Bitcoin Signers Unreachable After Time as Availability Decay

Signer Availability Decay in Multisig Arrangements

This memo is published by CustodyStress, an independent Bitcoin custody stress test that produces reference documents for individuals, families, and professionals.

Multi-Signature Structures and Their Dependencies

Multi-signature custody requires multiple parties to authorize transactions. At setup, those parties agreed to participate and were reachable. Time passes. Circumstances change. The scenario where bitcoin signers unreachable after time becomes relevant when the holder needs signatures and discovers that people who once participated can no longer be found or will no longer cooperate.

What follows covers how signer availability decays over time. Relationships that seemed stable shift. Contact information becomes outdated. People move, die, or simply disengage. The multi-signature structure that provided security at setup becomes a barrier when required signers are no longer available.

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Multi-Signature Structures and Their Dependencies

Multi-signature arrangements require a threshold of signers to approve transactions. A two-of-three setup needs two people from a group of three. A three-of-five needs three from five. The threshold provides security because no single point of compromise can steal funds.

This security depends on enough signers being available when needed. Losing one signer in a two-of-three arrangement still allows transactions. Losing two signers makes the funds inaccessible regardless of how legitimate the remaining holder's need might be.

Signers hold keys, but they also hold obligations. When they agreed to participate, they implicitly agreed to be available for signing when requested. That implicit agreement has no enforcement mechanism. Life circumstances may override the original commitment.

Geographic distribution often accompanies multi-signature setups. Signers may be spread across different locations for security reasons. That same distribution makes coordination harder as signers' lives diverge and contact becomes less routine.

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Relationship Changes Over Time

Personal relationships evolve. Close friends drift apart. Family members become estranged. Business partners dissolve their ventures and lose contact. The people chosen as co-signers based on current relationships may become strangers over years.

Conflict can poison previously cooperative relationships. A falling out with a co-signer creates not just absence but active resistance. The former friend who helped set up multi-signature custody may refuse to sign out of spite, turning security into hostage-taking.

Life priorities shift as people age. A co-signer who was enthusiastic about bitcoin at thirty may have lost interest at fifty. Their keys sit unused in forgotten storage. Asking them to locate and use those keys may seem like an unreasonable imposition from their current perspective.

Death removes signers permanently. A co-signer who dies leaves behind keys that may or may not be accessible to their estate. The primary holder now depends on the deceased's heirs finding and being willing to use keys they may not understand.

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Contact Information Decay

Reaching someone requires knowing how to contact them. Phone numbers change. Email addresses are abandoned. Physical addresses become outdated as people move. The contact information recorded at setup may be useless years later.

Professional relationships often provide contact paths. If co-signers worked together, workplace directories helped locate them. When professional ties end, those paths close. Former colleagues become surprisingly hard to find when neither works at the same place.

Social media offers apparent contact options but unreliable response. A message sent to an old account may never be seen. Privacy settings may block communications from people outside approved networks. The visible presence of someone online does not mean they can actually be reached.

Intermediary contacts also decay. Someone who knew how to reach the co-signer may themselves become unreachable. Chains of contact that once connected people break at any link. The longer time passes, the more links break.

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Technical Capability Decay

Co-signers who understood the signing process at setup may lose that understanding over time. Software changes. Procedures become unfamiliar. The technical capability to participate in signing degrades even when willingness remains.

Hardware holding keys requires maintenance. A co-signer's hardware wallet needs firmware updates, battery replacement, or eventual device replacement. Without active attention, the hardware may fail or become incompatible with current software.

Passwords and PINs protecting signing keys face the same memory decay as passphrases. A co-signer who set a PIN three years ago may not remember it today. Their willingness to sign means nothing if they cannot access their own key.

Backup seed phrases for co-signers' keys face similar risks. If the hardware fails and the co-signer must recover from backup, they need to have maintained those backups. Years of inattention may have rendered their backup useless through loss, damage, or forgetting where it was stored.

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When Unreachability Becomes Critical

Routine transactions reveal unreachability early. If the holder regularly needs signatures, they discover problems while options remain. A co-signer who fails to respond to one request can be replaced before the situation becomes dire.

Infrequent access delays discovery. If the holder goes years without needing to move funds, co-signer availability is untested. The first attempt after a long gap may reveal multiple unreachable signers simultaneously, with no time to have addressed each problem individually.

Emergency situations create the worst conditions for discovering unreachability. Medical emergencies, legal deadlines, or urgent financial needs demand fast action. Learning that signers are unreachable during an emergency means facing the emergency without access to resources that exist but cannot be reached.

Estate situations concentrate risk. The primary holder's death is exactly when signatures are needed and when the relationship that motivated co-signers' participation no longer exists. Heirs contacting co-signers are strangers asking favors, not friends requesting help.

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The Reluctance Problem

Even reachable signers may be reluctant to participate. Their agreement to help was made years ago under different circumstances. Asking them to follow through now may encounter resistance they did not anticipate feeling.

Inconvenience creates friction. Locating keys, updating software, and coordinating timing all take effort. A co-signer with a busy life may delay indefinitely, treating signing requests as low priority items that never reach the top of their list.

Liability concerns emerge over time. A co-signer who hears that bitcoin has regulatory complications may worry about their role. Even without real legal risk, perceived risk can make someone unwilling to participate in what seems like potential trouble.

Relationship dynamics change how requests are received. A co-signer who feels the relationship has been one-sided may view signing requests as impositions. Past grievances unrelated to bitcoin custody may surface as reasons to refuse or delay.

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Partial Availability Scenarios

Sometimes some signers are available but not enough. A three-of-five arrangement where only two signers can be reached remains locked despite partial cooperation. Near-sufficiency provides no access.

Partial availability creates awkward dependence on the missing signers. The holder must make extraordinary efforts to locate or persuade one more person while available signers wait. The process stalls at the threshold gap.

Available signers may lose patience. If efforts to find additional signers drag on, those who responded promptly may become frustrated. Their availability is time-limited. Delay in reaching the threshold may result in initially available signers becoming unavailable as well.

Negotiations may emerge. A reluctant signer who realizes their signature is necessary may seek compensation or concessions. The multi-signature structure that prevented theft enables a form of extortion when one party can block access unilaterally.

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Replacement Challenges

Replacing an unavailable signer requires access that the unavailability itself prevents. Moving funds to a new multi-signature arrangement with different signers requires the old arrangement's threshold. If that threshold cannot be met, replacement is impossible.

Advance key rotation avoids this trap but requires regular attention. Periodically moving funds to updated arrangements with current signers maintains accessibility. This maintenance requires discipline that holders may not maintain over years.

The holder who waits until signers are unreachable to consider replacement has waited too long. By definition, the unreachability prevents the very transactions that would enable working around it. The problem cannot be solved once it has fully manifested.

Social pressure to maintain original arrangements works against rotation. Co-signers may feel offended at being replaced. The holder may feel awkward asking new people while old ones are technically still available. These social frictions discourage the maintenance that would prevent availability decay from becoming critical.

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Assessment

Bitcoin signers unreachable after time represents availability decay in multi-signature custody. Relationships change, contact information becomes outdated, and technical capability degrades. Co-signers who participated readily at setup may be unfindable or unwilling years later.

Infrequent access delays discovery of unreachability until moments of need. Emergency and estate situations create the worst conditions for discovering that required signers cannot be reached. Even reachable signers may be reluctant to participate due to inconvenience, liability concerns, or relationship friction.

Partial availability below the required threshold provides no access. Replacing unavailable signers requires the very access that their unavailability prevents. The multi-signature security that protects against theft also creates dependence on signer availability that decays over time without active maintenance.

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System Context

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Bitcoin Multiple Signers Coordination

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