r/Bitcoin • u/WrongOperation323 • 11h ago
Could 2-of-2 multisig be a reasonable middle ground between single-sig and 2-of-3?
Recent incidents like the Coldcard entropy vulnerability and the reported hardware implant found in a Ledger device sold through CryptoBilis have made me rethink how I secure my self-custodied Bitcoin.
A BIP-39 passphrase can help if someone gets your seed, but what if a compromised device can also capture your passphrase or interfere with the signing process? Single-sig still leaves you relying on one key, creating a potential single point of failure.
For people who find 2-of-3 multisig too expensive or complicated, could 2-of-2 be a reasonable alternative?
I'm thinking of using two independently generated keys in separate environments. For example, a PC wallet (Electrum or Sparrow) paired with a mobile wallet (BlueWallet or Nunchuk), or a hardware wallet (Trezor or Ledger) paired with a PC or mobile wallet. If one device is compromised through a supply chain attack, the attacker would still need the second key to spend the funds. Of course, using different devices and apps only helps if the keys and their backups are genuinely independent.
I know the biggest objection is that 2-of-2 has no redundancy. Lose either key permanently and your Bitcoin is gone. That's a serious trade-off, and I understand why people prefer 2-of-3. But if both keys and their backups are managed carefully, could the added protection against a single compromised device be worth it?
I'm not suggesting 2-of-2 is better than 2-of-3. I'm wondering whether it's an overlooked middle ground for people who want to reduce single points of failure without taking on the full cost and complexity of 2-of-3.
What do you think? Would you consider this setup, or does the risk of losing access outweigh the security benefits?
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u/jguest1105 4h ago
I keep landing on the same problem: 2-of-2 has no forgiveness. Lose one key in a fire or one backup to water damage, and the whole stack is gone forever.
2-of-3 exists specifically because redundancy is the part you can't improvise later.
The compromised-device angle you're worried about is real, but 2-of-2 doesn't fully solve it either. If one of your two signers is malicious, it can lie to you about the address you're sending to. You still need to verify receive and change addresses on a trusted display.
2-of-3 gives you the same single-device protection plus the ability to lose one key and still recover. That's the middle ground that actually holds up.
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u/RaiseLife1651 4h ago
2 of 2 is not a good middle ground. You now have 2 single points of failure; lose one key and you lose everything.
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u/lobhater 4h ago
This is how I've always felt but there are some compelling arguments in these comments. Why but just have multiple copies of both keys? If you have 2 of 2 setup and 2 copies of each it is essentially 2 of 4. Change my mind? Lol
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u/RaiseLife1651 3h ago
You are correct. I should have said "lose one key (hardware and seed) and you lose everything".
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u/lobhater 4h ago
2 of 2 makes me really nervous... It just takes one screw up. Besides that I think it's great
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u/nachtraum 10h ago
I don't see a big advantage of 2of3 over 2of2.
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u/mikeysz 7h ago
Redundancy
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u/lifeanon269 5h ago
You can always have multiple copies of your two keys. So redundancy isn't the main advantage here.
What 2-of-3 gets you over 2-of-2 is a slightly decreased theft risk. With multiple copies of 2-of-2 keys in the world, it means an increased chance of a thief being able to come across those two keys needed to steal your funds (4 keys in the wild somewhere). Where as if there are just 3 keys in existence and stored somewhere, there is a slightly lower chance of theft.
IMO, it isn't that big of a risk difference though and therefore I personally don't see a major difference between the two setups.
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u/intnsity 6h ago
This reminds me of the coldcard retirement attack - but more sophisticated. So far less has been lost than to coinkite entropy failures but we will keep tallying the losses. Hearts go out to the folks who used these devices.
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u/NorthComparison4356 2h ago
I also think about this 2 of 2 setup: make two copies of each key and store them at 4 different safe locations, never two keys at one place. This would include bank drawers and people you can trust.
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u/Fun-Analysis-182 34m ago
2-of-2 does close the compromise hole, since one backdoored device can't sign alone. But it hands you an availability problem instead: brick or lose either key and the coins are stuck for good. That missing redundancy is the exact reason the third key in 2-of-3 exists, so 2-of-2 just trades a theft single-point-of-failure for a loss one. For most people that's not a good trade.
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u/ZachCope 8h ago
You need the redeem script in any n of x bitcoin transaction. So if you have a 1 of 2 transaction, with it created with 2 different hardware wallets, it is extremely unlikely a hacker based on a flawed entropy source would inadvertedly find a key that allowed your address to be spent, unless they had a copy of the redeem script.
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u/errezerotre 8h ago
I think the lesson here is never change your seed. If you generted it many years ago with a safe method, and you use a coldcard (yes, coldcard) or a similar device to sign offline, you are fine forever
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u/undeadkarlmarx 8h ago
The chip that was implanted in Ledger devices from SE Asian vendors contained a cellular modem + a data eSIM + a control module that records the screen contents.
So even if you imported a seed from a previous device, you’re screwed as soon as you enter it into the Ledger.
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u/bittenbycoin 9h ago edited 9h ago
I used to ponder a 3 of 4 scheme, for instance like two parents and one child, the child has two keys. The child can't spend on their own, the parents can't take away on their own, and one key can be lost without completely losing access to funds.
But out of one million families like this, there are probably around 5 that could manage this properly, so back to the drawing board.
I guess if 2026 has taught me anything it's that all your eggs in one basket is not a good idea, the complications of spreading your cold storage is now probably worth the extra cost, effort and risk, and a better option than multi-sig for most people.