`Wallet` makes one, adopts one from a phrase somebody typed, and reads the
phrase back; the vault seals the record at rest.
🔴 The property guarded hardest is a NEGATIVE one: a wallet must not be
derivable from the account. The entropy is fresh randomness — never the
passphrase, the handle, or the Flamenet identity. Deriving it from the
passphrase would be convenient, would need no backup at all, and would tie
every payment somebody ever received to their handle on a public ledger for
ever. The chain does not forget, so there is no undoing it later. A test
asserts that eight wallets made in a row share nothing, which is what would
catch that shortcut being taken.
🔴 The record stores the ENTROPY, never the seed. The seed is a one-way
function of the phrase, so a record holding it would open the wallet and be
unable to produce the words: somebody who lost their phrase but still had their
account could spend, and could never write it down again or move to another
wallet. Self-custody in name only.
⚠️ Erasing the device destroys the record, and the phrase is then the only copy
that exists. Checked rather than assumed while writing this: plain sign-out
keeps the vault and `updatePassword` uses the plain door, so a password change
does NOT cost somebody their wallet; `signOut(erasingDevice = true)` and
`deleteAccount` destroy it. That is what a recovery phrase is for, and it has to
be said at the moment the phrase is shown rather than discovered afterwards.
⚠️ An imported phrase is validated BEFORE it is stored. One that fails its
checksum is refused at import rather than saved and discovered later, when the
wallet it names turns out to be empty and nobody can say why.
⚠️ The receive counter is carried across a rewrite rather than reset. Resuming
at zero would hand out addresses somebody has already been paid at, undoing the
one linkability a wallet can prevent.
⚠️ `SecureRandom()` with no seeding call. Seeding it from a timestamp or a
device id would make the wallet reconstructible from things that are not
secret — the same failure as deriving it from the passphrase, wearing a
different hat.
9 tests. App builds, every JVM suite green.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
