Derive transparent (t-addr) keys from the HD seed and add BIP39 mnemonic seed
phrases that are byte-for-byte compatible with SilentDragonXLite, so the same
24 words recover the same shielded and transparent addresses in either wallet.
HD transparent keys:
- Derive t-keys from the seed at m/44'/coin'/0'/0/i (were random CKeys).
- CHDChain gains a version-gated transparent counter; existing wallets load
unchanged. GenerateNewKey routes through DeriveNewChildKey when enabled
(-hdtransparent, default on).
- Restore from a seed hex via -hdseed with gap-limit pre-derivation; birthday
pinned to genesis so the rescan is not clipped.
BIP39 seed phrases:
- Wire the vendored trezor BIP39 lib (src/crypto/bip39) into the build, fix its
BIP39_WORDS guard, and disable the insecure mnemonic cache.
- Match SDXLite exactly: English wordlist, empty passphrase, PBKDF2 64-byte
seed, coin type 141, ZIP-32 m/32'/141'/i' and BIP44 m/44'/141'/0'/0/i. Store
the 32-byte entropy and expand to the 64-byte seed on demand.
- Restore via -mnemonic, create via -usemnemonic, reveal via z_exportmnemonic.
Verified by gtests including a known-answer BIP39 seed vector and z/t address
derivation checks (src/gtest/test_hdtransparent.cpp, test_mnemonic_compat.cpp).
Docs in doc/hd-transparent-keys.md and doc/seed-phrase.md.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
