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BRC-115: Identity-Linked Deterministic Token Verification Framework

Author:
Jake Jones (jake.jones@bsvassociation.org)

Status: Draft
Version: 1.0

Required Dependencies:

  • BRC-0042 (Deterministic Key Derivation)
  • BRC-0092 (Mandala Token Protocol)
  • BRC-0107 (Commitment-Based Token Integrity)
  • BRC-0108 (Identity-Linked Token Metadata)

Optional Dependencies:

  • BRC-0043 (Purpose Identifiers)
  • BRC-0067 (SPV Packaging Format)

Abstract

BRC-115 defines a deterministic, SPV-verifiable framework for identity-linked token transfers on Bitcoin SV. It specifies how wallets verify compliance requirements using BRC-0042 key derivation, BRC-0107 commitments, and BRC-0108 identity bindings — without relying on overlay networks or external validators.

This standard ensures identity-restricted token transfers remain interoperable, decentralized, portable, and enforceable while enabling selective privacy, regulatory compliance, and recovery options within the original peer-to-peer Bitcoin model.

Motivation

Existing BSV token standards provide token encoding (BRC-0092), verifiable state transitions (BRC-0107), and identity metadata (BRC-0108). However, none define:

  • How identity-based constraints are enforced
  • How signatures bind identities to transaction lineage
  • How SPV wallets validate compliance without a trusted intermediary
  • How field-level revelation is performed and verified consistently

BRC-115 introduces a unifying rule set that makes identity-restricted token usage deterministic, verifiable, and portable between software implementations.

Architecture Overview

flowchart TB

    Wallet["Wallet / Client Logic"]
    Core["Protocol Enforcement Layer"]
    Ledger["SPV Proof / Bitcoin Ledger"]

    Wallet -->|Enforces BRC-115| Core
    Core --> Ledger

    subgraph Stack["Verification Stack"]
        D["BRC-0092:<br/>Base Token Encoding"]
        C["BRC-0107:<br/>Commitment Verification"]
        B["BRC-0042:<br/>Deterministic Key Derivation"]
        A["BRC-0108:<br/>Identity Certificate Link"]
    end

    Core --- Stack
Loading

Terminology

Term Definition
Identity-Linked Token (ILT) A token output containing a valid BRC-0108 certificate hash.
Compliance Profile A structured set of rules defining identity requirements for token usage.
Derivation Scope The deterministic key domain created using BRC-0042.
Selective Revelation Bundle A minimally sufficient encrypted proof package revealing only required certificate fields.
SPV Proof Package A format containing transaction data plus Merkle proof (optionally BRC-0067-formatted).

Normative Rules

1. Identity Binding

A token SHALL be treated as identity-linked if:

  1. The token output contains a BRC-0108 certificate hash, AND
  2. The spending signature is produced using a key derived per BRC-0042 from the certificate root.

If either condition is not met, BRC-115 SHALL NOT apply.

2. Deterministic Key Derivation

All operational keys MUST be derived using:

BRC-0042(master_certificate_entropy, assetId, purposeId)

Use of BIP-32, SLIP-10, hardened derivation paths, or external hierarchical schemes is NOT permitted.

3. Signature Requirements

Identity-linked token transfers MUST be signed using:

SIGHASH_SINGLE | SIGHASH_ANYONECANPAY

Exceptions are permitted ONLY in:

  • Custodial batch aggregation
  • Minting
  • Time-locked recovery workflows

Such exceptions MUST be explicitly signaled using BRC metadata.

4. Protocol Signaling

BRC-115 shall activate under a hybrid signaling model:

  • Implicit activation: Any transaction using identity metadata (BRC-0108) and BRC-0042-derived signatures SHALL be treated as BRC-115-compliant.
  • Explicit activation (optional): A protocol identifier MAY appear in metadata (e.g., 0115, 0115.1) for version governance.

Explicit signaling supersedes implicit interpretation.

5. Mandatory Verification Flow

A compliant verifying wallet MUST validate in the following order:

  1. Token encoding validity (BRC-0092)

  2. Commitment integrity (BRC-0107)

  3. SPV validity (Merkle proof)

  4. Identity certificate presence & authenticity (BRC-0108)

  5. Deterministic derivation match (BRC-0042)

  6. Compliance profile evaluation (rules + selective revelation)

Failure at any stage MUST reject the transfer.

Compliance Profiles

Profile Required Identity Level Typical Use
Open None Standard fungible tokens
Identity-Present Certificate exists Membership, access tokens
Restricted Field-level selective revelation Age verification, region gating
Regulated Certificate type + rules Securities and compliance tokens
Recovery-Capable Secondary derivation Lost-key account recovery

Verification Process

flowchart TD
  A[Parse Token] --> B[Commitment Check]
  B --> C[SPV Check]

  C --> D{Identity Linked?}

  D -->|No| H[ACCEPT]

  D -->|Yes| E[Certificate + Key Binding Check]
  E --> F[Compliance Profile Enforcement]
  F --> G{Accept?}
  G -->|Yes| H2[ACCEPT]
  G -->|No| I[REJECT]
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Reference Implementation Guidance (Non-Normative)

Developers SHOULD:

  • Cache certificates to avoid repeated revelation requests
  • Use temporary encryption keys for field-level exchanges
  • Display meaningful compliance failure messages to improve UX
  • Support offline verification when proof bundles are present

Test Vectors

Vector 1 — Valid Identity-Linked Transfer

Expected Result: Accept

Vector 2 — Invalid Key Derivation

Expected Result: Reject

Vector 3 — Identity Valid, Compliance Failed (e.g., age restriction)

Expected Result: Reject

Additional machine-readable vectors SHALL accompany the reference implementation.

Backward Compatibility

Case Result
Non-identity tokens Unaffected
Legacy wallets MAY ignore identity fields
Identity-linked tokens spent without proper key derivation MUST reject

Security Considerations

  • Commitment chaining prevents replay attacks
  • SPV trust model maintained; no overlay dependency
  • Selective revelation prevents unnecessary personal data exposure
  • Recovery derivation prevents permanent loss without custodianship
  • Prohibition of non-BRC-0042 HD schemes prevents fragmentation

References

  • BRC-0042: Deterministic Key Derivation
  • BRC-0092: Mandala Token Protocol
  • BRC-0107: Commitment-Based Token Integrity
  • BRC-0108: Identity-Linked Token Metadata
  • BRC-0067: (Optional) SPV Packaging Format