¶ 901
Overview
Scope of the chapter. A person who owns a digital asset holds it through some arrangement for the custody of the key material that permits the asset to be transferred. That arrangement may be as simple as a phrase written on paper and kept in a drawer, or as elaborate as a regulated trust company holding the asset in an offline vault under a written agreement, with sub-custodians, insurers and auditors behind it. This chapter compares the principal custody models as legal arrangements. For each model it asks who has control of the asset in law and in fact, where the single points of failure lie, and what happens to the asset when a participant dies, becomes incapacitated or becomes insolvent. It also asks how the parties allocate the risk of loss. The chapter closes with guidance on choosing a model for different kinds of client and a checklist for documenting the choice.
Why the model matters. The legal consequences of holding a digital asset turn to an unusual degree on the custody arrangement. The same quantity of bitcoin may be the holder's property, a contract claim against an exchange, a beneficial interest under a trust or bailment, or a share in a pool that a court will distribute pro rata among unsecured creditors. Which of these it is depends on the terms of the arrangement and on how the custodian performs them. The bankruptcy decisions discussed in this chapter show the range. In one case, assets that customers had placed in a segregated custody program were held to be the customers' property, while assets the same customers had placed in a yield program on different terms were held to belong to the company. In another, assets that a regulated trust company had received from customers were held to be property of its estate because the company had swept them into pooled wallets and could no longer trace them. See infra ¶¶ 960.04, 960.06.
The two questions in every model. Every custody model answers two questions, and the practitioner should keep them separate. The first is technical and operational: what key material exists, where it is stored, who can use it, and what must happen before a transaction can be signed. Chapter 2 explains the technology. See supra ¶¶ 230–250. The second is legal: what rights each participant has in the asset and against the others, and the treatment of those rights by property law, by Article 12 of the Uniform Commercial Code, by regulators and by a court in insolvency. A model that is secure in the first sense may leave the owner exposed in the second, and the reverse. An exchange that keeps customer assets in well-run offline storage may still hold them on terms that make the customer an unsecured creditor. A holder who keeps a single key in a safe may have complete legal ownership and no protection against loss.
Vocabulary. The chapter uses the terms defined in Chapter 1. See supra ¶ 180. Key material means private keys, seed phrases and key shares. Self-custody means an arrangement under which the owner alone holds all key material needed to transfer the asset. Shared control means an arrangement under which two or more persons must cooperate to sign, whether by an on-chain multi-signature script or by a threshold-signature scheme that produces a single signature from shares. Collaborative custody means a shared-control arrangement in which the owner holds some key material and one or more service providers hold the rest. Third-party custody means an arrangement under which a custodian holds all the key material needed to transfer the asset for the owner's account. Exchange custody is third-party custody provided by a trading platform as part of its trading service.
Relation to other chapters. This chapter is concerned with the structure of custody arrangements and the risks each structure carries. The legal characterization of the relationship between a customer and a custodian, as bailment, trust or debt, is examined in Chapter 10. The regulatory status of custodians, including the qualified-custodian requirement for investment advisers and the state trust charters, is examined in Chapter 11. Staking, lending and rehypothecation of custodied assets are examined in Chapter 12. Control under U.C.C. § 12-105, and the effect of shared power on control, are examined in Chapter 6. See supra ¶¶ 630.08–630.12. The duties of trustees who hold digital assets are examined in Chapters 14 to 16, key succession on death in Chapter 22, and the treatment of customer assets in a custodian's bankruptcy in Chapters 27 and 28.
Organization. Section 910 frames custody as a legal question. Sections 920 to 960 take the models in turn: self-custody with a single key (¶ 920), shared control by multi-signature and threshold schemes (¶ 930), collaborative custody and key-holding agents (¶ 940), qualified third-party custody (¶ 950) and exchange custody, with the record of exchange and custodian failures (¶ 960). Section 970 addresses the allocation of loss, insurance, assurance reports and proof of reserves. Section 980 addresses the choice of a model for individuals, trusts, funds and operating companies, and recovery arrangements. Section 990 collects drafting points and a checklist.