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Clear out junk files and repair common Windows errorsFree Scan →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →A blockchain is a shared digital ledger that stores records in blocks, links those blocks cryptographically, and uses network rules to agree on which new records to accept. That can make old records difficult to alter without detection, but it cannot prove that the information entered was true or make blockchain the right choice for every database.
What is blockchain, in plain English?
Think of a digital record book shared among a group of computers. New entries are collected into blocks—similar to pages—and each block contains a cryptographic link to the one before it. Participants follow the network’s rules to check and accept new blocks. If someone changes an older entry, the link no longer matches, making the alteration detectable. As additional blocks build on that history, changing earlier records becomes harder under the system’s rules.
This is an analogy, not a literal paper book. Blockchain networks differ in who can participate, who validates records, what information is visible, and how participants agree. NIST describes blockchain as a way for a community to maintain a shared, tamper-evident and tamper-resistant digital ledger. “Tamper-resistant” does not mean impossible to change.
How does a blockchain work?
- A participant proposes a record. Depending on the system, this might represent a transaction or another kind of data.
- The network checks it. Participants or designated validators apply the network’s rules to decide whether the proposed record is acceptable.
- Accepted records are grouped into a block. The network uses a consensus process to determine which block becomes part of the shared history. The specific process varies by blockchain.
- The block links to earlier history. Its cryptographic link helps reveal later attempts to alter it or the records before it. In systems where more blocks are added, changing an older record may also require changing subsequent links and overcoming the network’s rules.
Bitcoin illustrates one specific design: transactions are signed with a private key, broadcast to the network, and confirmed when included in a block. Bitcoin uses mining as its consensus process; mining is not a requirement of every blockchain. Bitcoin.org’s explanation of how Bitcoin works describes those Bitcoin-specific steps.
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Blockchain, cryptocurrency and distributed ledgers: what is the difference?
- Blockchain versus cryptocurrency: Blockchain is a ledger technology used by many cryptocurrency systems, but it can also support other kinds of applications. Bitcoin is one cryptocurrency system that uses a blockchain; the terms are not interchangeable.
- Blockchain versus distributed ledger technology (DLT): Blockchain is one way to organize a distributed ledger. DLT is a broader category for systems that synchronize records across computers; some use structures other than blocks linked in a chain. The Bank for International Settlements overview of distributed ledger technology discusses these distinctions.
- Blockchain versus a conventional database: A conventional distributed database may rely on an administrator to coordinate updates and maintain a master copy. Some blockchain designs instead use agreement among participants to maintain shared records without one trusted central authority. Whether that difference matters depends on how a system is governed and what the application needs.
What blockchain can—and cannot—guarantee
A blockchain can help participants share a record and detect whether accepted history has been altered. It does not establish that the original entry was accurate. If someone records a false claim or makes a mistake, cryptographic links do not turn that claim into truth. And where a network makes records difficult to change, correcting an accepted mistake can take considerable effort.
Some systems also place responsibility for access on users’ private keys. NIST notes that losing a key can mean losing access to associated assets, while a stolen key can let an attacker control them. These key-related risks apply where users manage keys; they are not a universal feature of every blockchain application. NIST’s testimony on blockchain applications discusses these limitations.
Where might blockchain be useful?
NIST identifies potential applications such as manufacturing supply chains, data registries, digital identification and records management. These are possible uses, not proof that blockchain is the best solution for each one. The case is strongest when multiple participants need a shared record and the governance model makes a single record keeper undesirable or unsuitable. If a trusted administrator can maintain a conventional database effectively, adding blockchain may not provide enough value to justify its costs or complexity.
Trade-offs depend on the design. The BIS describes Bitcoin’s proof-of-work blockchain as costly to operate, with probabilistic finality and public transactions—properties that can make it unsuitable for many financial-market applications. Those are characteristics of Bitcoin’s design, not universal properties of all blockchains.
How to evaluate a blockchain design
Do not judge systems by the label alone. Compare the features that affect the actual use case:
- Participation and governance: Who may read, submit or validate records, and who sets the rules?
- Validation and consensus: How are records checked, and how does the network choose an accepted history?
- Privacy: What can participants or the public see?
- Finality: When should users treat a recorded transaction as settled, and can that status change?
- Performance and operating cost: Can the design meet the application’s needs without unacceptable overhead?
- Error correction and key management: How can mistakes be addressed, and who is responsible for protecting access credentials?
NIST’s Blockchain Technology Overview, NIST IR 8202, published in October 2018, provides a technical foundation for these concepts. The BIS overview is especially useful for understanding how ledger architectures and their trade-offs can differ.
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