CHAIN-OF-CUSTODY

Chain-of-Custody: What Must Be Captured (Per Object)

Definitions:
The object key
identifies the name and location (path) of an object.
The object instance identifier
uniquely identifies a particular version of an object created by a write operation.

In the context of TG, Chain-of-Custody is a single, verifiable record that starts with authorization, follows execution across cloud boundaries, and ends with integrity verification and attestation. It establishes the specific control and handling of a single object instance from ingest to destination.

The "chain-of-custody" for an object is defined by these seven mandatory pillars:

  1. 1
    Authorization (Standing Permissions Reference)
    PERMISSIONS

    Instead of a per-transfer approval, the record references the pre-granted cloud permissions under which the transfer was executed.

    • Source Identity: The specific AWS IAM Role, GCP Service Account, or Azure identity used.
    • KMS Access: The specific encryption keys accessible to TG for that operation.
    • Verification: A timestamp of when these permissions were last verified to be valid.
  2. 2
    Source Object Identity
    INGEST

    TG identifies the "ingest" state by capturing the precise instance of the object, not just its name.

    • Instance Identifiers: Capture CSP-specific version markers (e.g., AWS versionId, GCP generation, or Azure ETag).
    • Source Checksum: The plaintext hash of the object before any transit encryption is applied.
  3. 3
    Execution Linkage
    LINKAGE

    This connects the static object identity to the active transfer process.

    • CSP Operation IDs: Captures internal chunk or batch operation IDs from the cloud provider.
    • Resiliency Events: Logs retry or resume events, including attempt counts and byte offsets.
  4. 4
    Destination Object Identity
    LANDED

    Upon completion, TG records the "landed" state of the object.

    • New Instance Identifier: Captures the generation or version ID created by the write operation at the destination.
    • Reassembly Verification: The destination plaintext checksum is calculated after decryption and chunk reassembly.
  5. 5
    Integrity Verification
    TRIPLE-LOCK

    A definitive record of the "Triple-Lock" hash comparison:

    • Algorithm: Explicitly records the hash algorithm used (e.g., SHA-256).
    • Comparison: Lists the source vs. destination checksums and the explicit "Match" or "Fail" result.
  6. 6
    Outcome & Supersession
    VERSIONING

    This addresses your "Semantic Versioning" policy for same-named objects.

    • Collision Handling: If an overwrite occurred at the operational path, the record must include a reference to the prior destination object instance and a timestamp of the supersession.
  7. 7
    Attestation
    SIGNED

    The final terminal state of the chain-of-custody is the Signed Transfer Manifest.

    • Cryptographic Binding: The signature covers all the data points above, asserting the completeness and finality of the entire record.