ECO349H5 Chap.6 Payment Systems and Cryptocurrency
Payment Systems and Cryptocurrency
Verification before valuation
A payment system updates claims after an exchange. Before comparing technologies, identify the asset being transferred, the ledger that records ownership, the party that validates instructions and the rule that makes settlement final.
A fast message is not necessarily final settlement, and a familiar interface does not reveal whether the underlying claim is commercial-bank money, central-bank money or a privately issued token.
Trace a transaction end to end
A payer creates an instruction, proves authority over the relevant balance and sends the instruction for validation.
The system checks signatures, available balances and consistency with previous records. Valid transactions are ordered, the ledger is updated and recipients decide when the result is irreversible enough to treat as final. Writing this sequence exposes where operational, fraud and reversal risks enter.
Centralized systems assign validation and ledger maintenance to designated institutions.
Distributed ledgers coordinate multiple validators through protocol rules. Distribution can change resilience and governance, but it does not eliminate trust; users still rely on software, incentives, key management and the rule for resolving competing histories.
Evaluate the complete institution rather than treating one database structure as the payment asset itself.
Model security as an incentive
A stylized attack condition compares expected incremental recovery from manipulating the ledger with the cost of the attack. Expected benefit depends on the amount recoverable, any fee or double-spend gain and the probability of success.
Security improves when expected benefit falls or attack cost rises. Show the inequality and explain the margin rather than asserting that computation automatically guarantees honesty.
The model is deliberately partial. Repeated attacks, detection, legal sanctions, token-price effects and strategic responses can change the calculation.
A numerical result therefore establishes profitability under the supplied assumptions, not universal safety. Sensitivity analysis should vary the transaction value, success probability and cost separately and identify the threshold at which behaviour changes.
Classify digital monetary claims
A cryptocurrency without a redemption promise differs from a stablecoin that claims a fixed conversion into another asset.
For the stablecoin, reserve composition, custody, redemption priority and liquidity during mass withdrawals matter. One-for-one language is not proof that safe liquid backing is available immediately.
For a central-bank digital design, the issuer and settlement claim differ again, along with questions about access and privacy.
Compare designs across a common grid: issuer, verifier, asset backing, settlement rule, access, governance and principal failure mode. This prevents convenience, monetary value and ledger security from collapsing into one score.
A system may settle efficiently but expose users to issuer risk, or offer a robust monetary claim while concentrating operational control.
Evaluate policy against an objective
Begin an application answer by naming the problem: settlement delay, cost, exclusion, privacy, resilience or monetary sovereignty. Explain which feature of the proposal addresses it.
Then identify new risks, such as reserve runs, validator concentration, key loss or surveillance. The conclusion should be conditional on the objective and institutional safeguards, not a claim that one architecture dominates every use.
Market statistics for token price, energy use or throughput can become stale. Use them only with a date and a clear analytical role.
The durable course mechanisms do not require decorative numbers: validation must deter profitable attacks, redemption depends on backing and liquidity, and governance determines how rules change. Revision should therefore prioritize the transaction sequence, the no-attack inequality and the comparison grid.
What this chapter covers
- 01
Payment ledgers
- 02
Blockchain validation
- 03
Double spending
- 04
Stablecoins
- 05
Settlement finality
Worked example · free
When an attack does not pay
- 2Multiply the recoverable amount by the probability that ledger manipulation succeeds.
- 2Compare incremental expected recovery with the resource cost of mounting the attack.
Key terms
- Blockchain
- A Blockchain is a distributed ledger extended through protocol-governed validation of transaction blocks.
- Redemption
- Redemption exchanges a monetary claim for its promised underlying asset or currency.
Payment Systems and Cryptocurrency FAQ
Is blockchain a store-of-value payment system?
The course treats blockchain as a decentralized account-based ledger because ownership transfers are verified against recorded balances. A token may also be held as a store of value, but that use is separate from the ledger architecture.
What prevents a double spend?
Validation rules, accumulated work or stake, confirmation practices and the cost of rewriting history make attacks harder. The simplified model compares probability-weighted recovery with attack cost, while real systems involve more channels.
What keeps a stablecoin near its peg?
Credible redemption, liquid backing, transparent reserves and issuer governance support the reference value. A stated peg without sufficient accessible assets can fail under concentrated redemption demand.
Exam move
Trace the ledger sequence, solve the security inequality, then compare three designs across verifier, issuer, backing and failure mode.
Working through Payment Systems and Cryptocurrency in ECO349H5? Sia is AskSia’s AI Economics tutor — ask any ECO349H5 Payment Systems and Cryptocurrency question and get a clear, step-by-step explanation grounded in how ECO349H5 is taught and assessed. Read this chapter free, then take your hardest questions to Sia.
