Suggestion for "[ZIP 248]: Define a forward-compatible, extensible transaction format. #1156" by arya2 · Pull Request #1253 · zcash/zips

arya2 · 2026-04-04T01:44:47Z

Structured digest approach

This PR uses structured per-bundle digest trees for the transaction
identifier and authorizing data commitment. Each bundle type's defining
ZIP specifies its own digest algorithm, which SHOULD separate compact
data (for the light wallet protocol) from non-compact data to enable
trustless partial verification.

For bundle types a wallet does not understand, the wallet needs the
32-byte bundle_effects_digest to be supplied externally (e.g. by a
light wallet server or full node that implements the bundle type's
digest algorithm).

An alternative approach using flat hashes with a compact/noncompact
wire format split is proposed in #1260. That approach allows any
wallet to compute the txid without understanding all bundle types, at
the cost of requiring existing bundle types to switch from structured
to flat effect digests.

Changes in this update

Add Parsing Rules section consolidating parser-level invariants
Restructure Consensus Rules into bundle-local and cross-bundle subsections
Clarify anchorSapling handling at T.3.2c when nSpendsSapling = 0
Pad ZTxIdEffBndHash / ZTxAuthBndHash personalizations to 16 characters
Fix heading underline in Per-Signature Structures
Fix typos, RST syntax, and normative language (MUST)
Remove redundant normative constraints; cross-reference Parsing Rules
Specify key comparison for mValuePoolDeltas ordering
Define transparent bundle value pool delta computation
Clarify structured digest approach for bundle type registration

Ref impl: zcash/librustzcash@main...zip248

daira · 2026-04-07T20:30:03Z

      \forall \mathsf{a}. \sum_{\mathsf{d} \in \mathsf{mValuePoolDeltas} | \mathsf{AssetUuid}(\mathsf{d}) = \mathsf{a}} \mathsf{d.value} = 0

+Sighash Versioning
+-------------------


Suggested change

-------------------

------------------

nuttycom · 2026-04-07T20:36:07Z

+--------------------+-------------------------------------------------------+
+|                    |:math:`\hspace{4.5em}` ``associatedData``              |
+--------------------+-------------+-------------+-------------+-------------+
+| ``sighashVersion`` | Transparent |   Sapling   |   Orchard   |  Issuance   |


Issuance doesn't belong here. Also, this table seems like it might be malformed given the extensible nature of this transaction format.

nuttycom · 2026-04-07T21:29:25Z

+Sighash version information is present alongside each signature in the
+authorizing data of the transaction, via the per-signature structures defined
+below.
+


The process for introducing a new sighash version (including how that affects each bundle type) should be specified here. Add a TODO.

arya2 · 2026-04-10T22:29:01Z

+* For coinbase transactions, the ``enableSpendsOrchard`` bit of the Orchard
+  bundle's ``flagsOrchard`` field MUST be 0.


Do we want to make this a global rule in the protocol instead of applying it to V5 txs there and writing it again here?

arya2 · 2026-04-14T20:45:07Z

+   identifier, if effecting data is present. For bundle types not defined in
+   this ZIP, the ``bundle_effects_digest`` MUST be equal to
+   ``BLAKE2b-256(personalization, vBundleData)`` where
+   ``personalization`` is the `Opaque Effects Personalization`_ for the
+   bundle's ``(bundleType, bundleVariant)`` pair. This ensures that wallets
+   which do not understand the bundle type can still compute the correct
+   transaction identifier by hashing the raw effecting data.


@nuttycom did you have an argument against using flat hashes everywhere for computing transaction ids from effects/auth bundles? I've mixed legacy structured hashes and flat hashes here, but would like to update it to use flat hashes everywhere if there are no objections.

- Register ZSA Issuance bundle type in the V6 bundle registry - Update digest section to reference effects_bundles_digest and auth_bundles_digest - Add reference to extensible transaction format ZIP - Remove unused ZIP 244 and ZIP 246 references Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

- Register OrchardZSA bundle type in the V6 bundle registry - Update digest section to reference effects_bundles_digest and auth_bundles_digest - Add reference to extensible transaction format ZIP - Remove unused ZIP 244 and ZIP 246 references Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

…uples. This makes the mutual exclusivity of bundle variants (e.g. Orchard vs OrchardZSA) implicit in the map structure, and allows clients that do not recognize a specific bundleVersion to still identify which pool is affected. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Add a section to ZIP 248 describing wallet requirements for handling unknown bundle types and versions. Update ZIP 226 to reference ZIP 248 instead of ZIP 230 for transaction format and wallet implications. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

…ation. Make explicit that each new bundle type's defining ZIP specifies its own digest algorithm (point 7 of Bundle Type Registration), SHOULD use a structured sub-tree separating compact from non-compact data for trustless partial verification, and that wallets unable to compute the digest themselves may obtain it from any source that implements the algorithm (e.g. a light wallet server or full node). Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

daira changed the base branch from main to draft/extensible_tx_format April 7, 2026 20:09

nuttycom reviewed Apr 7, 2026

View reviewed changes

Comment thread zips/zip-0248.rst Outdated

daira reviewed Apr 7, 2026

View reviewed changes

Comment thread zips/zip-0248.rst Outdated

daira reviewed Apr 7, 2026

View reviewed changes

nuttycom reviewed Apr 7, 2026

View reviewed changes

daira force-pushed the suggestion-extensible_tx_format branch from 3b9fefb to b1a46d8 Compare April 9, 2026 04:24

daira changed the base branch from draft/extensible_tx_format to main April 9, 2026 04:25

daira marked this pull request as draft April 9, 2026 04:31

daira force-pushed the suggestion-extensible_tx_format branch from b1a46d8 to b31e49d Compare April 9, 2026 04:36

arya2 commented Apr 10, 2026

View reviewed changes

arya2 commented Apr 14, 2026

View reviewed changes

daira force-pushed the suggestion-extensible_tx_format branch from cf2a3f6 to ab81ac2 Compare April 15, 2026 00:26

daira mentioned this pull request Apr 15, 2026

[ZIP 248]: Alternative — flat effect digests with compact/noncompact wire split #1260

Open

nuttycom force-pushed the suggestion-extensible_tx_format branch from ab81ac2 to de8b429 Compare April 21, 2026 20:28

nuttycom changed the base branch from main to draft/extensible_tx_format April 21, 2026 20:28

daira added the F-transaction-v6 Feature: v6 transactions label Apr 24, 2026

nuttycom force-pushed the draft/extensible_tx_format branch from 1e02d2f to 5c49035 Compare May 13, 2026 18:44

nuttycom force-pushed the draft/extensible_tx_format branch 2 times, most recently from b64bf8f to 0f0ffe1 Compare September 1, 2026 18:22

nuttycom and others added 6 commits September 1, 2026 14:53

[ZIP 248]: Rename bundleVersion to bundleVariant

7f0c583

arya2 force-pushed the suggestion-extensible_tx_format branch from de8b429 to 4186266 Compare September 1, 2026 19:17

nuttycom force-pushed the draft/extensible_tx_format branch 2 times, most recently from 4ad4038 to 873532a Compare September 1, 2026 23:57

Navigation Menu

Uh oh!

Suggestion for "[ZIP 248]: Define a forward-compatible, extensible transaction format. #1156" - #1253

Suggestion for "[ZIP 248]: Define a forward-compatible, extensible transaction format. #1156"#1253
arya2 wants to merge 6 commits into
draft/extensible_tx_formatfrom
suggestion-extensible_tx_format

arya2 commented Apr 4, 2026 •

edited by nuttycom

Loading

Uh oh!

Uh oh!

Uh oh!

daira Apr 7, 2026

Uh oh!

nuttycom Apr 7, 2026

Uh oh!

nuttycom Apr 7, 2026

Uh oh!

arya2 Apr 10, 2026

Uh oh!

arya2 Apr 14, 2026 •

edited

Loading

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

		* For coinbase transactions, the ``enableSpendsOrchard`` bit of the Orchard
		bundle's ``flagsOrchard`` field MUST be 0.

Uh oh!

Conversation

arya2 commented Apr 4, 2026 • edited by nuttycom Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Structured digest approach

Changes in this update

Uh oh!

Uh oh!

Uh oh!

daira Apr 7, 2026

Choose a reason for hiding this comment

Uh oh!

nuttycom Apr 7, 2026

Choose a reason for hiding this comment

Uh oh!

nuttycom Apr 7, 2026

Choose a reason for hiding this comment

Uh oh!

arya2 Apr 10, 2026

Choose a reason for hiding this comment

Uh oh!

arya2 Apr 14, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

arya2 commented Apr 4, 2026 •

edited by nuttycom

Loading

arya2 Apr 14, 2026 •

edited

Loading