feat: add account derivation functions for extended private keys

[QuantumExplorer]

This was done to have an easier way for clients to access private keys for viewing.

Summary by CodeRabbit

• New Features

  • Expanded key derivation: derive extended/private keys from seed or mnemonic, and by index.
  • Added support for BLS and EdDSA account key derivations.
  • Optional WIF output for derived private keys.
  • Path utilities for BIP44, CoinJoin, and identity-related paths.
  • Master key creation and xpriv/xpub conversions with fingerprinting.

• Bug Fixes

  • None.

• Documentation

  • Updated public API docs to include new derivations and revised function counts.

• Tests

  • Added tests for new derivation flows; removed legacy DIP9 tests.

• Revert

  • Removed legacy DIP9 identity key derivation.

[coderabbitai]

Caution

Review failed

The pull request is closed.

Walkthrough

Adds a new account_derivation FFI module and public APIs for deriving extended/private keys from xpriv, seed, or mnemonic (including BLS and EdDSA variants), updates headers and docs, introduces supporting key wrappers, and extends core AccountDerivation trait/impls. Removes DIP9 identity key derivation API and its tests; wires the new module in lib.

Changes

Cohort / File(s)	Change Summary
Docs (FFI API) key-wallet-ffi/FFI_API.md	Documents new account derivation FFI functions (ECDSA, BLS, EdDSA), updates function counts, and removes DIP9 identity derivation entry.
Public FFI Header key-wallet-ffi/include/key_wallet_ffi.h	Adds account_derive_* APIs, BLS/EdDSA mnemonic/seed derivations, derivation helpers (paths, xpriv/xpub conversions, master key, free fns); removes FFIDerivationPathType and dip9_derive_identity_key.
New FFI Module + Tests key-wallet-ffi/src/account_derivation.rs, key-wallet-ffi/src/account_derivation_tests.rs	Introduces FFI account derivation implementations with pointer/error handling and feature-gated BLS/EdDSA flows; adds tests covering success/failure cases and null-safety.
Derivation Cleanup key-wallet-ffi/src/derivation.rs, key-wallet-ffi/src/derivation_tests.rs	Deletes DIP9 FFI function and its tests; no replacement in this file.
FFI Key Internals key-wallet-ffi/src/keys.rs	Adds internal constructors/accessors for FFIExtendedPrivateKey and FFIPrivateKey to support new flows.
Module Wiring key-wallet-ffi/src/lib.rs	Exposes new account_derivation module.
Core Trait Expansion key-wallet/src/account/derivation.rs	Expands AccountDerivation trait to include PrivKey type; adds defaults_to_hardened_derivation, has_internal_and_external, has_intermediate_derivation, and seed/mnemonic/xpriv-based derivation helpers.
Account Implementations (ECDSA/BLS/EdDSA) key-wallet/src/account/mod.rs, key-wallet/src/account/bls_account.rs, key-wallet/src/account/eddsa_account.rs	Updates impls to new trait signature; implements new methods and intermediate-derivation behaviors; adds seed/mnemonic/xpriv-to-private/extended key derivations.

Sequence Diagram(s)

sequenceDiagram
  autonumber
  actor Caller
  participant FFI as FFI account_derive_private_key_from_mnemonic
  participant Acc as Account (Rust)
  participant Der as AccountDerivation Trait
  participant Mn as Mnemonic
  participant Seed as Seed Derivation

  Caller->>FFI: account_derive_private_key_from_mnemonic(account, mnemonic, passphrase, index)
  FFI->>FFI: Validate pointers, init FFIError
  FFI->>Mn: parse mnemonic
  Mn-->>FFI: Mnemonic or error
  FFI->>Seed: to_seed(mnemonic, passphrase)
  Seed-->>FFI: seed bytes
  FFI->>Acc: account.inner()
  Acc->>Der: derive_from_seed_private_key_at(seed, index)
  Der-->>FFI: PrivateKey or error
  alt success
    FFI-->>Caller: FFIPrivateKey*
  else error
    FFI-->>Caller: null + FFIError
  end

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sequenceDiagram
  autonumber
  actor Caller
  participant FFI as FFI account_derive_private_key_at
  participant Acc as Account (Rust)
  participant Der as AccountDerivation Trait

  Caller->>FFI: account_derive_private_key_at(account, master_xpriv, index)
  FFI->>FFI: Validate pointers, ensure not watch-only
  FFI->>Acc: account.inner()
  Acc->>Der: derive_from_master_xpriv_private_key_at(master_xpriv, index)
  Der-->>FFI: PrivateKey or error
  alt success
    FFI-->>Caller: FFIPrivateKey*
  else error
    FFI-->>Caller: null + FFIError
  end

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Estimated code review effort

🎯 4 (Complex) | ⏱️ ~75 minutes

Possibly related PRs

• feat: build out key-wallet ffi and improve ci #108 — Earlier derivation module work that introduced DIP9 identity derivation now being removed here and complemented by new account-level APIs.
• refactor: removed watch only unused #120 — Changes around FFIDerivationPathType and DIP9 interfaces align with this PR’s removal of the enum and function.
• refactor: clean up key wallet some more #121 — Adds/adjusts account-level FFI and crypto scheme support similar to this PR’s new BLS/EdDSA derivations.

Poem

A nibble, a hop, through mnemonic fields I roam,
Seeds sprout keys, along paths I call home.
BLS and EdDSA join my warren’s lore,
DIP9’s old burrow—used no more.
With WIFs in whiskers and xprivs in tow,
I sign the wind—then off I go! 🐇🔑

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📥 Commits

Reviewing files that changed from the base of the PR and between bc2a532 and 7ce3209.

📒 Files selected for processing (12)

• key-wallet-ffi/FFI_API.md (7 hunks)
• key-wallet-ffi/include/key_wallet_ffi.h (1 hunks)
• key-wallet-ffi/src/account_derivation.rs (1 hunks)
• key-wallet-ffi/src/account_derivation_tests.rs (1 hunks)
• key-wallet-ffi/src/derivation.rs (0 hunks)
• key-wallet-ffi/src/derivation_tests.rs (0 hunks)
• key-wallet-ffi/src/keys.rs (1 hunks)
• key-wallet-ffi/src/lib.rs (1 hunks)
• key-wallet/src/account/bls_account.rs (3 hunks)
• key-wallet/src/account/derivation.rs (3 hunks)
• key-wallet/src/account/eddsa_account.rs (2 hunks)
• key-wallet/src/account/mod.rs (3 hunks)

✨ Finishing Touches

• 📝 Generate Docstrings

🧪 Generate unit tests

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch featadd-account-derivation-functions

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[github-actions]

⚠️ FFI Documentation Update Required

The FFI API documentation is out of date. Please regenerate it by running:

For key-wallet-ffi:

cd key-wallet-ffi
make update-docs

For dash-spv-ffi:

cd dash-spv-ffi
make update-docs

Then commit the changes:

git add */FFI_API.md
git commit -m "docs: update FFI API documentation"

This ensures the documentation stays in sync with the actual FFI functions.