Ledger

What Is a Ledger?

A ledger is a record of financial or data transactions, traditionally kept as a physical book and now more commonly maintained as a digital file.

A ledger lists debits, credits, balances, and the dates of each entry. Physical ledger books predate modern banking, while today most ledgers are digital, maintained by businesses, governments, and financial institutions to track money flowing in and out.

In cryptocurrency, blockchains function as a particular kind of digital ledger, and understanding what makes them different helps clarify how they work.

How Do Traditional and Digital Ledgers Differ?

A traditional ledger records transactions in sequence, with each entry listing the amount, the parties involved, and the date, and updating account balances. A central party such as a bank, accountant, or business has the authority to add, correct, or delete entries.

Digital ledgers in everyday business operate similarly: accounting software, banking systems, and enterprise resource planning (ERP) platforms are all digital ledgers. Their central management is efficient, but errors, fraud, or data breaches at the central authority can affect the entire record.

What Is a Blockchain Ledger?

A blockchain is a digital ledger that stores transaction data in blocks, where each block is linked to the previous one using cryptographic hashing. Altering an earlier record would require recalculating every subsequent block, making unauthorized changes computationally prohibitive under normal network conditions.

What Is Distributed Ledger Technology?

Distributed ledger technology (DLT) refers to any system where a shared record is maintained simultaneously across multiple nodes rather than a single central server. Blockchain is the most widely known type of DLT, but it is not the only one.

Other DLT structures include:

• Directed Acyclic Graph (DAG): Instead of blocks in a chain, transactions form a graph where each new transaction validates earlier ones. This structure can support higher throughput in certain use cases.
• Hashgraph: Implemented by Hedera, this is a type of DAG that uses a "gossip-about-gossip" protocol and a virtual voting algorithm. Nodes achieve rapid, secure consensus locally without needing to broadcast heavy voting messages across the network.

Each structure involves trade-offs in speed, decentralization, and the type of data it handles most efficiently.

DLT networks can also be categorized by who is permitted to participate:

• Public: Open to anyone. Bitcoin and Ethereum let any participant read data, submit transactions, or run a node.
• Private: Access is restricted to authorized participants, used by businesses for internal record-keeping, auditing, and sensitive data management.
• Consortium: A group of organizations shares the ledger, common in banking, trade finance, and supply chain logistics where multiple parties need a shared record but full public access is not appropriate.

What Are Real-World Uses of DLT Ledgers?

DLT-based ledger systems are in active use across multiple industries:

• Supply chain: Tracking the origin and movement of goods with a shared, tamper-evident record.
• Healthcare: Securely sharing patient records among authorized providers while maintaining data integrity.
• Finance: Automating cross-border payments and securities settlement between institutions.
• Public sector: Managing land registries, voting records, and identity verification.