Release 4.7.0 marks a major milestone on the path to NU5. It enables full support for the Orchard shielded protocol and Unified Addresses on testnet. Unified Addresses can also start being used on mainnet, but funds cannot be sent to an Orchard receiver until NU5 activates on mainnet. Release 4.7.0 will also reactivate NU5 on testnet to pick up the latest consensus changes. That reactivation is set to occur on or about April 22nd. The Zcash Schedule page has been updated to reflect the 4.7.0 release as well as the testnet reactivation timing.
Pre-packed Linux binaries for 4.7.0 will be available later today.
Changes to Testnet NU5 Consensus Rules
NOTE: All testnet nodes that have been running on testnet above height 1599200 will need to upgrade to
v4.7.0 and then run with
- In order to better support hardware wallets, transparent signature hash construction as defined in ZIP 244 has been modified to include a hash of the serialization of the amounts of all outputs being spent, along with a hash of all spent outputs
scriptPubKeysvalues, except in the case that the
ANYONECANPAYflag is set. This allows hardware wallet devices to verify the UTXO amounts without having to stream all the previous transactions containing the outputs being spent to the device. Also as part of these changes, the transparent signature hash digest now commits directly, rather than implicitly, to the sighash type, and the sighash type is restricted to a fixed set of valid values. The change to ZIP 244 can be seen here.
- This release fixes a bug in
v4.6.0that caused a consensus failure on the Zcash testnet at height
- There have been changes to the Halo2 proving system to improve consistency between the specification and the implementation, and these may break compatibility.
- There have been numerous changes to the Orchard circuit implementation since
v4.6.0. A complete list can be found here.
- A potential Faerie Gold vulnerability affecting the previous activation of NU5 on testnet and existing since
v4.6.0has been mitigated.
NU5 Testnet Reactivation
To support the aforementioned testnet consensus changes, the following changes are made in
- The consensus branch ID for NU5 is changed to
- The protocol version indicating NU5-aware testnet nodes is set to
- The testnet reactivation height for NU5 is set to 1,842,420.
As mentioned above, all testnet nodes that have been running on testnet above height 1,599,200 will need to upgrade to
v4.7.0 and then run with
Emergency Recovery Phrases
The zcashd wallet has been modified to support BIP 39, which describes how to derive the wallet’s HD seed from a mnemonic phrase, hereafter known as the wallet’s “emergency recovery phrase”. The emergency recovery phrase will be generated on load of the wallet, or the first time the wallet is unlocked, and is available via the
z_exportwallet RPC call. All new addresses produced by the wallet are now derived from this seed using the HD wallet functionality described in ZIP 32 and ZIP 316. For users upgrading an existing Zcashd wallet, it is recommended that the wallet be backed up prior to upgrading to the 4.7.0 Zcashd release. In the remainder of this document, the HD seed derived from the emergency recovery phrase will be termed the wallet’s “mnemonic seed”.
Following the upgrade to 4.7.0, Zcashd will require that the user confirm that they have backed up their new emergency recovery phrase, which may be obtained from the output of the
z_exportwallet RPC call. This confirmation can be performed manually using the
zcashd-wallet-tool utility that is supplied with this release (built or installed in the same directory as
zcashd). The wallet will not allow the generation of new addresses until this confirmation has been performed. It is recommended that after this upgrade, funds tied to preexisting addresses be migrated to newly generated addresses so that all wallet funds are recoverable using the emergency recovery phrase going forward. If you choose not to migrate funds in this fashion, you will continue to need to securely back up the entire
wallet.dat file to ensure that you do not lose access to existing funds; EXISTING FUNDS WILL NOT BE RECOVERABLE USING THE EMERGENCY RECOVERY PHRASE UNLESS THEY HAVE BEEN MOVED TO A NEWLY GENERATED ADDRESS FOLLOWING THE 4.7.0 UPGRADE.
In the case that your wallet previously contained a Sapling HD seed, the emergency recovery phrase is constructed using the bytes of that seed, such that it is possible to reconstruct keys generated using that legacy seed if you know the emergency recovery phrase. HOWEVER, THIS RECONSTRUCTION DOES NOT FOLLOW THE NORMAL PROCESS OF DERIVATION FROM THE EMERGENCY RECOVERY PHRASE. Instead, to recover a legacy Sapling key from the emergency recovery phrase, it is necessary to reconstruct the bytes of the legacy seed by conversion of the phrase back to its source randomness instead of by hashing as is specified in BIP 39. Only keys and addresses produced after the upgrade can be obtained by normal derivation of a ZIP 32 or BIP 32 master seed using BIP 39.
The zcashd wallet now supports the Orchard shielded protocol.
The zcashd wallet has been modified to alter the way that change is handled. In the case that funds are being spent from a unified account, change is sent to a wallet-internal change address for that account instead of sending change amounts back to the original address where a note being spent was received. The rationale for this change is that it improves the security that is provided to the user of the wallet when supplying incoming viewing keys to third parties; previously, an incoming viewing key could effectively be used to detect when a note was spent (hence violating the “incoming” restriction) by observing change outputs that were sent back to the address where the spent note was originally received.
New RPC Methods
walletconfirmbackupThis newly created API checks a provided emergency recovery phrase against the wallet’s emergency recovery phrase; if the phrases match then it updates the wallet state to allow the generation of new addresses. This backup confirmation workflow can be disabled by starting zcashd with
-walletrequirebackup=falsebut this is not recommended unless you know what you’re doing (and have otherwise backed up the wallet’s emergency recovery phrase anyway). For security reasons, this RPC method is not intended for use via
zcash-clibut is provided to enable
zcashd-wallet-tooland other third-party wallet interfaces to satisfy the backup confirmation requirement. Use of the
zcash-cliwould risk that the emergency recovery phrase being confirmed might be leaked via the user’s shell history or the system process table;
zcashd-wallet-toolis provided specifically to avoid this problem.
z_getnewaccountThis API allows for creation of new BIP 44 / ZIP 32 accounts using HD derivation from the wallet’s mnemonic seed. Each account represents a separate spending authority and source of funds. A single account may contain funds in the Sapling and Orchard shielded pools, as well as funds held in transparent addresses.
z_listaccountsThis API returns the list of BIP 44 / ZIP 32 accounts that are being tracked by the wallet.
z_getaddressforaccountThis API allows for creation of diversified unified addresses under a single account. Each call to this API will, by default, create a new diversified unified address containing transparent p2pkh, Sapling, and Orchard receivers. Additional arguments to this API may be provided to request the address to be created with a user-specified set of receiver types and diversifier index.
z_getbalanceforaccountThis API makes it possible to obtain balance information on a per-account basis.
z_getbalanceforviewingkeyThis API allows a user to obtain balance information for funds visible to a Sapling or Unified full viewing key; if a Sprout viewing key is provided, this method allows retrieval of the balance only in the case that the wallet controls the corresponding spending key. This API has been added to supplement (and largely supplant)
z_getbalance. Querying for balance by a single address returns only the amount received by that address, and omits value sent to other diversified addresses derived from the same full viewing key; by using
z_getbalanceforviewingkeyit is possible to obtain a correct balance that includes all amounts controlled by a single spending key, including both those sent to external diversified addresses and to wallet-internal change addresses.
z_listunifiedreceiversThis API allows the caller to extract the individual component receivers from a unified address. This is useful if one needs to provide a bare Sapling or transparent p2pkh address to a service that does not yet support unified addresses.
- The result type for the
listaddressesendpoint has been modified:
keypoolsource type has been removed; it was reserved but not used.
- In the
saplingaddress results, the
zip32AccountIdattribute has been removed in favor of
zip32KeyPath. This is to allow distinct key paths to be reported for addresses derived from the legacy account under different child spending authorities, as are produced by
- Addresses derived from the wallet’s mnemonic seed are now included in
- The results of the
z_exportwalletRPC methods have been modified to now include the wallet’s newly generated emergency recovery phrase as part of the exported data. Also, the seed fingerprint and HD keypath information are now included in the output of these methods for all HD-derived keys.
- The results of the
getwalletinfoRPC have been modified to return two new fields:
legacy_seedfp, the latter of which replaces the field that was previously named
- A new
poolattribute has been added to each element returned by
z_listunspentto indicate which value pool the unspent note controls funds in.
poolattribute has been added to each result to indicate what pool the received funds are held in.
- A boolean-valued
changeattribute has been added to indicate whether the output is change.
- Block metadata attributes
blocktimehave been added to the result.
z_viewtransactionhas been updated to include attributes that provide information about Orchard components of the transaction. Also, the
typeattribute for spend and output values has been deprecated and replaced by the pool attribute.
z_getnotescountnow also returns information for Orchard notes.
- The output format of
z_exportwallethas been changed. The exported file now includes the mnemonic seed for the wallet, and HD keypaths are now exported for transparent addresses when available.
- The result value for
z_importviewingkeynow includes an
address_typefield that replaces the now-deprecated
z_listunspenthas been updated to render unified addresses for Sapling and Orchard outputs when those outputs are controlled by unified spending keys. Outputs received by unified internal addresses do not include the
- Legacy transparent address generation using
getnewaddressno longer uses a preallocated keypool, but instead performs HD derivation from the wallet’s mnemonic seed according to BIP 39 and BIP 44 under account ID
z_gettreestatehas been updated to include information about the Orchard note commitment tree.
z_sendmanyRPC call no longer permits Sprout recipients in the list of recipient addresses. Transactions spending Sprout funds will still result in change being sent back into the Sprout pool, but no other
Sprout->Sprouttransactions will be constructed by the Zcashd wallet.
- The restriction that prohibited
Sprout->Saplingtransactions has been lifted; however, since such transactions reveal the amount crossing pool boundaries, they must be explicitly enabled via a parameter to the
- A new string parameter,
privacyPolicy, has been added to the list of arguments accepted by
z_sendmany. This parameter enables the caller to control what kind of information they permit
zcashdto reveal on-chain when creating the transaction. If the transaction can only be created by revealing more information than the given strategy permits,
z_sendmanywill return an error. The parameter defaults to
LegacyCompat, which applies the most restrictive strategy
FullPrivacywhen a Unified Address is present as the sender or a recipient, and otherwise preserves existing behavior (which corresponds to the
- Since Sprout outputs are no longer created (with the exception of change)
z_sendmanyno longer generates payment disclosures (which were only available for Sprout outputs) when the
-paymentdisclosureexperimental feature flag is set.
- Outgoing viewing keys used for shielded outputs are now produced as described in ZIP 316
- When sending from or to one or more unified addresses, change outputs are now always sent to addresses controlled by the wallet’s internal spending keys, as described in ZIP 316. These addresses are not returned by any RPC API, as they are intended to never be shared with any third party, and are for wallet-internal use only. This change improves the privacy properties that may be maintained when sharing a unified internal viewing key for an account in the wallet.
- In cases where
z_sendmanymight produce transparent change UTXOs, those UTXOs are sent to addresses derived from the wallet’s mnemonic seed via the BIP 44
z_getnewaddresshas been deprecated in favor of
z_listaddresseshas been deprecated. Use
z_getbalancehas been deprecated. Use
z_getbalanceforviewingkeyinstead. See the discussion of how change is now handled under the Wallet heading for additional background.
z_gettotalbalancehas been deprecated. Use
dumpwallethas been deprecated. Use
- Clang has been updated to use LLVM 13.0.1.
- libc++ has been updated to use LLVM 13.0.1, except on Windows where it uses 13.0.0-3.
- The Rust toolchain dependency has been updated to version 1.59.0.
- Debian 9 has been removed from the list of supported platforms.
- Debian 11 (Bullseye) has been added to the list of supported platforms.
- A build issue (a missing header file) has been fixed for macOS targets.
- On Arch Linux only, a copy of Debian’s libtinfo5_6.0 is used to fix a build regression.
- Mining to Orchard recipients is now supported on testnet.
- It is now possible to mine to a Sapling receiver of a unified address.
- Concurrency bugs related to
getblocktemplatehave been fixed via backports from Bitcoin Core.
License information in
contrib/debian/copyright has been updated to be more accurate.