How blockchain manages and verifies data: HSC Enterprise Computing Data Science
“Explain how blockchain technology is used to manage and verify data, including online voting, online identities, tracking items of value and recordkeeping”
A blockchain is a distributed ledger of hashed blocks, each storing the previous block's hash and agreed by consensus, so changes are detectable. It verifies votes, identities, items of value and records, but it cannot guarantee data was true when entered and it clashes with privacy and efficiency needs.
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What this dot point is asking
You need to explain how blockchain technology stores and verifies data, then apply it to the four uses NESA names: online voting, online identities, tracking items of value and recordkeeping.
The answer
How a blockchain works
A blockchain is a distributed, append-only ledger.
- Records (transactions, events) are grouped into a block with a timestamp.
- The block is run through a hash function to produce its hash, a fixed-length fingerprint. Change one character of the data and the hash changes completely.
- Each block stores the hash of the previous block, chaining the blocks together.
- Copies of the ledger are held by many nodes (a distributed ledger), not one central database.
- Nodes use a consensus mechanism (proof of work, proof of stake or, in business systems, voting among approved members) to agree which new block is valid.
Tampering with an old block changes its hash, breaking the link to every later block, and the altered copy disagrees with all the other copies. Blockchain makes records tamper-evident and gives a trusted shared history without a single central authority.
Public blockchains (Bitcoin, Ethereum) let anyone participate. Permissioned blockchains limit validation to approved organisations and suit enterprises. Smart contracts are programs on the chain that run automatically when conditions are met.
The four applications
- Online voting. Each vote becomes a tamper-evident ledger entry that can be audited and counted quickly. The hard problems are voter identity, keeping ballots secret and device security before the vote is recorded.
- Online identities. Instead of every website holding your personal data, a trusted issuer (a university, a government agency) can record a verifiable credential. You prove a fact ("over 18", "holds a degree") without handing over every detail (self-sovereign identity).
- Tracking items of value. Supply chains record each handover of a product (diamonds, wine, pharmaceuticals, livestock) so buyers can verify provenance and spot counterfeits. Digital assets such as tokens are also tracked this way.
- Recordkeeping. Land titles, academic records, medical consent and audit logs benefit from a permanent, time-stamped history that several organisations can trust.
Limitations
- Garbage in, garbage out: blockchain proves a record has not changed since it was added, not that it was true when added.
- Immutability versus privacy: personal data on a chain is hard to correct or delete, which conflicts with privacy rights.
- Energy and speed: proof-of-work chains use large amounts of electricity and process fewer transactions per second than a normal database.
- Complexity and cost: for a single trusted organisation, an ordinary database with audit logs is usually simpler.
A university issues digital degree certificates.
- When a student graduates, the university records a hash of the certificate (not the personal details) on a permissioned blockchain shared with other universities.
- The graduate gives an employer the certificate file.
- The employer hashes the file and checks that the hash exists on the chain, issued by the university's key.
- A forged or edited certificate produces a different hash and fails the check.
This verifies the data without a phone call to the university and keeps personal details off the public ledger.
- Saying blockchain data cannot be hacked
- It is tamper-evident, but devices, keys and data entry can still be attacked.
- Equating blockchain with cryptocurrency
- Cryptocurrency is one application; the syllabus focuses on managing and verifying data.
- Ignoring when a normal database is better
- Blockchain adds value when several parties who do not fully trust each other share records.
Practice questions
Original practice questions graded from foundation to exam level, each with a full worked solution. Try them before revealing the solution.
foundation3 marksOutline how hashing links the blocks in a blockchain.Show worked solution →
Each block's contents are passed through a hash function to produce a fixed-length fingerprint (its hash). The next block stores this value as its "previous hash". Because any change to a block changes its hash, the stored link in the next block no longer matches, so the chain shows that tampering has occurred.
Marking guide: 1 mark for hash as a fingerprint of the block, 1 mark for the previous-hash link, 1 mark for why a change is detected.
core4 marksA wine exporter wants buyers in Asia to trust that its premium bottles are genuine. Explain how a blockchain could track these items of value from vineyard to buyer.Show worked solution →
Each bottle gets a unique ID (a QR code or NFC tag). At each step (bottling, export, customs, distributor, retailer) an authorised participant records an event on a permissioned blockchain with the ID, time, location and who handled it.
Because every record is hashed, time-stamped and replicated across participants, no single party can quietly change the history. A buyer scans the tag to see the full chain of custody. A counterfeit bottle has no matching history, or its ID shows it was already sold elsewhere.
Marking guide: 1 mark for unique IDs, 1 mark for events recorded by participants, 1 mark for tamper-evidence, 1 mark for how the buyer verifies.
exam6 marksEvaluate the use of blockchain for a national online voting system.Show worked solution →
- Benefits
- A blockchain gives a tamper-evident, time-stamped record of every vote, replicated across many nodes, so altering results after the fact would be detectable. Voters could receive a receipt to check their vote was counted, and results can be tallied quickly and audited publicly.
- Problems
- Voting needs both secrecy and verification of eligibility, which pull against each other on a transparent ledger. Blockchain only protects data after it is recorded: malware on a voter's device, identity fraud or coercion at home happen before the vote reaches the chain. Immutability means an incorrectly recorded vote cannot be easily corrected, and many voters would not understand or trust the technology. Security experts generally caution that online voting risks are not solved by blockchain.
- Judgement
- Blockchain improves the integrity and auditability of stored votes, but it does not solve identity, device security, secrecy or coercion, so it is not sufficient on its own for a national election. It may suit lower-stakes votes (a club or shareholder ballot) where convenience matters more and risks are smaller.
Marking guide: 2 marks for benefits, 3 marks for problems (secrecy, pre-chain attacks, immutability or trust), 1 mark for a justified judgement.