Per ZIP 316, the Sapling FVK Encoding only includes `(ak, nk, ovk, dk)`
which is a subset of the Sapling `ExtendedFullViewingKey`. We therefore
need to use `DiversifiableFullViewingKey` inside `UnifiedFullViewingKey`
in order to make it parseable from the UFVK string encoding.
`zcash_client_sqlite::wallet::get_extended_full_viewing_keys` has been
removed as a consequence of this change: we can no longer reconstruct
the correct `ExtendedFullViewingKey` from the `UnifiedFullViewingKey`.
This change modifies note encryption and decryption functions
to treat a shielded output as a single value instead of handling
the parts of an output as independent arguments.
The MemoBytes struct is a minimal wrapper around the memo bytes, and only
imposes the existence of null-padding for shorter memos. The only error
case is attempting to construct a memo that is too long. MemoBytes is
guaranteed to be round-trip encodable (modulo null padding).
The Memo enum implements the additional memo rules defined in ZIP 302,
interpreting the contents of a memo (for example, parsing it as text).
In the interest of making the library usable for both
testnet and mainnet without recompilation, static resolution
of network parameters has been replaced with a parameter passed
to the relevant functions. This also moves addres prefix constants
into the network parameters.
We don't need to check if epk is in the prime-order subgroup before we
trial-decrypt, which saves a third of the cost of trial-decrypting
outputs that are not ours.