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Add stub for ZIP 225 (Version 5 Transaction Format). Signed-off-by: Daira Hopwood <daira@jacaranda.org>
2021-02-15 13:03:28 -08:00
::
ZIP: 225
Title: Version 5 Transaction Format
Owners: Daira Hopwood <daira@electriccoin.co>
Jack Grigg <jack@electriccoin.co>
Sean Bowe <sean@electriccoin.co>
Kris Nuttycombe <kris@electriccoin.co>
Ying Tong Lai <yingtong@electriccoin.co>
Draft of ZIP 225
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Status: Draft
Add stub for ZIP 225 (Version 5 Transaction Format). Signed-off-by: Daira Hopwood <daira@jacaranda.org>
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Category: Consensus
Discussions-To: <https://github.com/zcash/zips/issues/440>
Draft of ZIP 225
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Terminology
===========
Add stub for ZIP 225 (Version 5 Transaction Format). Signed-off-by: Daira Hopwood <daira@jacaranda.org>
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Draft of ZIP 225
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The key words "MUST" and "MAY" in this document are to be interpreted as described in
RFC 2119. [#RFC2119]_
The term "network upgrade" in this document is to be interpreted as described in ZIP 200
[#zip-0200]_.
Abstract
========
This proposal defines an update to the Zcash peer-to-peer transaction format to include
support for data elements required to support the Orchard protocol [#protocol_nu5]_. The
new transaction format defines well-bounded regions of the serialized form for to serve
each of the existing pools of funds, and adds and describes a new region containing
Orchard-specific elements.
Separate Sapling effecting data from authorizing data in the transaction format. This change restructures the wire format of Sapling spend and output descriptions to segregate authorizing data from the data describing the effects of the transaction in a similar fashion as has been done for Orchard. The result is now symmetric between Sapling and Orchard, and also simplifies slightly the description of the computation of the authorizing data commitment in ZIP 244.
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This ZIP also depends upon and defines modifications to the computation of the values
**TxId Digest**, **Signature Digest**, and **Authorizing Data Commitment** defined by ZIP
244 [#zip-0244]_.
Draft of ZIP 225
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Motivation
==========
The new Orchard shielded pool requires a serialized data elements that are distinct from
any previous Zcash transaction. In addition, with the activation of ZIP 244, the
serialized transaction format will no longer be consensus-critical. It makes sense at this
point to define a format that can readily accommodate future extension in a systematic
fashion, where elements required for support for a given pool are kept separate.
Requirements
============
The new format must fully support the Orchard protocol.
The new format should lend itself to future extension or pruning to add or remove
value pools.
The computation of the non-malleable transaction identifier hash must include all
newly incorporated elements except those that attest to transaction validity.
The computation of the commitment to authorizing data for a transaction must include
all newly incorporated elements that attest to transaction validity.
Non-requirements
================
More general forms of extensibility, such as definining a key/value format that
allows for parsers that are unaware of some components, are not required.
Specification
=============
The Zcash transaction format for transaction version 5 is as follows:
Transaction Format
------------------
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
| Bytes | Name | Data Type | Description |
+=============================+==========================+======================================+============================================================+
| **Common Transaction Fields** |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
|``4`` |``header`` |``uint32`` |Contains: |
| | | | * fOverwintered flag (bit 31, always set) |
| | | | * version (bits 30 .. 0) – transaction version. |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
|``4`` |``nVersionGroupId`` |``uint32`` |Version group ID (nonzero). |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
|``4`` |``lock_time`` |``uint32`` |Unix-epoch UTC time or block height, encoded as in Bitcoin. |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
|``4`` |``nExpiryHeight`` |``uint32`` |A block height in the range {1 .. 499999999} after which |
| | | |the transaction will expire, or 0 to disable expiry. |
| | | |[ZIP-203] |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
| **Transparent Transaction Fields** |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
|``varies`` |``tx_in_count`` |``compactSize`` |Number of transparent inputs in tx_in |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
|``varies`` |``tx_in`` |``tx_in`` |Transparent inputs, encoded as in Bitcoin |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
|``varies`` |``tx_out_count`` |``compactSize`` |Number of transparent outputs in tx_out |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
|``varies`` |``tx_out`` |``tx_out`` |Transparent outputs, encoded as in Bitcoin |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
| **Sprout Transaction Fields** |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
|``varies`` |``nJoinSplits`` |``compactSize`` |The number of JoinSplit descriptions in vJoinSplits |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
|``1698 * nJoinSplits`` |``vJoinSplits`` |``JSDescriptionGroth16[nJoinSplits]`` |A sequence of JoinSplit descrptions using Groth16 proofs, |
| | | |encoded per § 7.2 ‘JoinSplit Description Encoding |
| | | |and Consensus’ |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
|``32`` |``joinSplitPubKey`` |``byte[32]`` |An encoding of a JoinSplitSig public validating key |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
|``64`` |``joinSplitSig`` |``byte[64]`` |A signature on a prefix of the transaction encoding, |
| | | |to be verfied using joinSplitPubKeyas specied in § 4.11 |
| | | |‘Non-malleability (Sprout)’ |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
| **Sapling Transaction Fields** |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
|``varies`` |``nSaplingSpends`` |``compactSize`` |Number of Sapling Spend Descriptions in vSaplingSpends |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
Separate Sapling effecting data from authorizing data in the transaction format. This change restructures the wire format of Sapling spend and output descriptions to segregate authorizing data from the data describing the effects of the transaction in a similar fashion as has been done for Orchard. The result is now symmetric between Sapling and Orchard, and also simplifies slightly the description of the computation of the authorizing data commitment in ZIP 244.
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|``128 * nSaplingSpends`` |``vSaplingSpends`` |``SaplingSpendNU5[nSaplingSpends]`` |A sequence of Sapling Spend Descriptions, encoded per |
Draft of ZIP 225
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| | | |protocol §7.3 "Spend Description Encoding and Consensus" |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
|``varies`` |``nSaplingOutputs`` |``compactSize`` |Number of Sapling Output Decriptions in vSaplingOutputs |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
Separate Sapling effecting data from authorizing data in the transaction format. This change restructures the wire format of Sapling spend and output descriptions to segregate authorizing data from the data describing the effects of the transaction in a similar fashion as has been done for Orchard. The result is now symmetric between Sapling and Orchard, and also simplifies slightly the description of the computation of the authorizing data commitment in ZIP 244.
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|``756 * nSaplingOutputs`` |``vSaplingOutputs`` |``SaplingOutputNU5[nSaplingOutputs]`` |A sequence of Sapling Output Descriptions, encoded per |
Draft of ZIP 225
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| | | |protocol §7.4 "Output Description Encoding and Consensus" |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
|``8`` |``valueBalanceSapling`` |``int64`` |The net value of Sapling spends minus outputs |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
|``32`` |``anchorSapling`` |``byte[32]`` |A root of the Sapling note commitment tree |
| | | |at some block height in the past |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
Separate Sapling effecting data from authorizing data in the transaction format. This change restructures the wire format of Sapling spend and output descriptions to segregate authorizing data from the data describing the effects of the transaction in a similar fashion as has been done for Orchard. The result is now symmetric between Sapling and Orchard, and also simplifies slightly the description of the computation of the authorizing data commitment in ZIP 244.
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|``192 * nSaplingSpends`` |``zkproofsSaplingSpend`` |``byte[192 * nSaplingSpends]`` |Encodings of the zk-SNARK proofs for each SaplingSpend |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
|``64 * nSaplingSpends`` |``spendAuthSigsSapling`` |``byte[64 * nSaplingSpends]`` |Authorizing signatures for each SaplingSpend |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
|``192 * nSaplingOutputs`` |``zkproofsSaplingOutput`` |``byte[192 * nSaplingOutputs]`` |Encodings of the zk-SNARK proofs for each SaplingOutput |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
Draft of ZIP 225
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|``64`` |``bindingSigSapling`` |``byte[64]`` |A Sapling binding signature on the SIGHASH transaction hash |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
| **Orchard Transaction Fields** |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
|``varies`` |``nOrchardActions`` |``compactSize`` |The number of Orchard Action Descriptions in |
| | | |vOrchardActions |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
|``884 * nOrchardActions`` |``vOrchardActions`` |``OrchardAction[nOrchardActions]`` |A sequence of Orchard Action descriptions, encoded per |
| | | |§ 7.5 ‘Action Description Encoding and Consensus’ |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
|``8`` |``valueBalanceOrchard`` |``int64`` |The net value of Orchard spends minus outputs |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
|``32`` |``anchorOrchard`` |``byte[32]`` |A root of the Orchard note commitment tree at some block |
| | | |height in the past |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
|``2208 * nOrchardActions`` |``zkproofsOrchard`` |``byte[2208 * nOrchardActions]`` |Encodings of the zk-SNARK proofs for each OrchardAction |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
|``64 * nOrchardActions`` |``spendAuthSigsOrchard`` |``byte[64 * nOrchardActions]`` |Authorizing signatures for each OrchardAction |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
|``64`` |``bindingSigOrchard`` |``byte[64]`` |An Orchard binding signature on the SIGHASH transaction hash|
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
* The valueBalanceSapling , anchorSapling , and bindingSigSapling fields are present if
and only if nSaplingSpends + nSaplingOutputs > 0. If valueBalanceSapling is not present,
then valueBalanceSapling is defined to be 0.
* The valueBalanceOrchard , anchorOrchard , and bindingSigOrchard fields are present if
and only if nOrchardActions > 0. If valueBalanceOrchard is not present, then valueBalanceOrchard is
defined to be 0.
* The joinSplitPubKey and joinSplitSig fields are present if and only if nJoinSplit > 0.
Separate Sapling effecting data from authorizing data in the transaction format. This change restructures the wire format of Sapling spend and output descriptions to segregate authorizing data from the data describing the effects of the transaction in a similar fashion as has been done for Orchard. The result is now symmetric between Sapling and Orchard, and also simplifies slightly the description of the computation of the authorizing data commitment in ZIP 244.
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* The elements of ``zkproofsSaplingSpend`` and ``spendAuthSigsSapling`` have a 1:1
correspondence to the elements of ``vSaplingSpends`` and must be ordered such that
the proof or signature at a given index corresponds to the ``SaplingSpendNU5`` at
the same index.
* The elements of ``zkproofsSaplingOutput`` have a 1:1 correspondence to the elements of
``vSaplingOutputs`` and must be ordered such that the proof at a given index corresponds
to the ``SaplingOutputNU5`` at the same index.
Draft of ZIP 225
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* The elements of ``zkProofsOrchard`` and ``spendAuthSigsOrchard`` have a 1:1
correspondence to the elements of ``vOrchardActions`` and must be ordered such that
the proof or signature at a given index corresponds to the ``OrchardAction`` at
the same index.
Separate Sapling effecting data from authorizing data in the transaction format. This change restructures the wire format of Sapling spend and output descriptions to segregate authorizing data from the data describing the effects of the transaction in a similar fashion as has been done for Orchard. The result is now symmetric between Sapling and Orchard, and also simplifies slightly the description of the computation of the authorizing data commitment in ZIP 244.
2021-03-01 09:55:11 -08:00
The encodings of ``tx_in``, ``tx_out``, and ``JSDescriptionGroth16``, are as in NU4
[#protocol_nu4]_. The encodings of ``SaplingSpendNU5``, ``SaplingOutputNU5`` and
``OrchardAction`` are described below. The encoding of Sapling spends and outputs has
changed relative to prior versions in order to better separate data that describe
the effects of the transaction from the proofs of and commitments to those effects,
and for symmetry with this separation the Orchard-related section of the transaction
format.
Sapling Spend Description
--------------------------
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
| Bytes | Name | Data Type | Description |
+=============================+==========================+======================================+============================================================+
|``32`` |``cv`` |``byte[32]`` |A value commitment to the net value of the input note. |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
|``32`` |``nullifier`` |``byte[32]`` |The nullifier of the input note. |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
|``32`` |``rk`` |``byte[32]`` |The randomized validating key for the element of |
| | | |spendAuthSigsSapling corresponding to this spend. |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
The encodings of each of these elements are defined in § 7.3 ‘Spend Description Encoding
and Consensus’ of version 2021.1.16 of the Zcash Protocol Specification [#protocol_nu5]_.
Sapling Output Description
--------------------------
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
| Bytes | Name | Data Type | Description |
+=============================+==========================+======================================+============================================================+
|``32`` |``cv`` |``byte[32]`` |A value commitment to the net value of the output note. |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
|``32`` |``cmu`` |``byte[32]`` |The u-coordinate of the note commitment for the output note |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
|``32`` |``ephemeralKey`` |``byte[32]`` |An encoding of an ephemeral Jubjub public key |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
|``580`` |``encCiphertext`` |``byte[580]`` |The encrypted contents of the note plaintext. |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
|``80`` |``outCiphertext`` |``byte[580]`` |The encrypted contents of the byte string created by |
| | | |concatenation of the transmission key with the ephemeral |
| | | |secret key. |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
The encodings of each of these elements are defined in § 7.4 ‘Output Description Encoding
and Consensus’ of version 2021.1.16 of the Zcash Protocol Specification [#protocol_nu5]_.
Draft of ZIP 225
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Orchard Action Description
--------------------------
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
| Bytes | Name | Data Type | Description |
+=============================+==========================+======================================+============================================================+
|``32`` |``cv`` |``byte[32]`` |A value commitment to the net value of the input note minus |
| | | |the output note. |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
|``32`` |``nullifier`` |``byte[32]`` |The nullifier of the input note. |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
|``32`` |``rk`` |``byte[32]`` |The randomized validating key for the element of |
| | | |spendAuthSigsOrchard corresponding to this action. |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
Separate Sapling effecting data from authorizing data in the transaction format. This change restructures the wire format of Sapling spend and output descriptions to segregate authorizing data from the data describing the effects of the transaction in a similar fashion as has been done for Orchard. The result is now symmetric between Sapling and Orchard, and also simplifies slightly the description of the computation of the authorizing data commitment in ZIP 244.
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|``32`` |``cmx`` |``byte[32]`` |The x-coordinate of the note commitment for the output note |
Draft of ZIP 225
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+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
|``32`` |``ephemeralKey`` |``byte[32]`` |An encoding of an ephemeral Pallas public key |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
|``580`` |``encCiphertext`` |``byte[580]`` |The encrypted contents of the note plaintext. |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
|``80`` |``outCiphertext`` |``byte[580]`` |The encrypted contents of the byte string created by |
| | | |concatenation of the transmission key with the ephemeral |
| | | |secret key. |
+-----------------------------+--------------------------+--------------------------------------+------------------------------------------------------------+
The encodings of each of these elements are defined in § 7.5 ‘Action Description Encoding
and Consensus’ of version 2021.1.16 of the Zcash Protocol Specification [#protocol_nu5]_.
Modifications to ZIP 244
========================
TxId Digest
-----------
The tree of hashes defined by ZIP 244 [#zip-0244]_ is re-structured to include a new
branch for Orchard hashes. The ``orchard_digest`` branch is the only new addition to the
tree; ``header_digest``, ``transparent_digest``, ``sprout_digest``, and ``sapling_digest``
are as in ZIP 244::
txid_digest
├── header_digest
├── transparent_digest
├── sprout_digest
├── sapling_digest
└── orchard_digest
txid_digest
```````````
The top hash of the ``txid_digest`` tree is modified from the ZIP 244 structure
to be a BLAKE2b-256 hash of the following values ::
T.1: header_digest (32-byte hash output)
T.2: transparent_digest (32-byte hash output)
T.3: sprout_digest (32-byte hash output)
T.4: sapling_digest (32-byte hash output)
T.5: orchard_digest (32-byte hash output)
The personalization field of this hash is unmodified from ZIP 244.
2: ``orchard_digest``
'''''''''''''''''''''
A BLAKE2b-256 hash of the following values ::
T.5c: anchorOrchard (32 bytes)
T.5b: orchard_actions_compact_digest (32-byte hash output)
T.5c: orchard_actions_memos_digest (32-byte hash output)
T.5d: orchard_actions_noncompact_digest (32-byte hash output)
T.5e: valueBalanceOrchard (64-bit signed little-endian)
The personalization field of this hash is set to::
"ZTxIdOrchardHash"
T.5b: orchard_actions_compact_digest
....................................
A BLAKE2b-256 hash of the subset of Orchard action information intended to be included in
an updated version of the ZIP-307 [#zip-0307]_ ``CompactBlock`` format for all Orchard
actions belonging to the transaction. For each action, the following elements are included
in the hash::
T.5b.i : nullifier (field encoding bytes)
Separate Sapling effecting data from authorizing data in the transaction format. This change restructures the wire format of Sapling spend and output descriptions to segregate authorizing data from the data describing the effects of the transaction in a similar fashion as has been done for Orchard. The result is now symmetric between Sapling and Orchard, and also simplifies slightly the description of the computation of the authorizing data commitment in ZIP 244.
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T.5b.ii : cmx (field encoding bytes)
Draft of ZIP 225
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T.5b.iii: ephemeralKey (field encoding bytes)
T.5b.iv : encCiphertext[..52] (First 52 bytes of field encoding)
The personalization field of this hash is set to::
"ZTxIdOrcOutCHash"
T.5c: orchard_actions_memos_digest
..................................
A BLAKE2b-256 hash of the subset of Orchard shielded memo field data for all Orchard
actions belonging to the transaction. For each action, the following elements are included
in the hash::
T.5c.i: encCiphertext[52..564] (contents of the encrypted memo field)
The personalization field of this hash is set to::
"ZTxIdOrcOutMHash"
T.5d: orchard_actions_noncompact_digest
.......................................
A BLAKE2b-256 hash of the remaining subset of Orchard action information **not** intended
for inclusion in an updated version of the the ZIP 307 [#zip-0307]_ ``CompactBlock``
format, for all Orchard actions belonging to the transaction. For each action,
the following elements are included in the hash::
T.5d.i : cv (field encoding bytes)
T.5d.ii : rk (field encoding bytes)
T.5d.iii: encCiphertext[564..] (post-memo suffix of field encoding)
T.5d.iv : outCiphertext (field encoding bytes)
The personalization field of this hash is set to::
"ZTxIdOrcOutNHash" (2 underscore characters)
Signature Digest
----------------
The signature digest creation algorithm defined by ZIP 244 [#zip-0244]_ is modified to
include a new branch for Orchard hashes. The ``orchard_digest`` branch is the only new addition
to the tree; ``header_digest``, ``transparent_digest``, ``sprout_digest``, and
``sapling_digest`` are as in ZIP 244::
signature_digest
├── header_digest
├── transparent_digest
├── sprout_digest
├── sapling_digest
└── orchard_digest
signature_digest
````````````````
A BLAKE2b-256 hash of the following values ::
S.1: header_digest (32-byte hash output)
S.2: transparent_digest (32-byte hash output)
S.3: sprout_digest (32-byte hash output)
S.4: sapling_digest (32-byte hash output)
S.5: orchard_digest (32-byte hash output)
The personalization field of this hash is unmodified from ZIP 244
S.5: orchard_digest
'''''''''''''''''''
Identical to that specified for the transaction identifier.
Authorizing Data Commitment
---------------------------
The tree of hashes defined by ZIP 244 [#zip-0244]_ for authorizing data commitments is
re-structured to include a new branch for Orchard actions. The ``orchard_digest`` branch
Separate Sapling effecting data from authorizing data in the transaction format. This change restructures the wire format of Sapling spend and output descriptions to segregate authorizing data from the data describing the effects of the transaction in a similar fashion as has been done for Orchard. The result is now symmetric between Sapling and Orchard, and also simplifies slightly the description of the computation of the authorizing data commitment in ZIP 244.
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is the only new addition to the tree; ``transparent_digest``, and ``sprout_digest``
Draft of ZIP 225
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``sapling_digest`` are as in ZIP 244::
auth_digest
├── transparent_scripts_digest
├── sprout_auth_digest
├── sapling_auth_digest
└── orchard_auth_digest
auth_digest
```````````
The tree of hashes defined by ZIP 244 [#zip-0244]_ for authorizing data commitments is
re-structured to include a new branch for Orchard authorizing data. The
``orchard_auth_digest`` branch is the only new addition to the tree;
``transparent_auth_digest``, ``sprout_auth_digest``, and ``sapling_auth_digest`` are as in
ZIP 244::
A.1: transparent_scripts_digest (32-byte hash output)
A.2: sprout_auth_digest (32-byte hash output)
A.3: sapling_auth_digest (32-byte hash output)
A.4: orchard_auth_digest (32-byte hash output)
The personalization field of this hash is unmodified from ZIP 244.
A.4: orchard_auth_digest
````````````````````````
A BLAKE2b-256 hash of the field encoding of the ``zkProofsOrchard``,
``spendAuthSigsOrchard``, and ``bindingSigOrchard`` fields of the transaction::
A.4a: zkproofsOrchard (field encoding bytes)
A.4b: spendAuthSigsOrchard (field encoding bytes)
A.4c: bindingSigOrchard (field encoding bytes)
The personalization field of this hash is set to::
"ZTxAuthOrchaHash"
Reference implementation
========================
TBD
References
==========
.. [#RFC2119] `RFC 2119: Key words for use in RFCs to Indicate Requirement Levels <https://www.rfc-editor.org/rfc/rfc2119.html>`_
.. [#protocol_nu4] `Zcash Protocol Specification, Version 2020.1.15 <protocol/protocol.pdf>`_
.. [#protocol_nu5] `Zcash Protocol Specification, Version 2021.1.16 or later <protocol/orchard.pdf>`_
.. [#zip-0244] `ZIP 244: Transaction Identifier Non-Malleability<zip-0244.rst>`_
.. [#zip-0307] `ZIP 307: Light Client Protocol for Payment Detection <zip-0307.rst>`_