[bitcoindev] Re: BIP idea: Timelock-Recovery storage format

'Oren' via Bitcoin Development Mailing List
2026-01-01T16:22:48Z

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Hi AdamSZ, list,
Thanks for showing interest in the BIP and happy new year.

> Btw, do you think you should address directly the philosophy found in
Liana, and what setups they have decided to expose? (i.e. what's the delta,
here).
Yes, I think it's a good idea to talk about the advantages and
disadvantages of pre-signed transactions vs script-based wallets. I'll add
it to the Motivation section.

> Should the BIP actually be something with more flexibility in transaction
structure, so as to cover more use-cases?
I think it's good to limit the structure of the transactions, so that
different services could easily integrate this feature.
One guy that I talked to suggested building a more sophisticated sequence
of transactions with multiple wallets, for example that after 90 days the
Bitcoin will move to his wife's wallet, from which there will be another
pre-signed transaction that moves the Bitcoin to his brother's wallet after
180 days, etc.
But after all, trying to support all custom logics and use-cases will end
up in a service that compiles general-purpose "code" instead of something
useful for standard users.

> Is there a case for requesting a feature in Core that one could do a
'testmempoolaccept' with a conditional setting of the time/block height as
argument?
I've asked for a testmempoolaccept RPC that ignores nSequence/nLocktime
here: https://github.com/bitcoin/bitcoin/issues/32142
It's a problem even in transactions with a single nLocktime.
testmempoolaccept breaks on the first problem that it finds. Suppose you
are signing a transaction with a future nLocktime, and testmempoolaccept
breaks on "non-final" - how do you know that there are no other problems in
the transaction? How can you tell that the cryptographic signatures are
good, and what if it's a script-based wallet?
Some worry that complicate the testmempoolaccept RPC diverge from how
transactions are checked in sendrawtransaction, and I somewhat agree with
that.
Checking the signatures of P2WPKH wallets is straight-forward, but in order
to build a service that verifies the Recovery transaction of a complicated
wallet (i.e. multisig, taproot, etc.), without initiating the plan - I
guess you would need to run a node with patched code for testmempoolaccept.

> I'm probably being an idiot, but: since you're defining alert_inputs as
just txid:vout, what's the point of including it since that data is already
in alert_tx, no?
I did mention that the JSON has some information duplicated. Even the
alert_txid can be calculated from the raw transaction.
This is useful for displaying the information to the user for review. For
example, a webpage to which you drag-n-drop the JSON file, shows you its
information and has a button saying "Upload for Monitoring".
This will allow the frontend to show the user the list of UTXOs covered by
the recovery-plan, without complicated frontend-code to parse the raw
transaction.
Of course, if the user clicks "Upload for Monitoring" and the backend finds
out that the alert_inputs mismatch the raw transaction, the whole process
should be rejected with a warning that the file was corrupt (possibly
maliciously).

> One last thing, that 388 day limit is a little unfortunate, no? I
certainly think a year is a good, reasonable "long time", but still, all
the same.
388 days is just the maximal value that you get from BIP-68:
After setting the correct bit flags, the relative-locktime is calculated
from the lowest 16 bits, in units of 512 seconds.
This gives a maximal value of (2^16 - 1) * 512 seconds = 33,553,920 seconds
= 388 days, 8 hours and 32 minutes.
Users can obviously choose a shorter cancellation-window.

Regards,
Oren

On Thursday, January 1, 2026 at 4:34:07 PM UTC+2 waxwing/ AdamISZ wrote:

> Hi Oren, list,
>
> I do think this is a really good general idea - and certainly fits into
> "this could be a BIP". Current covenant-less "deadman's switch" style
> systems are of course limited, but useful, at least to the enthusiast that
> can hand-craft them. Avoiding the "need to refresh every interval" is
> clearly desirable, though the extra complexity *may* end up being more
> trouble than it's worth (clearly, you don't think so!).
>
> Btw, do you think you should address directly the philosophy found in
> Liana, and what setups they have decided to expose? (i.e. what's the delta,
> here).
> Should the BIP actually be something with more flexibility in transaction
> structure, so as to cover more use-cases?
>
> Other comments stimulated by the BIP text:
>
> "The testmempoolaccept RPC can receive a list of transactions in which the
> later transactions may depend on earlier transactions - however in our case
> the Recovery Transaction has an nSequence relative-locktime, and therefore
> calling testmempoolaccept 'alert-tx' 'recovery-tx' will fail, claiming that
> the Alert Transaction UTXO is not confirmed (and the required time window
> has not passed). "
>
> This sounds like a pretty chunky and important problem (which surprised
> me, as in, it never occurred to me). Speaking for myself, I would not rest
> easy with a recovery plan that I couldn't unambiguously check as follows:
> "I really, really want to know that this recovery works, but much more than
> that, I *must* know that it doesn't work (leak my funds) before the
> intended deadline".
>
> With a single nlocktime you can do that (testmempoolaccept -> "non-final").
>
> Is there a case for requesting a feature in Core that one could do a
> 'testmempoolaccept' with a conditional setting of the time/block height as
> argument? Would that solve this issue? I'm guessing not, as (clue is in the
> name!) the tool was mostly designed around "how does this tx interact with
> the currently seen mempool" more than "forget conflicts, is this even
> valid/could it ever be valid in and of itself?" (yeah perhaps it's just an
> incoherent question..?).
>
> "alert_inputs (mandatory): An array of up to 10,000 inputs spent by the
> Alert Transaction. Each input is a string in the format "txid:vout" where
> txid is a 64-character lowercase hexadecimal string and vout is a decimal
> number of up to 6 digits.
> alert_tx (mandatory): The raw Alert Transaction in uppercase hexadecimal
> format. A string of up to 800,000 characters."
>
> I'm probably being an idiot, but: since you're defining alert_inputs as
> just txid:vout, what's the point of including it since that data is already
> in alert_tx, no?
>
> One last thing, that 388 day limit is a little unfortunate, no? I
> certainly think a year is a good, reasonable "long time", but still, all
> the same.
>
> Cheers,
> AdamISZ/waxwing
>
> On Sunday, December 28, 2025 at 11:59:43 AM UTC-3 Oren wrote:
>
>> Reposting here from BitcoinTalk
>> <https://bitcointalk.org/index.php?topic=5569543.0>:
>>
>> After a short talk with Ava Chow during BTC++ Taiwan, I'm starting this
>> thread to discuss whether my idea is BIP-worthy.
>>
>> Motivation for Timelock-Recovery plans:
>> Storing seeds for recovery & inheritance is scary.
>> Pre-signed transactions to a secondary-wallet/custodian, are safer to
>> handle and backup due to their immutability.
>> A single pre-signed transaction with a future nLocktime requires
>> "renewal" when the nLocktime deadline is getting close, which could be
>> annoying (i.e. if the seed is split over multiple geographic locations).
>> Covenants/Vaults are still being debated, and could scare less-technical
>> Bitcoiners.
>>
>> Solution:
>> Pre-signing a pair of transactions:
>> • Alert/Initiate Transaction: A consolidation transaction that keeps
>> most funds on the original wallet (except for a minimal amount that goes to
>> anchor-addresses, for CPFP acceleration)
>> • Recovery Transaction: A transaction that moves the Bitcoin from the
>> consolidated UTXO to the secondary-wallet(s), with an nSequence
>> relative-locktime that gives the user enough time to move the funds
>> elsewhere (assuming they noticed that the Alert transaction was mined, and
>> still have the seed or signed an alternative transaction in advance).
>>
>> Similar to a single pre-signed transaction with a future nLocktime,
>> Timelock-Recovery plans will not include new funds that are added to the
>> wallet, and will be revoked even if a tiny amount is spent. This mechanism
>> is intended for wallets that are going to remain untouched for a long time.
>>
>> An example implementation can be found in the Timelock Recovery plugin
>> that I've implemented for Electrum <https://electrum.org> (merged since
>> Electrum v4.6.0b1). Details and demo videos can be found at:
>> https://timelockrecovery.com.
>> The plugin creates a UI for signing the two transactions, then saving
>> them either in a PDF file (with detailed manual instructions for
>> less-technological Bitcoiners how to broadcast them), or in a *JSON
>> format*.
>>
>> The BIP will be about the JSON format, which includes not only the raw
>> transactions themselves, but also user-information (i.e. name, description,
>> destination-labels, wallet-name, wallet-version), and data about the
>> transactions (i.e. txids, amounts, fees, input-utxos, anchor-addresses,
>> relative-locktime).
>> A standard JSON format will allow implementing a compatible feature on
>> other wallets, as well as apps/servers for monitoring & initiating
>> timelock-recovery plans - such as the one being developed by RITREK.com
>> <https://ritrek.com> (disclosure: I'm one of RITREK's founders).
>>
>> Let me know what you think!
>>
>> Oren
>>
>>

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