Feature: render ZAP1 attestation memos as typed event cards #2172

What

ZAP1 is an open attestation protocol that writes structured lifecycle events to Zcash shielded memos. There are currently 5 Merkle roots anchored on mainnet, 23 leaves, and 15 event types deployed.

Zodl already decrypts and displays these memos - but they show as raw strings like ZAP1:04:f265b9a06a61b2b8.... This proposal adds formatted rendering so users see what the attestation actually means.

Before / After

The Verify link opens the proof page where anyone can independently check the Merkle path back to the Zcash anchor transaction.

Scope

Transaction detail rendering only. No send flow changes. No sync changes. No new permissions.

Detection: check if the decrypted memo string matches ^(ZAP1|NSM1):[0-9a-f]{2}:[0-9a-f]{64}$

Rendering: replace the raw string with an attestation card showing event label, short hash, copy action, and verify link.

Fallback: malformed ZAP1-like strings render as plain text (current behavior).

NSM1: is the legacy prefix - same format, accepted during decode for backward compatibility.

Integration point

The memo string is already resolved before it reaches the UI. The change is at the rendering boundary:

• TransactionDetailVM.kt lines 273-275 and 315-317: content = stringRes(memo) - intercept here
• New file Zap1MemoFormatter.kt: prefix detection + type lookup (~30 lines)
• TransactionDetailInfoMemo.kt: attestation card variant

Parser (complete, 30 lines)

object Zap1MemoFormatter {
    private val PATTERN = Regex("^(ZAP1|NSM1):([0-9a-f]{2}):([0-9a-f]{64})$")

    private val EVENTS = mapOf(
        "01" to "PROGRAM_ENTRY", "02" to "OWNERSHIP_ATTEST",
        "03" to "CONTRACT_ANCHOR", "04" to "DEPLOYMENT",
        "05" to "HOSTING_PAYMENT", "06" to "SHIELD_RENEWAL",
        "07" to "TRANSFER", "08" to "EXIT",
        "09" to "MERKLE_ROOT", "0a" to "STAKING_DEPOSIT",
        "0b" to "STAKING_WITHDRAW", "0c" to "STAKING_REWARD",
        "0d" to "GOVERNANCE_PROPOSAL", "0e" to "GOVERNANCE_VOTE",
        "0f" to "GOVERNANCE_RESULT"
    )

    fun parse(memo: String): Attestation? {
        val m = PATTERN.matchEntire(memo.trim()) ?: return null
        return Attestation(
            prefix = m.groupValues[1],
            typeHex = m.groupValues[2],
            event = EVENTS[m.groupValues[2]] ?: "TYPE_0x${m.groupValues[2]}",
            hash = m.groupValues[3]
        )
    }

    data class Attestation(
        val prefix: String,
        val typeHex: String,
        val event: String,
        val hash: String
    ) {
        val verifyUrl get() = "https://pay.frontiercompute.io/verify/$hash"
        val shortHash get() = hash.take(12) + "..."
        val isLegacy get() = prefix == "NSM1"
    }
}

No new dependencies

The parser is pure Kotlin string matching. No crate bindings, no FFI, no network calls. For projects that want deeper integration, the zcash-memo-decode Rust crate (0 dependencies) classifies all Zcash memo formats including ZAP1, ZIP 302, text, binary, and empty.

Context

• Protocol: github.com/Frontier-Compute/zap1
• Verification SDK: crates.io/crates/zap1-verify (Rust + WASM)
• JS SDK: npmjs.com/package/@frontiercompute/zap1
• Solidity verifier: github.com/Frontier-Compute/zap1-verify-sol (deployed on Sepolia, Etherscan verified)
• ZIP draft: zcash/zips PR #1243
• ZIP 302 partType request: zcash/zips #1250
• Spec: ONCHAIN_PROTOCOL.md (v3.0.0)
• Full integration roadmap: WALLET_INTEGRATION.md

Happy to open the PR if there's interest.