You write a will that splits five bitcoin equally among your three children. You give the seed phrase to your eldest son for safekeeping. Three months later, you die in an accident. The eldest son uses the seed phrase to restore the wallet and transfers all five bitcoin to his own account. When the second son and youngest son ask for their share, he says: "Dad told me before he died that this was for me. As for your share, we will see."
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I have heard this story more than once. That is because crypto assets are different from bank accounts: whoever holds the private key owns the assets. A will that says "split equally" has no on-chain power at all. The first heir who gets the full seed phrase can empty the wallet in seconds.
To prevent this, the core rule is simple: Never let any single person hold a complete key that can withdraw all the assets.
Option 1: Use a multisig wallet for inheritance — the simplest and most direct way to prevent one heir from taking everything
[What to do]: Store assets in a multisig wallet, such as Mixin Safe's on-chain 2-of-3 non-custodial multisig, and set the signing threshold.
[How to do it]: Set up a 2-of-3 or 3-of-5 multisig wallet and give signing authority to different people. For example, you, your eldest son, and your second son each hold one key. While you are alive, any transfer needs your signature plus one son's signature. After you die, it needs at least two sons signing together to move funds.
[Completion standard]: Write in the inheritance list: "Assets are stored in a 2-of-3 multisig wallet. At least two people must sign together to transfer funds." The first heir cannot take the assets alone.
The advantage of this plan is that the execution rule is clear and verifiable on-chain. The downside is that if two heirs fall out, the assets may get stuck.
Option 2: Smart contract gradual release — so heirs never get the whole cake at once
[What to do]: Use a smart contract to release inherited assets in stages, so no heir receives everything in a single transaction.
[How to do it]: When configuring the inheritance contract, set the payment amount and interval. For example, configure 5 BTC to release 0.2 BTC per month for 25 months. You can also set the share and release schedule for several heirs, to make sure funds are not sent all at once to one person.
[Completion standard]: After the contract is deployed, confirm that the inheritance conditions are configured and the time lock is active. Even if one heir runs off with a single monthly release, the loss is only that month's amount, and the remaining funds still go to the others as planned.
Solutions like SmartWill use the idea of "small regular payments" to prevent an heir from spending or moving all funds at once. But note: once this kind of plan is deployed, it usually cannot be canceled or changed, so you need to think through the distribution strategy in advance.
Option 3: Shamir Secret Sharing + multiple verifiers — the ultimate way to split a seed phrase
[What to do]: Split the seed phrase into several parts using Shamir Secret Sharing, and set a rule that at least N parts are needed to rebuild the full seed phrase.
[How to do it]: Split the seed phrase into 5 parts and give them to 5 heirs. Set the rule that any 3 parts can recover the full seed phrase. This way, no single heir can do anything with only their own part. Even if 2 heirs work together, they are still 1 part short.
[Completion standard]: Each heir confirms that they only hold their own share, and you have clearly told them: "At least 3 people must come together to withdraw funds." This method has a mature implementation in patent literature: the owner gives fewer than the threshold of sub-keys to heirs, and gives the remaining sub-keys to verifiers such as a lawyer. The verifier only releases their share when certain conditions are met, such as a death certificate.
The advantage of this plan is security guaranteed at the cryptographic level. The downside is higher operational cost, and heirs need basic technical understanding.
Common cause of failure: treating "full authority" as "partial authority"
This is the easiest problem to overlook. You may think: "My eldest son knows technology best. I will let him withdraw first, then share with his siblings." That thought is reasonable, but once private key control is handed over, legal power has no on-chain effect. Without an on-chain mechanism such as multisig, time locks, or sharding, you rely only on the heir's honesty. In the face of a large amount of money, trust is fragile.
Risk reminder
All the plans above share one precondition: configure them while you are alive. If you leave it until after death and expect the executor to "find a way", you can only hope that the eldest son is a good person. Configuring these plans costs gas fees and time, but that is the hard cost of preventing the first heir from taking everything, and it cannot be skipped.
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How to verify after setup
After configuration, run a "step-by-step withdrawal test":
Simulate the scenario where the first heir gets the materials: Give your designated technical executor all the materials they are supposed to receive, such as one multisig key or one Shamir share.
Check whether they can withdraw alone: If they can withdraw all assets by themselves, the plan failed. You need to reduce the authority weight of a single heir. If they cannot withdraw alone, the plan is configured correctly.
Record the operating steps: Write the withdrawal process on paper, including who to contact to collect shares or signatures and who to contact to confirm inheritance conditions. Store this paper separately from the materials.
After the plan is set up, run a "stress test" every 12 months: contact at least one verifier and confirm that they still remember their duty, their contact information has not changed, and the materials they hold are still safely kept.
