Context

Nexum must define standard derivation paths for multiple key types: smart account keys, storage keys (for Swarm), and deterministic discovery mechanisms. These standards enable secure, reproducible key generation across different use cases.

Considerations

This specification should address the following considerations:

• BIP-32/BIP-44 compliance and extensions
• Derivation paths for EOA wallets
• Derivation paths for smart account control keys (delegation keys)
• Derivation paths for system keys (registry framework)
• Derivation paths for identity-specific keys (profile isolation)
• Deterministic discovery of derived accounts
• Account gap limits and scanning
• Hardened vs non-hardened derivation choices
• Compatibility with existing wallet standards
• Integration with Keycard derivation capabilities

Solution

Documented in NXP-1: Derivation Path Standards.

Key features:

• Index Space Partitioning: SYSTEM_OFFSET (2³⁰) separates user accounts from system keys
• Delegation Keys: Zero-metadata discovery for multisig/EIP-7702 delegation
• System Key Registry: Framework for NXP specifications to allocate reserved indices
• BIP-32 Compliance: Deterministic retry algorithm for edge cases

Dependencies

Depends on (Phase 2):

• docs: design identity model specification #84 (Identity model must be defined first to understand key hierarchy)

Blocks:

• docs: design storage architecture #87 (Storage architecture needs encryption key derivation)

Out of Scope

• Implementation of cryptographic primitives
• Keycard-specific implementation details
• Account recovery mechanisms
• Specific system key allocations (defined by separate NXPs, e.g., NXP-2 for storage)

References

• Standards: BIP-32, BIP-39, BIP-44, SLIP-44, EIP-1581
• Related: docs: design identity model specification #84 (Identity model), docs: design storage architecture #87 (Storage architecture), feat: integrate Keycard with derivation standards #95 (Keycard integration)
• Epic: [EPIC 0.0] Foundation - Identity & Account Architecture pm#3 (Foundation)