Multisig Setup Planner: 2-of-3 vs 3-of-5 Compared

Multisig Setup Planner (m-of-n)

A multisig wallet needs m signatures out of n keys to spend. That one number pair decides two risks pulling in opposite directions: losing too many keys locks the coins forever, and an attacker who gets m keys takes them. Enter m, n and your rough odds of losing or leaking a single key over ten years, and the planner shows both probabilities next to the common setups.

Setup	Keys you can lose	Keys an attacker needs	P(funds locked forever)	P(funds stolen)
1-of-1	0	1	10%	5%
2-of-2	0	2	19%	0.25%
2-of-3	1	2	2.8%	0.725%
3-of-5	2	3	0.856%	0.1158%
4-of-7	3	4	0.2728%	0.0194%

Setup

Keys you can lose

Keys an attacker needs

P(funds locked forever)

P(funds stolen)

1-of-1

10%

2-of-2

19%

0.25%

2-of-3

2.8%

0.725%

3-of-5

0.856%

0.1158%

4-of-7

0.2728%

0.0194%

The two numbers that matter

With m-of-n you can lose n − m keys and still spend, and an attacker must obtain m keys. A single-key wallet (1-of-1) has zero tolerance both ways. 2-of-2 doubles the attacker's work but makes loss worse: either key gone and the funds are stuck. 2-of-3 is the popular middle: one key can be lost, one can be stolen, and you still control the coins — as long as you notice and move funds before a second key goes.

The probabilities come from the binomial distribution: with an independent chance p of losing each key, the wallet is locked when more than n − m keys are lost; with a chance t of compromise per key, it is drained when at least m keys leak. The model's weak point is independence — read the next section before trusting small numbers.

P(locked) = Σ_{k=n−m+1..n} C(n,k)·p^k·(1−p)^(n−k)
P(stolen) = Σ_{k=m..n} C(n,k)·t^k·(1−t)^(n−k)

Making the keys really independent

Different places: keys in one home share one fire, one burglary and one search.
Different vendors: two hardware wallets from different manufacturers do not share a firmware bug or supply-chain attack.
Different people or roles in a family or company setup, so no single person can be pressured into signing alone.
A backup of the wallet descriptor (the xpubs, derivation paths and script type) with every key, or at least in several places. Without it, rebuilding an m-of-n wallet is hard even with all the seeds.

When multisig is worth the effort

Multisig adds steps to every spend and needs wallet software that supports it — Sparrow, Electrum, Nunchuk, Specter and others for Bitcoin; Safe for Ethereum and EVM chains. It pays off for long-term savings, shared treasuries and inheritance plans where a single seed phrase would be a single point of failure. For everyday amounts, one well-backed-up hardware wallet is simpler and the risk of mistakes is lower.

Exchanges and swap services such as KOT.CASH pay out to a normal address of your wallet; for a Bitcoin multisig that address is generated by your multisig software and works like any other P2WSH or P2TR address.

Frequently asked questions

+Is 2-of-3 better than one hardware wallet?

For large savings, usually yes: it survives the loss of one key and the theft of one key. The cost is complexity — you must back up three keys and the wallet descriptor correctly.

+What are realistic loss and theft odds?

Nobody knows exactly; the inputs are for comparing setups. Try pessimistic values such as 10–20% loss and 5–10% compromise per key over ten years and see how each setup behaves.

+Can I use multisig for USDT?

On EVM chains a smart-contract wallet such as Safe implements m-of-n for any token. TRON has native multi-signature permissions. The planning logic is the same.

+Does the planner touch my keys?

No. It only does arithmetic on the numbers you type. Never enter seed phrases or private keys into any website.

+What happens if one co-signer dies?

In 2-of-3 the remaining two keys can still spend. That is why multisig is popular in inheritance plans — combine it with clear instructions for heirs.

Calculations run entirely in your browser; nothing you type is sent to KOT.CASH. Results are estimates for information only and are not financial, tax or legal advice.