Key Model

The 3-level key hierarchy — master wallet, slot families, and webcash 4-chain derivation.

Three Levels

Level	What	How
1. Master Wallet	BIP39 mnemonic (24 words)	BIP32 hardened derivation into slot families
2. Slot Families	Independent 32-byte secrets	One slot per purpose: webcash, bitcoin, RGB, vouchers, PGP
3. Webcash Chains	4 SHA256 chains per webcash slot	RECEIVE, PAY, CHANGE, MINING — each with unlimited depth

The master wallet is not a webcash wallet. It is a keychain that contains webcash wallets, bitcoin wallets, RGB identities, voucher wallets, and PGP signing keys as derived slots.

Level 1: Master Wallet

A single BIP39 mnemonic (24 words, 256-bit entropy) generates all keys. The BIP32 derivation path:

m / 83696968' / 0' / family' / index'

All indices are hardened. No public key derivation, no leakage between slots.

The master database stores: root mnemonic, wallet slot registry, PGP identity registry, RGB contracts, and certificates. It does not store webcash balances or bitcoin UTXOs — those live in per-slot databases.

Level 2: Slot Families

Family	Max Slots	Purpose
webcash	256	Bearer e-cash. Each slot initializes a webylib HDWallet with 4 SHA256 chains.
bitcoin	256	On-chain Bitcoin via BIP86 (Taproot) and BIP84 (SegWit). ARK off-chain protocol.
rgb	256	Client-side validated smart contracts. Multiple witness backends (Bitcoin, Webcash Witness, Harmoniis Witness).
voucher	256	Bearer credits from voucher service providers.
pgp	1000	Ed25519 signing identities for authentication and contract signing.

Labeled wallets

Within each family, multiple labeled sub-wallets exist at different slot indices. Each is an independent BIP32 derivation with its own database:

webcash[0] = "main"         (main_webcash.db)
webcash[1] = "savings"      (savings_webcash.db)
webcash[2] = "cloudminer"   (cloudminer_webcash.db)

Level 3: Webcash 4-Chain Derivation

Each webcash slot produces a 32-byte master secret. This initializes a webylib HDWallet with 4 independent SHA256 chains (not BIP32):

Chain	Code	Used for
RECEIVE	0	Incoming payment secrets
PAY	1	Outgoing payment outputs
CHANGE	2	Transaction change
MINING	3	Mining reward collection

Derivation

tag    = SHA256("webcashwalletv1")
secret = SHA256(tag || tag || webcash_master || chain_code_be64 || depth_be64)

Each depth produces a unique secret. Depths increment atomically after each successful server operation.

Visual Summary

BIP39 Mnemonic (24 words)
|
+- BIP32 seed -> master_xpriv
   |
   +- m/83696968'/0'/ (Harmoniis purpose)
      |
      +- /2'/0' --- webcash[0]  -> 32-byte webcash master --+
      +- /2'/1' --- webcash[1]  -> labeled wallet           |
      +- /3'/0' --- bitcoin[0]  -> BIP86/BIP84 seed         |
      +- /1'/0' --- rgb[0]      -> RGB contract identity    |
      +- /6'/0' --- voucher[0]  -> voucher master           |
      +- /4'/0' --- pgp[0]      -> Ed25519 signing key      |
      +- /4'/1' --- pgp[1]      -> labeled identity         |
                                                             |
         +---------------------------------------------------+
         |  webylib HDWallet (SHA256, NOT BIP32)
         |
         +- RECEIVE (0) -- depth 0, 1, 2, ...
         +- PAY     (1) -- depth 0, 1, 2, ...
         +- CHANGE  (2) -- depth 0, 1, 2, ...
         +- MINING  (3) -- depth 0, 1, 2, ...

Recovery

With just the 24-word mnemonic, the wallet reconstructs everything:

Derive master BIP32 key from mnemonic
Derive all slot families at their known indices
For each webcash slot: scan all 4 chains up to the gap limit (default: 20)
For PGP: scan indices 0..999
For bitcoin: sync via Esplora/Electrum

A webcash master secret (64-char hex, not the mnemonic) can recover only that webcash slot's funds. Other families are not recoverable from a single slot secret.