UPSC Prelims 2026 Q86: Blockchain Features & Types — Explained
Which of the following statements regarding the features of blockchain technology are correct?
1. Records stored in the database may be made visible to relevant stakeholders without risk of alteration.
2. Copies of the entire database are stored on multiple computers on a network, syncing within seconds.
3. Consortium blockchain is a blend of public and private blockchains allowing selective data access.
4. Mathematical algorithms make it impossible to change or delete any data once recorded and accepted.
- 1 and 3
- 2 and 4 only
- 1, 2 and 4
- 1 and 4 only
Answer: (c) 1, 2 and 4
Statement-wise explanation
- 1: correct — Blockchain is a shared ledger. Participants who are given access can read the records, but they cannot quietly change them. Every block carries a cryptographic hash of the block before it, so editing any record breaks the chain and the other nodes reject it. This mix of openness and protection from tampering is why governments use blockchain to verify documents and land records.
- 2: correct — Blockchain is a type of distributed ledger technology (DLT). Each node, meaning each computer on the network, keeps a full copy of the ledger. When a new block is accepted through consensus, it is sent across the network and every copy updates. No single central database exists that could fail or be secretly edited.
- 3: incorrect — 'A blend of public and private blockchains allowing selective data access' is the standard definition of a hybrid blockchain. A hybrid blockchain runs a private, permissioned part alongside a public part and decides which data is made public. MeitY's National Blockchain Framework describes a consortium blockchain differently: it is semi-decentralised and governed jointly by several organisations, which share data management and validation. The statement gives the right definition to the wrong type.
- 4: correct — This statement describes immutability, the defining feature of blockchain. Cryptographic hashing links every block to the one before it. Consensus algorithms then require most of the network to accept each block. Once data is recorded and accepted, changing or deleting it would mean rewriting every later block on most copies of the ledger, which is treated as practically impossible.
How to eliminate
Start with statement 3. It is the only statement about a type of blockchain, not a feature. 'Blend of public and private with selective data access' is the textbook definition of a hybrid blockchain. A consortium blockchain is defined by shared governance among several organisations. If you are sure statement 3 is wrong, options (a) and the earlier choice built on 1 and 3 drop out. What remains is: 2 and 4 only, 1 and 4 only, or 1, 2 and 4. Statements 1, 2 and 4 are the three standard features of blockchain: transparency to authorised users, a distributed ledger, and immutability. Basic knowledge is enough to accept all three. The word 'only' in the other two options should make you check whether statement 1 or 2 is really false, and neither is. Statement 4 says 'impossible', and absolute words usually signal a false statement. Here, though, 'impossible to change' is how official and textbook sources describe immutability, so do not reject it for that word alone. The fact to remember: hybrid = public + private blend; consortium = run by several organisations.
Know more
Blockchain is a type of distributed ledger technology (DLT). Records are grouped into blocks. Each block stores a cryptographic hash of the block before it, which links the blocks into a chain. A consensus mechanism decides which new block every node accepts. Three properties follow from this:
- Decentralisation: every node holds a copy of the ledger, so there is no single point of failure.
- Transparency: authorised participants can view and verify records.
- Immutability: changing one block breaks every hash after it, so accepted data is effectively permanent.
Types of blockchain
| Type | Who can join / validate | Control | Typical use |
|---|---|---|---|
| Public | Anyone (permissionless) | Fully decentralised | Bitcoin, Ethereum |
| Private | Selected participants only (permissioned) | One organisation | Internal enterprise or government records |
| Consortium | Selected nodes from several organisations | Semi-decentralised, jointly governed | Inter-bank settlement, supply chains |
| Hybrid | Private permissioned part + public part | One entity decides which data goes public | Selective disclosure, e.g. records verifiable on request |
Common traps
- Consortium ≠ hybrid. Consortium is about who governs (several organisations). Hybrid is about architecture (a public part plus a private part).
- Blockchain ≠ cryptocurrency. Crypto is one use of blockchain. India's government projects use permissioned, non-crypto blockchains.
- A CBDC is a central bank liability. It does not have to run on blockchain.
India's context: MeitY has built a National Blockchain Framework (NBF), a common architecture for blockchain-based public services. In February 2026 it launched the Blockchain India Challenge for startups. The challenge focuses on permissioned blockchain for the public distribution system, land records, document verification and healthcare data.
In the news
On 23 February 2026, MeitY launched the Blockchain India Challenge, a startup contest for permissioned, non-crypto blockchain solutions in governance. Its launch followed a PIB backgrounder on the National Blockchain Framework that explained public, private and consortium blockchains. Together these put blockchain features and types in the news before the 2026 Prelims.
NCERT Concepts to Revise
- Blockchain: Every statement tests a property of blockchain as a distributed ledger, such as visibility, replication, immutability or network type.