SMART CONTRACTS, DEFI & WEB3 SECURITY - Chapter 6, Exercise 3 Solution
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Why a 4-of-7 Multisig Beats a Single onlyOwner Address

PROBLEM
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Explain, using this chapter's own multisig explanation and Chapter 3's
own access-control material, why a 4-of-7 multisig is generally
considered safer for a DAO treasury than a single onlyOwner address —
and name one real trade-off this added safety comes with.

SOLUTION
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WHY IT'S SAFER

Chapter 3's own onlyOwner pattern restricts a sensitive function to
exactly one specific address, controlled by exactly one private key.
This chapter identifies the real problem with using that same pattern
for a large treasury: that one key becomes a genuine single point of
failure. If it's ever lost, stolen, or its holder acts dishonestly, the
entire treasury is immediately and permanently at risk, with no
possible recourse.

A 4-of-7 multisig, as this chapter describes, spreads that same
authority across seven independent keys instead of one, and requires
at least four of them to agree before any transaction can execute. This
directly addresses the single-point-of-failure problem: compromising or
losing any one, two, or even three of the seven keys still isn't
enough on its own to move funds, since a fourth independent signature
is still required. An attacker (or a single dishonest insider) would
need to compromise a real majority of genuinely independent signers,
not just one, which is a substantially harder real-world attack to
pull off.

THE REAL TRADE-OFF

This added safety comes at a real cost to speed and convenience.
Every transaction now requires coordinating at least four separate,
independent signers to actually review and approve it, rather than one
person simply acting unilaterally. This introduces real, genuine
friction and delay into every treasury decision - a legitimate,
time-sensitive action (like reacting quickly to an ongoing exploit)
could be meaningfully slowed down by needing to actually track down
and coordinate enough of the required signers in time, something a
single onlyOwner address wouldn't have any trouble with at all.

ANSWER: A 4-of-7 multisig is safer because it removes the single point
of failure a lone onlyOwner key represents - compromising any one, two,
or three keys alone still isn't enough to move funds, since a fourth
independent signature is required. The real trade-off is speed:
coordinating enough signers to approve a transaction takes real time
and effort, which can meaningfully slow down time-sensitive treasury
decisions compared to a single address that can act instantly and
unilaterally.

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WHY THIS WORKS AS AN ANSWER

This explains the specific mechanism (distributing trust across
multiple required signatures) that removes the single-point-of-failure
risk Chapter 3's own onlyOwner pattern carries, and names a real,
concrete cost (coordination delay) rather than presenting the multisig
as a strictly better option with no downside at all.