morphit/docs/adr/0031-zcash-addition.md

ADR-0031: Zcash (ZEC) Addition — Trade-Only with Per-Address Privacy Choice

Status: Accepted (Part 122 cp39, 2026-05-19)

Context:

Following Dogecoin (ADR-0030), Dash (ADR-0027), Litecoin (cp24), Bitcoin Cash (cp21), DAI (ADR-0029), USDC (ADR-0028), USDT (Part 121), BLURT/BTC/XMR (founders' tradeable set), Morphit adds Zcash (ZEC) as the eleventh tradable asset. ZEC is a proof-of-work cryptocurrency launched in 2016 as the first practical deployment of zero-knowledge proofs (zk-SNARKs) in a cryptocurrency. The protocol supports two address families that coexist on the same chain:

• Transparent addresses (t1 / t3, base58, ~35 chars) — publicly visible amounts and parties, similar in shape to Bitcoin's legacy addresses.
• Shielded addresses (zs1 Sapling, u1 Unified Address bundling Orchard receivers) — sender, recipient, and amount hidden on chain via zero-knowledge proofs.

Per-trade, each participant picks the address type that matches their preferred posture. Both are first-class on the protocol.

Decision

1. ZEC is a Category-B trade-only asset

Per Memory #23 the fee_method enum stays frozen at {blurt, btc, xmr, waived_first_buy}. ZEC therefore ships with canBeTraded: true and canPayListingFee: false, matching the BCH/LTC/DASH/DOGE/USDT/USDC/DAI pattern.

2. Single-network mainnet

ZEC supports testnet and regtest for development but the only canonical home for the asset on Morphit is mainnet. No network picker is mounted in the post-order form or address-share modal.

3. Address regex covers all four formats

The canonical registry's addressShape regex accepts all four protocol-valid address types:

^(t[13][1-9A-HJ-NP-Za-km-z]{33}|zs1[02-9ac-hj-np-z]{75}|u1[02-9ac-hj-np-z]{30,300})$

• t1/t3 transparent: base58 alphabet, 33 chars after the prefix.
• zs1 Sapling shielded: bech32 alphabet (excluding 1, b, i, o per Bech32 spec), exactly 75 data chars after the zs1 prefix.
• u1 Unified Address: bech32m alphabet, variable length (typically 90–300 chars depending on whether transparent, Sapling, and/or Orchard receivers are bundled).

The frontend mirror's validateZec splits the union into three named regexes (ZEC_T_RE, ZEC_ZS_RE, ZEC_U_RE) for clearer error reporting and test coverage. Permissive shape check; chain-binding happens on the receiving wallet side.

4. Chat-link explorer default — mainnet.zcashexplorer.app

The operator surveyed 7 candidate explorers at addition time. The bundled default is mainnet.zcashexplorer.app — community-run, project-aligned, no third-party tracking, supports both transparent and shielded transaction lookups by txid. Same privacy/decentralization rationale as insight.dash.org for DASH and blockstream.info for BTC: prefer a project-aligned or community-run explorer over third-party aggregators or exchange-affiliated services. Operators wanting a different default override via MORPHIT_FRONTEND_ZEC_CHAT_LINK_URL.

Full survey:

Explorer	Disposition	Rationale
mainnet.zcashexplorer.app	Chosen	Community-run, project-aligned, no third-party tracking
blockchair.com/zcash	Available	Third-party aggregator; already used for DOGE so operators preferring CSP-origin consolidation can choose this
zcashinfo.com	Available	Community-run; lower traffic; secondary recommendation
3xpl.com/zcash	Available	Third-party aggregator; less focused
blockexplorer.one/zcash/mainnet	Available	Generic multi-chain aggregator
zcash.tokenview.io	Available	Tokenview multi-chain; vendor-hosted
cipherscan.app	Available	Newer privacy-focused explorer; smaller community footprint at launch

5. Universal no-favoritism principle for privacy-coin framing

Adopted as a same-checkpoint design principle for all privacy-relevant assets on Morphit:

Morphit never ranks privacy approaches across assets or implies one privacy coin is "the most private." Each privacy-focused chain gets respectful framing describing what it is (its privacy technology, address types, and trade-offs) without comparative claims that one is stronger than another. This avoids tribal in-fighting between privacy-coin communities and respects each user's free choice of which chain matches their priorities.

This is universal — it applies to ZEC, XMR, DASH, DOGE, BTC, BCH, LTC, BLURT, and any future privacy-relevant addition. The principle replaces previously-shipped language like "For Morphit's strongest privacy posture, use XMR" with neutral descriptions of each chain's privacy properties. Cleaned at cp39 across:

• Canonical asset-registry comments (DASH and DOGE entries).
• Frontend asset-registry comments (LTC, DASH, and DOGE entries).
• Privacy-guide i18n strings × 10 locales (privacy.guides.xmr.intro, privacy.guides.dash.caveats, privacy.guides.doge.caveats).
• FAQ string faq.entries.what_is_doge.a × 10 locales.
• DOGE smoke source docblock.

6. Privacy framework — optInPrivacyTech: ['shielded-pools']

Zcash's privacy mechanism is per-address: shielded addresses (zs1/u1) use zk-SNARKs to hide sender, recipient, and amount; transparent addresses (t1/t3) reveal them. The privacyFeatures struct registers 'shielded-pools' as the opt-in tech tag and privacyGuideKey: 'zec' points at the /privacy/zec guide page (registry-driven; the [asset] dynamic route auto-renders).

The privacy-guide content describes the difference between shielded-to-shielded (both sides hidden), mixed (one side revealed), and transparent-to-transparent (both revealed) transactions, plus wallet-support notes (Zashi, Zecwallet, Nighthawk).

7. zcash: URI scheme (ZIP-321)

The payment-URI builder emits zcash:<address>?amount=<decimal> per ZIP-321. ZEC addresses are unambiguous within the URI scheme: the four prefixes (t1/t3/zs1/u1) disambiguate transparent versus shielded receiver intent.

8. Decimals = 8

ZEC uses 8 decimals (zatoshi = 10⁻⁸ ZEC), matching the BTC family's smallest-unit semantics. Amount-jitter routes through jitterUtxoAmount (same as BTC/BCH/LTC/DASH/DOGE).

9. Brand color text-yellow-400

Distinct from DOGE's text-yellow-500 and USDT's text-amber-400 and the other 8 accent colors. Yellow-400 lands the Zcash gold brand color (#F2B525) within Tailwind's palette without colliding with existing assignments.

Consequences

• ZEC is enabled by default on every fresh Morphit instance. Operators preferring not to support ZEC can disable via MORPHIT_INDEXER_DISABLED_ASSETS="ZEC" (or any longer list including ZEC).
• The frozen fee_method enum is unaffected. Listing fees stay BLURT/BTC/XMR.
• Per-address privacy choice means Morphit users will sometimes receive ZEC at transparent addresses and sometimes at shielded addresses. The chat-link explorer renders txids the same for both — the txid is canonical even when sender/recipient/amount are hidden inside the shielded payload.
• No favoritism re-introduction guard: future asset additions must follow the §5 principle. The DOGE smoke docblock (cleaned at cp39) is the template for how registry-comments and smoke source should describe each privacy chain — factually, without comparative ranking.

References

• ADR-0026 (Transparent-chain privacy framework — established the privacyFeatures struct).
• ADR-0027 (Dash addition — first chain with opt-in mixing).
• ADR-0030 (Dogecoin addition — single-network template that ZEC mirrors).
• ZIP-321 (Payment Request URI specification) — https://zips.z.cash/zip-0321
• Zcash protocol specification — https://zips.z.cash/protocol/protocol.pdf
• Memory #23 (fee_method enum frozen at BLURT/BTC/XMR).
• Memory #29 (NEW-asset i18n native-en/es/fr/de + EN-fallback for it/pl/ru/fa/zh-CN/zh-HK).
• Cp32 LL #36 (payment-rail axis same-turn discipline).
• Cp33 CODE-3 (atomically widen all 4 wire-format gates).