feat: add BIP-85 child mnemonic derivation + Lynx coin#385
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BitHighlander wants to merge 5 commits intodevelopfrom
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feat: add BIP-85 child mnemonic derivation + Lynx coin#385BitHighlander wants to merge 5 commits intodevelopfrom
BitHighlander wants to merge 5 commits intodevelopfrom
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- Point device-protocol and python-keepkey submodules to upstream master (includes BIP-85, Solana, Tron, TON wire IDs and proto definitions) - Add nanopb .options files for Solana, Tron, TON (field size constraints) - Add Bip85Mnemonic.mnemonic max_size:241 to messages.options - Update lib/transport/CMakeLists.txt with new proto sources, options, headers, and protoc compilation commands - Fix CI: use pre-installed clang-format instead of apt-get install (eliminates 3-minute timeout on GitHub runners) - Update Zcash transparent branch ID from Sapling to NU6
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Add Lynx cryptocurrency support to the firmware coins table. Parameters sourced from Lynx Core (Bitcoin v26 fork with PoS): - SLIP-44 coin type: 191 (0x800000BF) - Address type: 45 (pubkey hash), 22 (script hash) - SegWit enabled with bech32 prefix "lynx" - Taproot enabled - Standard Bitcoin xpub/ypub/zpub magic numbers - Signed message header: "Bitcoin Signed Message:\n" (matches upstream) - 8 decimal places, secp256k1 curve
Add BIP-85 support for deriving child mnemonics from the device seed. Supports 12, 18, and 24 word mnemonics via HMAC-SHA512 derivation on path m/83696968'/39'/0'/<word_count>'/<index>'. New files: - bip85.h/bip85.c: Core derivation using trezor-crypto primitives - fsm_msg_bip85.h: FSM handler for GetBip85Mnemonic message Integration: fsm.h, fsm.c, messagemap.def, firmware CMakeLists.txt device-protocol bumped to 17b38803e (includes BIP-85 message defs)
- Reject index >= 0x80000000 to prevent hardened-bit derivation collision - Add has_word_count/has_index field presence checks - Change confirmation text from "Derive" to "Export" to convey secret export - Add second confirmation before sending child mnemonic to host
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Required proto fields don't generate has_ members in nanopb. word_count and index are guaranteed present by the proto schema. Co-Authored-By: Claude Opus 4.6 <[email protected]>
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Motivation
BIP-85: Users need deterministic child mnemonics derived from their master seed for isolated wallet compartments (e.g., hot wallet derived from cold storage seed). BIP-85 (Deterministic Entropy From BIP32 Keychains) is the established standard for this, supported by Trezor, Coldcard, and others. Without it, users must manage multiple independent seeds.
Lynx: Community-requested UTXO coin addition. Lynx (LYNX) is a Bitcoin fork with identical transaction structure — the coins table entry is sufficient, no new signing logic required.
Changes
BIP-85 (
lib/firmware/bip85.c,fsm_msg_bip85.h):m/83696968'/39'/0'/{index}'"bip-entropy-from-k"per specGetBip85Mnemonic(120) →Bip85Mnemonic(121)Code review fixes applied:
has_checks on required nanopb fieldsmemzero()in all exit pathsLynx:
coins.deftable (name, shortcut, SLIP44 coin type, address prefix)Risk assessment
bip32andhmacprimitives from trezor-crypto. Key material is derived and displayed but never stored.Testing
requires_firmware()