BLOCKCHAIN & WEB3 FUNDAMENTALS - Chapter 1, Exercise 1 Solution
==========================================================
Naming the Trusted Third Party in Everyday Digital Systems

PROBLEM
-------
List three real digital payment or messaging systems you use regularly.
For each, name the single trusted party whose ledger or server is the
one authoritative source of truth, and describe what would go wrong for
you personally if that party became unavailable or dishonest.

SOLUTION
--------
This exercise has no single "correct" three systems - the point is
correctly identifying the trusted party and its real failure mode for
each one you pick. A representative worked example, using three common
systems:

1. A BANKING APP (e.g. checking a current account balance)
   Trusted party: the bank itself. Your account balance is not stored
   on your phone - it's a number in the bank's own private database.
   Your app just displays whatever that database says.
   If unavailable: you can't check your balance, move money, or pay
   anyone until the bank's systems are back up - a real, documented
   category of outage banks occasionally suffer.
   If dishonest: the bank could, in principle, misreport your balance,
   freeze your funds, or reverse a transaction, and you would have no
   independent way to prove otherwise - you'd be relying on their
   record being the "true" one, because it's the only one that exists.

2. EMAIL (e.g. Gmail, Outlook)
   Trusted party: the email provider. Every message you send or
   receive passes through, and is stored on, their servers.
   If unavailable: you simply can't send or receive mail until service
   is restored.
   If dishonest: the provider could read, alter, or selectively deliver
   your messages, since nothing about plain email cryptographically
   proves a message wasn't tampered with in transit or storage.

3. A CARD NETWORK (e.g. paying with a debit/credit card in a shop)
   Trusted party: the card network and the two banks involved (yours
   and the merchant's).
   If unavailable: the transaction simply fails at the point of sale -
   a real, occasionally-reported category of outage.
   If dishonest: a network or bank could, in principle, decline a
   legitimate transaction or delay settlement, and the merchant/
   customer has no way to independently verify or override the
   network's own decision.

ANSWER: In every case, one specific organization's own private servers
are the single source of truth, and both "unavailable" (an outage) and
"dishonest" (misreporting, censoring, or reversing something) are real
risks that exist purely because there's exactly one party being
trusted, with no independent way to check their record against anyone
else's.

----
WHY THIS WORKS AS AN ANSWER

This directly applies the chapter's own core distinction - a single
trusted third party keeping the one authoritative ledger - to systems
the reader already uses daily, making the abstract "trust problem" from
the chapter concrete before any blockchain mechanics are introduced.