Wallet Tech Notes

Wallet should follow the following specs:
- BIP23 HD Wallet
- BIP39 (Paper wallet)
- BIP39 (Mnemonic backups)
- BIP44 (Multi-purpose passphrase protected HD wallet)
See account file format spec in Accounts
We need to register coin ID for Spacemesh Coin (SMC) and for each testnet Spacemesh Coin (SMCT1, SMCT2, etc...) See BIP44 and BIP44 LIST

Wallet App -> Wallet -> {NetworkId, Accounts} -> Default Account (key pair at index 0)

Passphrases and Paper Backups

We use BIP39 for 12 words mnemonic from a random seed generation for purposes of paper backups
We use a user-provided passphrase to create a derived key that is harder to brute-force regardless of user's passphrase strength. See 'From Mnemonic to Seed' in BIP39
An HD Wallet data file stores the seed encrypted with the derived key. To access the private seed (and the wallet addresses and 12 words mnemonic code) user must provide his passphrase and have access to the wallet's data file
User can recreate the data file in case he or she lost the passphrase using the 12 words mnemonic from a paper backup

Random Seed (512 bits) -> 12 words Mnemonic -> BIP32 Root Key -> BIP44 HD Wallet

User passphrase -> KDF -> Decrypt Random Seed (512 bits) from wallet file -> Access BIP44 HD Wallet or 12 words mnemonic

BIP32 Considerations

A Spacemesh wallet is a BIP44 HD Wallet with the following path rules:

m / 44 / NetId / account / change / address[i]

m and 44 - BIP32 constants
NetId - one of the Spacemesh networks, e.g. MainNet, TestNet1, TestNet2, etc...
change - 0 constant (not applicable to Spacemesh Coins)
account - 0 constant - for now. May change in the future.
`address[i] - addresses key pairs array.

Note that Spacemesh accounts are technically BIP32 address pairs and the default wallet account is address[0] and the we don't use the BIP32 accounts feature. Accounts is always constant 0 in a Spacemesh wallet. This may change in the future to support more advanced use cases (mainly multiple sub-wallets, each with its own accounts, in one wallet).

So, we use BIP44 with only account 0 and what we communicate to users as accounts are actually BIP44 addresses.

Examples: m/44/665/0/0/address[0] - the default account for Spacemesh mainnet (netId 665). m/44/666/0/0/address[0] - the default account for Spacemesh testnet1 (netId 666). m/44/666/0/0/address[1] - Second account for Spacemesh testnet1 (netId 666).

Additional Info

BIP39 Mnemonic code for generating deterministic keys and BIP38 paper wallets. Read more at the official BIP38 BIP39 specs
BIP32 Hierarchical Deterministic (HD) Wallets. Read more at the official BIP32 spec
See the demo at bip32.org
BIP44 Multi-Account Hierarchy for Deterministic Wallets. Read more at the official BIP44 spec
Keys are never stored in the cloud - only locally on the device, and store is encrypted with a key derived from user provided passphrase (or bio auth measure)