Wallet encryption

Marco74 · March 21, 2018, 12:30am

Hi there! I would like to know why the wallet encryption is disable?

Thanks
Marco

scorn · April 19, 2018, 2:59pm

See these:

github.com/zcash/zcash

Figure out a way to prevent apparent balance inconsistencies for locked wallets

opened 07:30PM - 13 Oct 16 UTC

str4d

I-SECURITY A-wallet usability I-error-handling A-rpc-interface

We inherited wallet encryption from Bitcoin, where the transparent addresses are… stored unencrypted in the wallet (so incoming transactions can be identified) but the private keys are stored encrypted (so funds cannot be spent without the master key). We have extended this to shielded addresses: we store z-addrs and their viewing keys unencrypted, and z-keys encrypted. This ensures that wallet encryption maintains the same semantics - someone with the wallet.dat but not the master key can detect transactions belonging to the wallet, but not spend any funds. We also cache unencrypted the note nullifiers for notes we receive, in order to detect when a note is spent. Specifically, it is required in order to detect "pure" spends - JoinSplits that have our notes as inputs, but no output notes come back to us (ie. there is no change, or the change address is not in this wallet). Without access to the nullifiers, the wallet cannot detect these transactions, and will overestimate the available balance. However, nullifiers can only be calculated from notes using the spending key. This means that when the wallet is locked, nullifiers cannot be cached for received notes (#1502). Thus in some atypical but plausible use cases, the RPC balance methods will show more available Zcash than can actually be spent. This behaviour is reset every time the wallet is unlocked, at which point nullifiers can be cached (#1520). We should investigate possible ways to alter computation of nullifiers such that we can calculate them from unencrypted information, without needing to store the spending key unencrypted. This might be via a "linking key" that enables connecting received notes to their spends, or via a delegated detection mechanism (#288). Alternatively, we could not cache the nullifiers, or encrypt them in the wallet. Then the user would need to unlock the wallet in order to view their available balance, which is fundamentally different semantics to upstream Bitcoin. It would not solve the issue of the wallet failing to detect pure spends.

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Wallet encryption

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