54 lines
2.8 KiB
Markdown
54 lines
2.8 KiB
Markdown
# Wallet system
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Bcoin maintains a wallet database which contains every wallet. Wallets are
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_not usable_ without also using a wallet database. For testing, the wallet
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database can be in-memory, but it must be there.
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Wallets in bcoin are based on BIP44. They also originally supported BIP45 for
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multisig, but support was removed to reduce code complexity, and also because
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BIP45 doesn't seem to add any benefit in practice.
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The wallet database can contain many wallets, with many accounts, with many
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addresses for each account. Bcoin should theoretically be able to scale to
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hundreds of thousands of wallets/accounts/addresses.
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## Deviation from BIP44
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**It's important to backup the wallet database.** There are several deviations
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from [BIP44](https://github.com/bitcoin/bips/blob/master/bip-0044.mediawiki)
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that break the determinsitic algorithm, and therefore it's recommended to
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backup the wallet database any time an account is created, as there are several
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possible configurations of an account.
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There is a command available via the wallet RPC called `backupwallet` that can
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clone the database to a new destination. There are also the RPC calls
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`dumpwallet` and `dumpprivkey` for exporting private keys. After shutting down
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the wallet process, it's also possible to copy the LevelDB database from the
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default location at `~/.bcoin/wallet` for main net or
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`~/.bcoin/<network>/wallet` for others. Copying LevelDB while the process is
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running can result in a corrupted copy. LevelDB is also prone to
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[database corruption](https://en.wikipedia.org/wiki/LevelDB#Bugs_and_reliability).
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Each account can be of a different type. You could have a pubkeyhash account,
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a multisig account, and a witness pubkeyhash account all in the same wallet.
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Accounts can be configured with or without Segregated Witness and both base58
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(nested-in-P2SH) and bech32 (native) P2WPKH addresses can be derived from the
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same account.
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Bcoin adds a third branch to each account for nested SegWit addresses.
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Branch `0` and `1` are for `receive` and `change` addresses respectively
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(which is BIP44 standard) but branch `2` is used by bcoin to derive
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[nested SegWit addresses.](https://github.com/bitcoin/bips/blob/master/bip-0141.mediawiki#P2WPKH_nested_in_BIP16_P2SH)
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Accounts in a bcoin wallet can be configured for multisig and import xpubs
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from cosigners. Externally-generated Extended Private Keys (`xpriv`) and non-HD
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single address private keys can all be imported into a bcoin wallet. Balances
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of those addresses can be watched as well spent from (in the case of a private
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key).
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Unlike [BIP44](https://github.com/bitcoin/bips/blob/master/bip-0044.mediawiki),
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bcoin does not limit account depth and a new account can be created
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after an empty account. This can create issues with deterministic account
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discovery from the master node (seed) as there are `2 ^ 31 - 1` _(worst case)_
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possible accounts to search.
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