Question — Q.86
Which of the following statements regarding the features of blockchain technology are correct?
1Records 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.
3Consortium 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.
A1 and 3
B2 and 4 only
C1, 2 and 4 ✓
D1 and 4 only
Each Statement — Blockchain Fundamentals Verified
1
✓ Correct — Transparency + Immutability
Records may be made visible to relevant stakeholders without risk of alteration
Correct. This describes two core blockchain properties together:• Transparency: In a public blockchain, all records are visible to anyone. In private/consortium blockchains, records are visible to relevant/authorised stakeholders (the “relevant” qualifier accounts for all blockchain types).
• Immutability: Once data is recorded and accepted into the blockchain, it cannot be altered — the cryptographic hash of each block links it irrevocably to the previous block. Any alteration would change the hash and invalidate the chain.
The combination of these two properties — transparency to relevant stakeholders + zero risk of alteration — is a defining feature of blockchain.
✓ Blockchain feature: Transparency (visibility) + Immutability (no alteration)
“Relevant stakeholders” covers all blockchain types (public = anyone, private = members, consortium = pre-approved group)
2
✓ Correct — Distributed Ledger Technology
Copies of the entire database are stored on multiple computers on a network, syncing within seconds
Correct. This is the definition of a Distributed Ledger — the most fundamental property of blockchain:• Every participant (node) in the blockchain network maintains a complete copy of the entire blockchain database.
• When a new block is added (a new transaction is verified), all copies across the network are updated and synchronized rapidly.
• This decentralisation means there is no single point of failure and no central authority controlling the data.
The “syncing within seconds” reflects the near-real-time propagation of new blocks across all nodes in the peer-to-peer network.
✓ Blockchain’s Distributed Ledger Property — all nodes hold full copy
Peer-to-peer network · Every node = complete copy · New blocks propagate rapidly across all nodes · No central server · No single point of failure
3
✗ Inaccurate — “Blend of public and private” describes Hybrid, not Consortium
Consortium blockchain is a blend of public and private blockchains allowing selective data access
Statement 3 contains a technically imprecise description that UPSC treats as incorrect:What Consortium blockchain actually is: A semi-private/semi-decentralised blockchain controlled by a pre-approved group of organisations (e.g., a group of banks, healthcare providers, or logistics companies). It is NOT open to the public — access is restricted to verified members. Control is shared among multiple organisations rather than being held by a single entity (as in a private blockchain).
The precise “blend” distinction: The description “blend of public and private blockchains” technically and more accurately describes Hybrid Blockchain — which can have both a public chain (permissionless) and a private component. A consortium blockchain is closer to a permissioned private blockchain with shared governance among multiple entities.
Selective data access — this part is correct for consortium blockchain (members can access data, non-members cannot). But the “blend of public and private” framing is what makes Statement 3 inaccurate per UPSC.
✗ “Blend of public and private” = Hybrid Blockchain · Consortium = semi-private with shared governance
Consortium: Pre-approved member organisations control it · Multiple entities share authority · Similar to private blockchain but distributed among multiple organisations · No public access
4
✓ Correct — Cryptographic immutability
Mathematical algorithms make it impossible to change or delete any data once recorded and accepted
Correct. This describes blockchain’s immutability property, enforced through:• Cryptographic hashing (SHA-256 etc.): Each block contains the hash of the previous block. Changing any data in an old block changes its hash, which invalidates the hash stored in the next block, causing a cascade of invalidations throughout the chain.
• Consensus mechanisms: For a change to be accepted, it would require consensus from the majority of nodes simultaneously — computationally infeasible in large networks.
• Merkle trees: Mathematical structure linking all transactions within a block, making tampering detectable.
The result is that once a block is confirmed and added to the chain, altering or deleting its data is computationally infeasible — effectively “impossible” in practice.
✓ Cryptographic immutability — SHA-256 hashing + Consensus mechanisms
SHA-256 hash of each block links to previous block · Merkle trees link transactions within blocks · Changing one block invalidates all subsequent blocks · Consensus of majority nodes required to accept any change
Four Types of Blockchain — Key Distinction for UPSC
| Type | Who controls? | Access | Best described as |
| Public | No single entity — fully decentralised | Anyone can join, read, write | Fully open, permissionless (Bitcoin, Ethereum) |
| Private | Single organisation controls | Restricted to invited participants only | Centralised but with blockchain structure |
| Consortium | Group of pre-approved organisations (not public) | Restricted to approved member organisations only — NOT public access | Semi-decentralised, multi-entity controlled — closer to private than public |
| Hybrid | Mixed — some parts public, some private | Public part = open; Private part = restricted | “Blend of public and private” — this description fits Hybrid, not Consortium |
Memory Trick
🧠 Four Blockchain Properties — P.D.I.C.
P = Permissionless / Transparency (St.1): Records visible to relevant stakeholders without alteration risk. “Relevant” makes it true for all blockchain types — public (anyone) or private (members).
D = Distributed (St.2): Distributed Ledger = full copy on every node = no central server. New blocks sync across all nodes rapidly. This is blockchain’s most defining structural property.
Statement 3 trap — Consortium ≠ “blend of public+private”: Hybrid = blend of public and private. Consortium = multi-organisation shared governance of a permissioned (restricted) blockchain. Remember: Consortium is not open to the public — it’s like a private club of organisations.
I = Immutability (St.4): Mathematical algorithms = cryptographic hashing (SHA-256) + consensus = computationally infeasible to alter recorded data. Once accepted into the chain, data is permanent.
