionless, where anyone can read and write, while others are permissioned and limit participation to specific organizations^[1]. A blockchain keeps records hard to alter; it does not make the assets on it valuable or safe.

For the full mechanism — hashes, blocks and consensus — read how blockchains work. To see what a token on a blockchain is, read what a crypto token is, and to understand who can move it, see private key.