Fireblocks Buyer’s Guide for Custodians & Sub-Custodians

Building a Custody Business Without Building Key Management

What a custodian actually sells is assurance, that client assets can only be moved by those authorized to move them. Every other capability, reporting, staking, settlement, client onboarding, rests on that.The technology underneath a custody business is not just another feature decision. Your clients will audit you on it, which makes it one of the most consequential choices you make.

Custody at institutional standards rests on the infrastructure beneath it. Fireblocks orchestrates the world’s financial systems, bridging traditional finance and digital assets so institutions can hold, move, manage and issue value on one platform. More than 2,500 enterprises run their digital asset operations on Fireblocks across 200+ blockchains, and the platform has secured over $16T in digital asset transactions. This guide is for trust companies, regulated custodians and sub-custodians building or re-platforming a digital asset custody offering.

For custodians, the decisions that carry the most weight are focused around three areas:

• Key control and recovery: Who can generate, hold and use key shares, and whether you can recover client assets without your technology provider’s participation
• Client asset segregation: How per-client holdings are structured, and what record proves segregation to a regulator or an administrator
• Evidence you can hand onward: Certifications, resilience documentation and audit output that satisfy your licence conditions and your clients’ due diligence

Comparison in this category is harder than in most, because the alternatives are not variations on one model. Licensing an HSM-based platform, appointing a third-party sub-custodian and building MPC infrastructure yourself produce different control profiles, different cost structures and different answers to the recovery question. The framework below is organised to make those differences clear before a build starts.

Where Fireblocks Excels in Digital Asset Infrastructure for Custodians and Sub-Custodians

The Control Questions Your Own Clients Will Ask You

Institutional allocators, funds and corporates now ask the same set of questions in operational reviews. Who generated the keys, where do the shares live, what is the quorum to sign, what happens if the technology provider fails, and how is my holding segregated from another client’s. Those questions have to be answerable in documentation, not in conversation.

Fireblocks is built so a custodian can answer them from the architecture rather than around it. Key shares are distributed across parties and devices under MPC-CMP, so there is no single location holding a complete key and no point at which the provider can move client assets. Recovery is designed to work independently, so a custodian is not operationally dependent on Fireblocks continuing to exist. Institutions that already run hardware-based key management can retain it through Fireblocks Key Link rather than replacing an approved and audited setup.

Fireblocks for Custodians and Sub-Custodians

• MPC-CMP key management distributes key shares so no single compromise, and no single party, can move client assets
• Independent recovery, so client assets remain recoverable without the participation of your technology provider
• Fireblocks Key Link integrates existing HSM and key management infrastructure, which preserves work your regulator has already reviewed
• Wallets-as-a-Service provisions segregated per-client wallets and account hierarchies at scale, which is the structural basis for both segregation and sub-custody
• Hot, warm and deep cold storage tiers in one system with automated sweeping, so movement between tiers is a rule rather than a ceremony
• Policy Engine enforces withdrawal limits, whitelists and approval quorums at the transaction layer, below application code, which is how you evidence controls rather than describe them
• Security Posture Management monitors configuration and access drift continuously, addressing a question that now appears in client due diligence
• Staking, Off Exchange and the DeFi security suite let you offer clients yield, trading collateral and onchain access without moving assets outside your control framework
• Tokenization for custody and administration of tokenized securities, funds and other onchain instruments
• Financial data produces reconciliation and reporting you can pass to clients, administrators and auditors
• Flexible deployment options where data residency, hosting or hybrid requirements apply
• The COR compliance package supports operational resilience obligations, including the third-party provider evidence DORA places on you

Digital Asset Use Cases for Custodians and Sub-Custodians

• Institutional custody with segregated per-client wallets and documented key control
• Retail custody at volume, where wallet provisioning has to be programmatic
• Sub-custody and delegated custody structures serving other regulated institutions
• White-labelled custody offered through a partner bank or platform
• Staking and yield services on assets held for clients
• Transaction settlement with counterparties and venues over the Fireblocks Network
• Custody and lifecycle administration of tokenized securities and funds
• Client reporting, reconciliation and audit support produced from platform records

Decision-Making Framework: Evaluating Digital Asset Infrastructure for Custodians and Sub-Custodians

Work through these categories with security, operations, compliance and legal together, and test each answer against the due diligence questionnaire your own clients will send you. A custodian serving a handful of institutional accounts and one provisioning retail wallets at volume will weigh them differently, but every row needs an answer that survives external review.

Category	What to Evaluate	Why It Matters for Custodians
Key generation and share distribution	How keys are generated, where shares reside, whether any single location holds a complete key, and whether the provider can sign	Key control is the foundation of custody and the core of your security model. Clients rely on your institution having full control over how keys are generated and used, with no provider in a position to sign or move their assets
Recovery independence	Whether client assets can be recovered without the provider’s participation, and whether that process is documented and testable	Provider concentration risk is a standing question from regulators. A recovery path that depends on your vendor surviving is not a recovery path
Existing key management reuse	Whether approved HSM or key management infrastructure can be retained rather than replaced	Re-approving a key management setup with a regulator is slow. Preserving reviewed infrastructure removes that from the critical path
Client asset segregation	Per-client wallet and account structures, omnibus versus segregated holdings, and the records that evidence it	Segregation is usually a licence condition. It has to be structural, not a reporting convention applied afterwards
Storage tiering and withdrawal controls	Hot, warm and cold tiers in one system, how movement between them is triggered, and where withdrawal policy is enforced	Transaction Authorization Policy (TAP) rules and automated sweeping govern how funds move between tiers and what can leave them. Limits, whitelists and approval quorums are enforced by the system, which removes the manual steps where operational error and insider risk concentrate
Signing performance at scale	Throughput, latency, and whether policy checks occur before signing	Client withdrawal expectations do not soften because your architecture is hardware-bound
Blockchain and asset coverage	Networks and tokens supported, effort to add a new chain, and whether additions are self-serve	Client demand determines your approved list
Sub-custody and white-label support	Account hierarchies for serving other institutions, and whether a partner can operate under your custody	Sub-custody is a distinct commercial model
Evidence you can pass onward	Certifications, resilience documentation, configuration monitoring, and reporting formats acceptable to auditors and administrators	You inherit your clients’ due diligence

Why Fireblocks: Core Value, Positioning & Differentiators for Custodians

Fireblocks is the technology layer beneath custody businesses rather than a custody service you resell. The distinction matters commercially and structurally. The custodian holds the client relationship, defines the policy framework and keeps the ability to recover assets independently. The key management architecture, certifications and resilience evidence are supplied and independently audited.

Core Capabilities

• MPC-CMP key management with distributed key shares and no single point of compromise
• Independent recovery, and Key Link for institutions retaining existing HSM infrastructure
• Wallets-as-a-Service for segregated per-client wallets and account hierarchies, with cold storage tiers under the same framework
• Policy Engine and automation for transaction governance, approval quorums and rules-driven storage tiering
• Security Posture Management for continuous configuration and access risk monitoring
• Staking, Off Exchange, Earn and the DeFi security suite for client-facing services on held assets
• Tokenization for custody and administration of onchain instruments
• Compliance tooling covering screening, Travel Rule and digital asset compliance, plus reconciliation and client reporting
• SOC 2 Type II, ISO 27001, ISO 27017, ISO 27018 and CCSS certifications, flexible deployment options, and publicly disclosed regulated entities
• A unified API with full developer documentation for integration into existing custody and core systems

Value Proposition

For a custodian, the platform does five things:

• Removes key management from your build scope without removing key control from your institution
• Makes segregation and approval quorums structural, so they can be evidenced rather than asserted
• Supplies the certifications and resilience documentation you pass on to clients and regulators
• Adds staking, trading collateral and onchain access as revenue without assets leaving your control framework
• Scales from institutional accounts to programmatic retail wallet provisioning on one system

How Fireblocks Measures Up for Custodians and Sub-Custodians

The table below compares Fireblocks against the three routes institutions most commonly look at when standing up a custody offering: licensing an HSM-based platform, appointing a third-party sub-custodian, and building MPC infrastructure in-house.

Capability	Fireblocks	HSM-Based Custody Platform	Third-Party Sub-Custodian	In-House Build
Who can move client assets	Only your institution, via distributed key shares	Your institution, keys in vendor hardware	The sub-custodian	Your institution, self-managed
Key generation and share distribution	MPC-CMP, shares across parties and devices	Generated and held in hardware, single location	Not your process	Engineering burden
Recovery without the provider	Yes, independent recovery	Hardware and vendor dependent	Not applicable, assets are not yours to recover	Self-managed
Reuse of existing HSM infrastructure	Yes, via Key Link	Native to the model	Not applicable	Self-managed
Client asset segregation	Per-client wallets and account hierarchies	Achievable, manual configuration	Frequently omnibus	Must build from scratch
Storage tiering and withdrawal controls	Hot, warm and cold with automated sweeping	Cold-focused, manual movement	Sub-custodian defined	Custom build required
Signing performance at scale	High throughput, policy checked before signing	Slower, hardware bound	Sub-custodian service levels	Depends on the build
Blockchain and asset coverage	200+ networks, self-serve token additions	Limited, per-chain firmware work	Sub-custodian approved list	Limited by dev capacity
Sub-custody and white-label structures	Supported through account hierarchies	Achievable, heavy configuration	You are the client, not the provider	Must build from scratch
Client-facing staking and onchain access	Yes, under your policy controls	Rarely supported	Rarely permitted	Custom build required
Evidence you can pass to clients	SOC 2 Type II, ISO certifications, COR package	Hardware certifications only	The sub-custodian’s evidence	Self-certified
Deployment flexibility	Cloud, hybrid or data residency options	On-premise typical	Not applicable	Self-hosted

An HSM-based platform is well understood by security teams and auditors, and for an institution with deep cold storage requirements and modest transaction volume it remains a coherent choice, with per-chain work and manual movement as the cost. Appointing a sub-custodian is the fastest path to a live offering and the appropriate one where custody is not intended to become a core competency, at the price of holding neither the keys nor the client control. Custodians taking this route can appoint Fireblocks Trust Company as their sub-custodian. Building MPC infrastructure keeps everything and commits a specialist team indefinitely, and the part that proves hardest is not the cryptography but the certification and resilience evidence your clients will ask you to produce.

How Custodians Launch and Scale Services With Fireblocks

Bakkt enhanced its custody offering on Fireblocks infrastructure. Sygnum Bank uses Fireblocks Off Exchange to give institutional clients custody assurance while they trade, which is the adjacent-revenue pattern in practice. Boerse Stuttgart Digital powers regulated institutional digital asset access for a European exchange group, and ABN AMRO tokenized, issued and held digital securities as a major bank operating inside existing risk and reporting structures.

The sub-custody and delegated models follow the same architecture. Zerocap moved from a prefunded exchange model to off-exchange custody at institutional scale, and institutions serving other institutions build on the same account hierarchies that make per-client segregation structural.

From Evaluation to Implementation for Custodians

Implementation is structured around the reviews a custody business has to pass, with professional services for architecture, migration and key ceremony work, and Global Platinum Support for operations that carry client obligations.

Sandbox Environment and Developer Tools

Simulate custody operations in the Fireblocks sandbox, complete with API users, transaction policies and prefunded wallets. Test account hierarchies, approval quorums, storage tiering and the client reporting output before any client asset is involved.

Join the Sandbox

See a Live Demo

Connect with the team to walk key architecture, recovery design, segregation structures and the evidence pack against your licence conditions and client due diligence requirements.