Tamper-Proof Ledger

A tamper-proof ledger is a record of transactions or data built so that once an entry has been written, nobody can quietly change or remove it. The phrase is used most often to describe blockchains and other forms of distributed ledger technology. In a blockchain, each block contains a cryptographic hash of the previous one, so altering an old record would change every later hash and be obvious to anyone checking. Because many independent participants hold copies and must agree on additions, a forger would also need to overpower the network's consensus. Specialists often prefer the term tamper-evident, since determined attackers with enough control, or the operators of a private ledger, can still rewrite history; what the design guarantees is that tampering is detectable, not that it is impossible. Also see immutability and cryptographic immutability.