Decaying Multisig

Description

Decaying multisig is a custody technique where the number of keys required to move the funds decreases over time. For example, a 3 of 3 multisig may decay to only need 2 of the 3 keys after 1 year, and then to 1 of the 3 keys after 5 years.

One use case for this is mitigating against loss of funds due to key loss. If a key is lost, the owner only needs to wait until the next decay step to recover the funds. Another use case is for loosening consensus for co-managed assets. For example, a board of directors may generally require a higher threshold (67%) to spend funds, but decrease that over time (to 51%) to avoid allowing a subset of signers to deadlock the funds.

Vault Configuration Example

All 3 signers are needed to spend. After 10,000 blocks, the after block meets one of the threshold's conditions, so only 2 signatures are needed to unlock the funds. Finally, after 20,000 blocks, 2 conditions are met by the after statements and only 1 additional signature is needed.

Inputs

Threshold
List of Signers (extended descriptor)
List of Lock times (integers)

Miniscript

thresh(
    <threshold>,
    pk(Key1),
    pk(Key2),
    pk(Key3),
    ...
    after(Timelock1),
    after(Timelock2),
    ...
)

Output Descriptor

tr(InternalKey,thresh(3,pk(Key1),s:pk(Key2),s:pk(Key3),snl:after(Timelock1),snl:after(Timelock2)))

Example

Example Output Descriptor

tr(3ec243044db203bc418092014b46bfe9494a1c16ee66160e385d7dd676e378cd,thresh(3,pk([7356e457/86'/1'/784923']tpubDCvLwbJPseNux9EtPbrbA2tgDayzptK4HNkky14Cw6msjHuqyZCE88miedZD86TZUb29Rof3sgtREU4wtzofte7QDSWDiw8ZU6ZYHmAxY9d/0/*),s:pk([4eb5d5a1/86'/1'/784923']tpubDCLskGdzStPPo1auRQygJUfbmLMwujWr7fmekdUMD7gqSpwEcRso4CfiP5GkRqfXFYkfqTujyvuehb7inymMhBJFdbJqFyHsHVRuwLKCSe9/0/*),s:pk([f3ab64d8/86'/1'/784923']tpubDCh4uyVDVretfgTNkazUarV9ESTh7DJy8yvMSuWn5PQFbTDEsJwHGSBvTrNF92kw3x5ZLFXw91gN5LYtuSCbr1Vo6mzQmD49sF2vGpReZp2/0/*),snl:after(1721743844),snl:after(1747663844)))#p0skyz4j

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