ZIP Numbering Conventions

The ZIP Editors currently use the following conventions when numbering ZIPs:

• if a ZIP directly corresponds to a BIP (Bitcoin Improvement Proposal), and the number doesn't clash, assign the same number;
• if it affects the consensus layer or the core protocol, assign a number in the range 200..299;
• if it affects only higher layers but is needed for interoperability between node implementations or other parts of the ecosystem, assign a number in the range 300..399;
• if it is specific to an implementation (e.g. zcashd or zebra), assign a number in the range 400..499;
• if it concerns Consensus Process, assign a number in the range 0..9 or above 1000;
• try to number ZIPs that should or will be deployed together consecutively (subject to the above conventions), and in a coherent reading order.

These conventions are subject to change by consensus of the ZIP Editors.

Transferring ZIP Ownership

It occasionally becomes necessary to transfer ownership of ZIPs to a new Owner. In general, we'd like to retain the original Owner as a co-Owner of the transferred ZIP, but that's really up to the original Owner. A good reason to transfer ownership is because the original Owner no longer has the time or interest in updating it or following through with the ZIP process, or has fallen off the face of the 'net (i.e. is unreachable or not responding to email). A bad reason to transfer ownership is because you don't agree with the direction of the ZIP. We try to build consensus around a ZIP, but if that's not possible, you can always submit a competing ZIP.

If you are interested in assuming ownership of a ZIP, send a message asking to take over, addressed to all of the current Owner(s) and the ZIP Editors. If the Owner(s) who are proposed to be removed don't respond in a timely manner, the ZIP Editors and any remaining current Owners will make a decision (such decisions may be reversed).

If an author of a ZIP is no longer an Owner, an Original-Authors: field SHOULD be added to the ZIP metadata indicating the original authorship (without email addresses), unless the original author(s) request otherwise.

ZIP Editors

The current ZIP Editors are:

• Jack Grigg, associated with the Electric Coin Company;
• teor, Conrado Gouvea, and Arya, associated with the Zcash Foundation.
• Aditya Bharadwaj, associated with Nighthawk Apps.

All can be reached at zips@z.cash. The current design of the ZIP Process dictates that there are always at least two ZIP Editors: at least one from the Electric Coin Company and at least one from the Zcash Foundation.

ZIP Editors MUST declare any potential or perceived conflict of interest they have relating to their responsibilities as ZIP Editors.

ZIP Editors MUST be publicly transparent about any external influence or constraints that have been placed or attempted to be placed on their actions as ZIP Editors (including from the Electric Coin Company, Zcash Foundation, or Nighthawk Apps), whether or not it affects those actions. This should not be interpreted as requiring ZIP Editors to reveal knowledge of undisclosed security vulnerabilities or mitigations.

Additional Editors may be selected, with their consent, by consensus among the current Editors.

An Editor may be removed or replaced by consensus among the current Editors. However, if the other ZIP Editors have consensus, an Editor can not prevent their own removal.

Any Editor can resign by informing the other Editors in writing.

Whenever the ZIP Editors change, the new ZIP Editors SHOULD:

• review this ZIP to make sure it reflects current practice,
• update the Owners of this ZIP,
• review access to the ZIPs repository,
• update the <zips@z.cash> email alias, and
• invite new Editors to the Zcash Community Forum, and the #zips channel on Discord.

If it has been at least 12 months since the last ZIP Editor change, the ZIP Editors SHOULD:

• review this ZIP to make sure it reflects current practice.

ZIP Editor Responsibilities

The ZIP Editors subscribe to the Zcash Community Forum.

Each new ZIP SHOULD be submitted as a "pull request" to the ZIPs git repository 9. It SHOULD NOT contain a ZIP number unless one had already been assigned by the ZIP Editors. The pull request SHOULD initially be marked as a Draft. The ZIP content SHOULD be submitted in reStructuredText 6 or Markdown 7 format. Generating HTML for a ZIP is OPTIONAL.

For each new ZIP that comes in, the ZIP Editors SHOULD:

• Read the ZIP to check if it is ready: sound and complete. The ideas must make technical sense, even if they don't seem likely to be accepted.
• Check that the title accurately describes the content.
• Ensure that the ZIP draft has been sent to the Zcash Community Forum and as a PR to the ZIPs git repository 9.
• Ensure that motivation and backward compatibility have been addressed, if applicable.
• Check that the licensing terms are acceptable for ZIPs.

Reviewing a ZIP

Any ZIP Editor can suggest changes to a ZIP. These suggestions are the opinion of the individual ZIP Editor. Any technical or process review that ZIP Editors perform is expected to be independent of their contractual or other relationships.

ZIP Owners are free to clarify, modify, or decline suggestions from ZIP Editors. If the ZIP Editors make a change to a ZIP that the Owners disagree with, then the Editors SHOULD revert the change.

Typically, the ZIP Editors suggest changes in two phases:

• content review: multiple ZIP Editors discuss the ZIP, and suggest changes to the overall content. This is a "big picture" review.
• format review: two ZIP Editors do a detailed review of the structure and format of the ZIP. This ensures the ZIP is consistent with other Zcash specifications.

If the ZIP isn't ready, the Editors will send it back to the Owners for revision, with specific instructions. This decision is made by consensus among the current Editors.

When a ZIP is ready, the ZIP Editors will:

• Ensure that a unique ZIP number has been assigned in the pull request.
• Regenerate the corresponding HTML documents, if required.
• Remove Draft status and merge the pull request.

The ZIP editors monitor ZIP changes and update ZIP headers as appropriate.

Rejecting a ZIP or update

The ZIP Editors MAY reject a new ZIP or an update to an existing ZIP, by consensus among the current Editors. Rejections can be based on any of the following reasons:

• it violates the Zcash Code of Conduct 4 ;
• it appears too unfocused or broad;
• it duplicates effort in other ZIPs without sufficient technical justification (however, alternative proposals to address similar or overlapping problems are not excluded for this reason);
• it has manifest security flaws (including being unrealistically dependent on user vigilance to avoid security weaknesses);
• it disregards compatibility with the existing Zcash blockchain or ecosystem;
• it is manifestly unimplementable;
• it includes buggy code, pseudocode, or algorithms;
• it manifestly violates common expectations of a significant portion of the Zcash community;
• it updates a ZIP's status, or fails to make a needed status update, in a way inconsistent with the requirements in Specification of Status Workflow;
• in the case of a Proposed, Active, Implemented, or Final ZIP, the update makes a substantive change to which there is significant community opposition;
• it is dependent on a patent that could potentially be an obstacle to adoption of the ZIP;
• it includes commercial advertising or spam;
• it disregards formatting rules;
• it makes non-editorial edits to previous entries in a ZIP's Change history, if there is one;
• an update to an existing ZIP extends or changes its scope to an extent that would be better handled as a separate ZIP;
• a new ZIP has a category that does not reflect its content, or an update would change a ZIP to an inappropriate category;
• it violates any specific "MUST" or "MUST NOT" rule in this document;
• the expressed political views of a Owner of the document are inimical to the Zcash Code of Conduct 4 (except in the case of an update removing that Owner);
• it is not authorized by the stated ZIP Owners;
• it removes an Owner without their consent (unless the reason for removal is directly related to a breach of the Code of Conduct by that Owner);
• it violates a conformance requirement of any Active Process ZIP (including this ZIP).

The ZIP Editors MUST NOT unreasonably deny publication of a ZIP proposal or update that does not violate any of these criteria. If they refuse a proposal or update, they MUST give an explanation of which of the criteria were violated, with the exception that spam may be deleted without an explanation.

Note that it is not the primary responsibility of the ZIP Editors to review proposals for security, correctness, or implementability.

Communicating with the ZIP Editors

Please send all ZIP-related communications either:

• by email to <zips@z.cash>,
• by opening an issue on the ZIPs issue tracker, or
• by sending a message in the #zips channel on the Zcash R&D Discord.

All communications should abide by the Zcash Code of Conduct 4 and follow the GNU Kind Communication Guidelines 5.

ZIP Editor Meeting Practices

The ZIP Editors SHOULD meet on a regular basis to review draft changes to ZIPs. Meeting times are agreed by consensus among the current ZIP Editors. A ZIP Editor meeting can be held even if some ZIP Editors are not available, but all Editors SHOULD be informed of significant decisions that are likely to be made at upcoming meetings.

The ZIP Editors will appoint a ZIP Secretary, which can be a shared or rotating role. The ZIP Secretary will:

• share a draft agenda with the ZIP Editors at least 24 hours before each ZIP Editors' meeting;
• share draft minutes of significant decisions with the ZIP Editors in the week after the ZIP Editors' meeting; and
• share significant ZIP changes, including significant changes of status (in particular, progression of a ZIP to Proposed status), on the Zcash Community Forum.

If the draft agenda is empty, any ZIP Editor MAY submit agenda items, or suggest that the meeting is cancelled.

ZIP stubs

A ZIP stub records that the ZIP Editors have reserved a number for a ZIP that is under development. It is not a ZIP, but exists in the ZIPs git repository 9 at the same path that will be used for the corresponding ZIP if and when it is published. It consists only of a preamble, which MUST use Reserved as the value of the Status field.

ZIP stubs can be added and removed, or replaced by the corresponding ZIP, at the discretion of the ZIP Editors. If a ZIP stub is removed then its number MAY be reused, possibly for an entirely different ZIP.

ZIP header preamble

Each ZIP or ZIP stub MUST begin with a RFC 822-style header preamble. For ZIPs and ZIP stubs written in reStructuredText, this is represented as :: on the first line, followed by a blank line, then the preamble indented by 2 spaces.

The following header fields are REQUIRED for ZIPs:

ZIP:
Title:
Owners:
Status:
Category:
Created:
License:

The following additional header fields are OPTIONAL for ZIPs:

Credits:
Original-Authors:
Discussions-To:
Pull-Request:
Obsoleted-By:
Updated-By:
Obsoletes:
Updates:

For ZIP stubs, only the ZIP:, Title:, Status:, and Category: fields are REQUIRED. Typically the other fields applicable to ZIP stubs are Credits:, Discussions-To: and Pull-Request:, which are OPTIONAL.

The Owners header lists the names and email addresses of all the Owners of the ZIP. The format of the Owners header value SHOULD be:

Random J. User <address@dom.ain>

If there are multiple Owners, each should be on a separate line.

Credits: and Original-Authors: fields SHOULD NOT include email addresses.

The "Owners", "Credits", and "Original-Authors" headers always use these plural spellings even there is only one Owner, one person to be credited, or one original author.

While a ZIP is in public discussions (usually during the initial Draft phase), a Discussions-To header will indicate the URL where the ZIP is being discussed. No Discussions-To header is necessary if the ZIP is being discussed privately with the Owner.

The Pull-Request header, if present, gives an URL to a Pull Request for the ZIP.

The Category header specifies the type of ZIP, as described in ZIP categories. Multiple categories MAY be specified, separated by " / ".

The Created header records the date that the ZIP was submitted. Dates should be in yyyy-mm-dd format, e.g. 2001-08-14.

For ZIPs written in reStructuredText, URLs in header fields SHOULD be surrounded by < >; this ensures that the link is rendered correctly.

Auxiliary Files

ZIPs may include auxiliary files such as diagrams. Auxiliary files should be included in a subdirectory for that ZIP; that is, for any ZIP that requires more than one file, all of the files SHOULD be in a subdirectory named zip-XXXX.

Specification of Status Workflow

Owners of a ZIP MAY decide on their own to change the status between Draft or Withdrawn. All other changes in status MUST be approved by consensus among the current ZIP Editors.

A ZIP SHOULD only change status from Draft (or Rejected) to Proposed, when the Owner deems it is complete and there is rough consensus on the forums, validated by consensus among the current ZIP Editors. If it's a Consensus ZIP, a Deployment section MUST be present in order for the ZIP to change status to Proposed. Typically, although not necessarily, this will specify a network upgrade in which the consensus change is to activate.

A ZIP's status is Released if it is Proposed, Active, Implemented, or Final (i.e. not Draft, Rejected, Obsolete, or Withdrawn).

A ZIP SHOULD NOT be changed from a non-Released status to a Released status if there is significant community opposition to its content. (However, Draft ZIPs explicitly MAY describe proposals to which there is, or could be expected, significant community opposition.)

A Released ZIP MUST NOT be changed to a non-Released status if the specification is already implemented and is in common use, or where a Process ZIP still reflects a consensus of the community.

A Standards ZIP SHOULD only change status from Proposed to Implemented once the Owners provide an associated reference implementation. For Consensus ZIPs, an implementation MUST have been merged into at least one consensus node codebase (currently zcashd and/or zebra), typically in the period after the network upgrade's specification freeze but before the implementation audit. If the Owners miss this deadline, the Editors or Owners MAY choose to update the Deployment section of the ZIP to target another upgrade, at their discretion.

A Process or Informational ZIP SHOULD change status from Proposed to Active when it achieves rough consensus on the forum or PR. Such a proposal is said to have rough consensus if it has been substantially complete and open to discussion on the forum or GitHub PR for at least one month, has been in Proposed status for at least one week, and no person maintains any unaddressed substantiated objections to it. Addressed or obstructive objections can be ignored/overruled by general agreement that they have been sufficiently addressed, but clear reasoning MUST be given in such circumstances.

When an Active, Implemented, or Final ZIP is no longer relevant –for example because its implementation has fallen out of use or its process is no longer followed– its status SHOULD be changed to Obsolete. This change MUST also be objectively verifiable and/or discussed. Final ZIPs MAY be updated; the specification is still in force but modified by another specified ZIP or ZIPs (check the optional Updated-By header).

If a non-editorial update is made to an Obsolete, Withdrawn, or Rejected ZIP, its status MUST be changed appropriately.

Recommended licenses

• MIT: Expat/MIT/X11 license
• BSD-2-Clause: OSI-approved BSD 2-clause license
• BSD-3-Clause: OSI-approved BSD 3-clause license
• CC0-1.0: Creative Commons CC0 1.0 Universal
• GNU-All-Permissive: GNU All-Permissive License
• Apache-2.0: Apache License, version 2.0

In addition, it is RECOMMENDED that literal code included in the ZIP be dual-licensed under the same license terms as the project it modifies. For example, literal code intended for zcashd would ideally be dual-licensed under the MIT license terms as well as one of the above with the rest of the ZIP text.

Not recommended, but acceptable licenses

• BSL-1.0: Boost Software License, version 1.0
• CC-BY-4.0: Creative Commons Attribution 4.0 International
• CC-BY-SA-4.0: Creative Commons Attribution-ShareAlike 4.0 International
• AGPL-3.0+: GNU Affero General Public License (AGPL), version 3 or newer
• FDL-1.3: GNU Free Documentation License, version 1.3
• GPL-2.0+: GNU General Public License (GPL), version 2 or newer
• LGPL-2.1+: GNU Lesser General Public License (LGPL), version 2.1 or newer

Not acceptable licenses

All licenses not explicitly included in the above lists are not acceptable terms and MUST NOT be used for a Zcash Improvement Proposal.

Rationale

Bitcoin's BIP 1 allowed the Open Publication License or releasing into the public domain; was this insufficient?

• The OPL is generally regarded as obsolete, and not a license suitable for new publications.
• The OPL license terms allowed for the author to prevent publication and derived works, which was widely considered inappropriate.
• In some jurisdictions, releasing a work to the public domain is not recognised as a legitimate legal action, leaving the ZIP simply copyrighted with no redistribution or modification allowed at all.

Why are there software licenses included?

• Some ZIPs, especially in the Consensus category, may include literal code in the ZIP itself which may not be available under the exact license terms of the ZIP.
• Despite this, not all software licenses would be acceptable for content included in ZIPs.