Blockchain

1. Meaning and technological foundations

A ledger is a record of transactions or changes in ownership and status. In a conventional database, one institution usually controls the authoritative record. A distributed ledger allows multiple network participants to maintain synchronised records according to common rules. Blockchain is one implementation: transactions are grouped into blocks, with each block normally containing a cryptographic reference to the preceding block. This creates a linked history whose unauthorised alteration can be detected.

A cryptographic hash converts input data into a fixed-length output. Changing the input normally changes the resulting hash, making hashes useful for checking integrity. Hashing is not encryption: it is not designed to be reversed to recover the original message. Linking blocks through hashes means that modifying an earlier record would disturb subsequent links. However, preventing acceptance of an altered history also depends on consensus rules, network participation and operational security.

Public-key cryptography supports transaction authorisation. A private key is used to create a digital signature, while the corresponding public key enables verification. A signature demonstrates authorisation by the relevant key-holder; it does not automatically prove a person's legal identity. Losing a private key may mean losing access to assets, while theft of the key can allow fraudulent transactions. Cryptographic strength therefore does not eliminate human or institutional vulnerabilities.

• Node: a computer participating in the network; nodes may store records, relay transactions or validate them.
• Consensus: the rules and mechanisms through which participants agree on valid transactions and ledger state.
• Finality: the point at which a transaction is treated as settled; its strength and timing vary across blockchain designs.

2. Network types and consensus mechanisms

Public, private and consortium describe broad governance or accessibility arrangements, while permissionless and permissioned refer to whether authorisation is required for particular activities. A public permissionless network generally allows open participation under its protocol rules. A private network is controlled by an organisation, while a consortium network is governed by several organisations. Reading data, submitting transactions and validating blocks can each have different access conditions; a publicly readable ledger can still restrict validation.

Proof of work requires miners to perform computational work to propose blocks. Bitcoin uses this mechanism, and its security model involves substantial electricity consumption. Proof of stake selects or weights validators using assets committed as stake; protocol-specific penalties may discourage misconduct. Ethereum moved from proof of work to proof of stake in September 2022 through an upgrade known as the Merge. Neither mechanism is essential to all blockchains.

Permissioned systems may use voting-based, Byzantine fault-tolerant consensus among identified validators. These can provide rapid settlement with relatively low energy use, but their security rests on assumptions about validator behaviour and governance. Decentralisation is therefore a matter of degree. Mining-pool concentration, validator concentration, software control and cloud dependence can create power centres even in nominally decentralised networks.

• Mining is associated with proof-of-work systems; it is not a universal blockchain activity.
• A majority attack can enable censorship or reorganisation in some networks, but does not automatically reveal private keys or permit arbitrary spending from every account.
• Forks are divergences in chain history or protocol rules; they show that blockchain governance remains a technical and social process.

3. Smart contracts, tokens and applications

A smart contract is program code that executes on a blockchain when specified conditions are satisfied. It can automate escrow, payments or transfers of tokenised assets. The term does not mean that the program is intelligent or necessarily a legally enforceable contract. Programming errors, flawed incentives and stolen administrative keys can cause major losses. Execution is only as dependable as the code, inputs and surrounding governance.

An oracle supplies external information, such as a market price or weather observation, to a blockchain application. This creates the oracle problem: agreement within the ledger does not guarantee the reliability of outside facts. Similarly, recording a food consignment's origin cannot prevent someone from initially entering false information. Physical inspection, accredited certification and liability rules remain necessary.

Cryptocurrency is one blockchain application, not a synonym for the technology. Tokens can represent payment units, access rights or claims on assets. A non-fungible token represents a distinguishable token rather than an interchangeable unit, but owning one does not automatically transfer copyright or ownership of an associated physical object. Useful non-currency applications include credential verification, shared trade documentation, provenance records and inter-institutional reconciliation.

• Digital certificates can place a document's hash on a ledger while keeping the document itself off-chain.
• Supply-chain systems can record successive transfers, but must securely connect digital records with physical goods.
• A central bank digital currency is a central bank liability and need not use blockchain; digital payment systems such as UPI are not cryptocurrencies.

4. Indian initiatives and regulatory context

The Ministry of Electronics and Information Technology released the National Strategy on Blockchain in December 2021. It envisaged shared infrastructure, standards, research and capacity-building for trusted digital platforms. In September 2024, MeitY launched the National Blockchain Framework. Its Vishvasya component provides blockchain-as-a-service through a geographically distributed infrastructure for permissioned applications. The launch also included the NBFLite sandbox for learning, experimentation and prototyping.

The National Informatics Centre has developed blockchain capabilities for government use cases, including document verification. CBSE's Academic BlockChain Documents initiative illustrates how educational records can become easier to authenticate. Such systems can reduce repeated verification and expose tampering, but cannot substitute for the authority responsible for issuing or correcting certificates.

India's treatment of virtual digital assets must be separated from its support for blockchain technology. The Finance Act, 2022 introduced section 115BBH of the Income-tax Act, providing a 30 per cent tax rate on income from transfer of virtual digital assets, subject to statutory rules. Section 194S provides for 1 per cent tax deduction at source on consideration for specified transfers, subject to thresholds and conditions. Taxation does not confer legal-tender status.

A March 2023 notification brought specified virtual-digital-asset service activities within the Prevention of Money Laundering Act framework. Covered service providers face obligations such as customer due diligence, record maintenance and reporting. The RBI's e₹ pilots began in 2022; the digital rupee is distinct from privately issued cryptoassets because it is issued by the central bank.

• For Prelims, distinguish the technology policy of MeitY from the monetary role of RBI and anti-money-laundering supervision involving FIU-IND.
• Recording land information on a blockchain does not itself resolve disputed titles or change the applicable property law.

5. Benefits, limitations and suitability

Blockchain's principal value is a shared, verifiable record among organisations that need coordination but do not wish to give one participant complete control. Potential benefits include reduced reconciliation, traceable updates and automated execution. Nevertheless, a conventional database may be cheaper, faster and easier to correct when one trusted authority already manages the entire process.

The description immutable should be understood as resistant to unauthorised alteration under stated assumptions, not impossible to change. Protocol upgrades, reorganisations, compromised keys and collusion can affect outcomes. Public blockchains are also generally pseudonymous rather than anonymous: addresses may be linked to individuals through transaction analysis or exchanges. Encryption of all transaction data is not an inherent blockchain feature.

Other concerns include limited throughput, transaction fees, interoperability, software vulnerabilities and uncertain responsibility across jurisdictions. Replication of personal data can conflict with data minimisation and correction requirements. Privacy-conscious designs therefore often keep sensitive information off-chain. India's Digital Personal Data Protection Act, 2023 is relevant when designing systems that process digital personal data. Adoption should follow a clear assessment of the problem rather than an assumption that decentralisation is always desirable.

• Ask whether several parties need to write to a common record and whether they can rely on a single accountable intermediary.
• Evaluate energy consumption by consensus mechanism rather than attributing Bitcoin's energy profile to every blockchain.
• Define correction procedures, dispute resolution, key recovery and accountability before deployment.

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