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This comprehensive explanation has been generated from 33 GitHub source documents. All source documents are searchable here.
Last updated: October 7, 2025
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For authoritative documentation, please consult the official GLEIF vLEI trainings and the ToIP Glossary.
Chain-of-custody is the chronological documentation of the sequence of custody, control, transfer, analysis, and disposition of materials or data, providing verifiable provenance through cryptographically-linked records that establish authenticity and integrity from origin to current state.
Chain-of-custody represents the documented chronology of ownership, control, transfer, and handling of physical materials or digital data. In traditional contexts, it serves as a paper trail establishing the complete history of an object from its origin through all subsequent custodians. In digital identity systems, chain-of-custody extends to cryptographically verifiable records that prove the authentic provenance of data, credentials, and authorizations.
The core properties of chain-of-custody include:
The scope encompasses both physical custody (who possessed materials) and logical custody (who had authority over data or identifiers), with particular emphasis on maintaining unbroken documentation that can withstand scrutiny in legal, regulatory, or trust-establishment contexts.
Chain-of-custody originated in legal and forensic contexts where establishing the integrity of evidence was paramount. In criminal proceedings, any gap in the custody record could render evidence inadmissible. The concept expanded to:
Traditional chain-of-custody relied on , , and to maintain records. This created vulnerabilities:
Implementing chain-of-custody verification requires:
When constructing custody chains:
The emergence of portable technology enabling on-site analysis shortened physical custody chains, but digital systems introduced new challenges around data provenance, authenticity, and verifiable attribution.
KERI transforms chain-of-custody from a documentation problem into a cryptographic verification problem. Rather than relying on trusted intermediaries to maintain custody records, KERI provides self-certifying, cryptographically verifiable provenance chains through several integrated mechanisms:
The KEL serves as an append-only, cryptographically-chained custody record for identifier control. Each establishment event (inception or rotation) represents a custody transfer of control authority:
The KEL's backward and forward chaining through cryptographic digests creates a tamper-evident chain where any modification to historical events is immediately detectable. The pre-rotation mechanism provides cryptographic commitment to future custody transfers before they occur, preventing unauthorized custody seizure.
ACDCs extend chain-of-custody from identifier control to data provenance. Each ACDC forms a node in a directed acyclic graph (DAG) where edges represent custody relationships:
Proof-of-Authorship Chains: ACDCs provide granular provenanced proof-of-authorship through cryptographically-linked chains. The SAID (Self-Addressing Identifier) of each ACDC creates a content-addressable commitment that binds the data to its creator.
Proof-of-Authority Chains: Beyond authorship, ACDCs support delegated authorization chains where custody of authority (not just data) is tracked. The edge section enables three operators:
These operators enable flexible custody models while maintaining cryptographic verifiability of the complete chain.
The TEL provides registry-backed chain-of-custody for credential lifecycle events:
TELs are anchored to KELs through seals, creating a two-layer custody architecture where the KEL establishes control authority and the TEL tracks credential custody.
KERI's witness infrastructure provides distributed custody verification. Witnesses maintain independent copies of KELs and provide receipts that establish first-seen consensus. This creates:
The KAACE (KERI's Agreement Algorithm for Control Establishment) ensures witnesses reach consensus on custody events without requiring blockchain-style total ordering.
KERI supports privacy-preserving chain-of-custody through:
Graduated disclosure: Custody information can be revealed progressively:
Chain-link confidentiality: Custody obligations flow through the disclosure chain, binding all downstream recipients to confidentiality requirements. This creates contractually-protected custody chains where legal obligations are cryptographically linked to data custody.
KERI's chain-of-custody differs fundamentally from traditional systems:
| Traditional | KERI |
|---|---|
| Paper documentation | Cryptographic verification |
| Trusted intermediaries | Self-certifying identifiers |
| Centralized records | Distributed KELs/TELs |
| Post-hoc verification | Real-time verification |
| Gap-prone | Cryptographically continuous |
| Jurisdiction-dependent | Globally verifiable |
The key innovation is eliminating trust in intermediaries while maintaining (and exceeding) the verifiability guarantees of traditional custody systems.
Supply Chain Provenance: KERI enables authentic data supply chains where physical supply chains have digital twins tracked through ACDC chains. Each custody transfer in the physical world is anchored to a cryptographically verifiable event in the digital twin, enabling:
Credential Delegation Chains: The vLEI ecosystem demonstrates hierarchical custody:
Each level maintains cryptographic proof of custody authorization through the complete chain back to GLEIF.
Data Transformation Pipelines: Decentralized Autonomic Data (DAD) items enable verifiable data flow chains where each transformation step is cryptographically documented. This supports:
Digital Rights Management: ACDCs can track custody of authority over digital assets, enabling verifiable transfer of rights without centralized registries.
End-to-End Verifiability: Any party can independently verify the complete custody chain without relying on trusted intermediaries. The end-verifiable property means verification requires only the KEL/ACDC chain itself.
Ambient Duplicity Detection: Attempts to create conflicting custody records are automatically detected through duplicity detection mechanisms, providing ambient verifiability where anyone, anywhere, anytime can detect custody fraud.
Scalable Verification: Unlike blockchain systems requiring global consensus, KERI's custody verification scales horizontally through witness pools and watcher networks without performance degradation.
Privacy Preservation: Graduated disclosure enables selective custody revelation where parties can prove custody without revealing sensitive details about the custodied data.
Legal Compatibility: Chain-link confidentiality creates legally-binding custody obligations that flow through the chain, making KERI custody records admissible in legal proceedings.
Complexity: Implementing cryptographic custody chains requires understanding KELs, ACDCs, TELs, witnesses, and their interactions. This is more complex than simple database records.
Key Management: Custody is tied to cryptographic keys. Key compromise can break the custody chain, though KERI's pre-rotation and rotation mechanisms provide recovery paths.
Witness Dependency: Custody verification relies on witness availability. While watchers provide redundancy, complete witness failure could impact custody verification (though not custody itself, which is self-certifying).
Storage Requirements: Maintaining complete custody chains requires storing full KELs and ACDC graphs. For long-lived identifiers with many events, this can be substantial.
Temporal Considerations: Custody chains are temporally ordered, but KERI uses first-seen rather than absolute timestamps. This provides stronger security but may complicate integration with systems requiring precise timestamps.
Despite these trade-offs, KERI's cryptographic chain-of-custody provides provably stronger guarantees than traditional systems while enabling decentralized, scalable verification impossible with paper-based or centrally-managed custody records.