dMint Follow-up: PoW Distributed Mint (Future Work)

pyrxd 0.2.x implements the premine-at-deploy FT path. This document captures what a future PoW-capable SDK would need to implement Photonic’s full dMint protocol, and why most consumers do not require it.

What pyrxd 0.2.x implements

  • GlyphMetadata.for_dmint_ft(...) — metadata with p:[1,4] (FT + DMINT markers)

  • GlyphBuilder.prepare_ft_deploy_reveal(...) — reveal scripts for a premine-at-deploy FT: entire supply to treasury PKH at vout[0]

  • FtUtxoSet.build_transfer_tx(...) — conservation-enforcing FT transfer

  • CBOR cross-decoder tests (pyrxd encode ↔ RXinDexer reference decoder)

  • Deploy structural integration tests + VPS testmempoolaccept proof

The p:[1,4] marker tells indexers this token follows the dMint protocol. For premine-only consumers the only relevant part of that protocol is the deploy shape — a single reveal output carrying the full supply. The PoW ongoing-mint machinery is not used.

What is NOT implemented: PoW distributed mint

Photonic’s dMint protocol supports a second mode beyond premine: holders can mine new tokens by solving a PoW challenge embedded in a covenant UTXO that remains on-chain after deploy. pyrxd does not implement this.

Specifically missing:

1. Difficulty covenant UTXO

The deploy reveal would produce a second output — the “dMint covenant UTXO” — containing the mining difficulty parameters. This UTXO is spent and re-created by each minting transaction, updating the difficulty.

Radiant implementation would need:

  • A covenant script enforcing ASERT or LWMA difficulty adjustment

  • The minting tx must satisfy a hash-less-than-target check (OP_SHA256 of the minting tx’s nonce field < current target)

  • The covenant re-creates itself at the next output with updated params

2. Per-mint commit/reveal

Each minting event uses a two-tx commit/reveal (same shape as NFT minting in pyrxd today, but carrying FT outputs). The commit locks a small UTXO; the reveal spends it, proves PoW, and produces new FT outputs.

GlyphBuilder.prepare_commit and prepare_reveal handle the basic shape but don’t carry the PoW nonce or covenant interaction.

3. ASERT / LWMA difficulty adjustment

The difficulty target adjusts per-block (ASERT) or per-window (LWMA). Implementing this in a Radiant script covenant requires bignum comparison (OP_BIN2NUM, OP_DIV) — the same operations the Gravity Protocol uses for BTC header work. Feasible but non-trivial.

When premine-only is enough

A premine-only token mints the entire supply to a treasury wallet at deploy. Distribution happens via plain FT transfers (FtUtxoSet.build_transfer_tx) as the issuer hands out tokens. No post-deploy minting occurs.

The p:[1,4] marker is appropriate for premine-only deploys because:

  1. Photonic Wallet and most RXD indexers recognize it as the correct FT token class for fungible tokens with explicit supply

  2. It is forward-compatible — if a downstream consumer later needs a secondary PoW mint phase, the token ref is already correctly typed

Using p:[1] alone (plain FT, no dMint marker) also works for the premine shape. The choice between [1] and [1,4] is a downstream decision — [1,4] reads as “this token participates in the dMint protocol family even if it never uses the PoW phase,” which some indexers prefer.

Implementing PoW dMint (future contributor guide)

If a future contributor wants to add full PoW dMint support:

  1. Difficulty covenant script — model after pyrxd/gravity/covenant.py. Encode difficulty params as constructor arguments baked into bytecode. The covenant must re-create itself at output index N with updated target.

  2. Mint tx builder — new function build_mint_tx(covenant_utxo, nonce, miner_pkh, fee_sats). The nonce is a 4-byte field in the tx that the miner varies to find a valid PoW solution.

  3. Difficulty verification — OP_SHA256 of the serialized mint tx (minus nonce field) must be <= the current target. This is a script constraint enforced by the covenant, not by pyrxd.

  4. Tests — unit tests can use a trivially easy target (all-ones). VPS integration test can mine one token against the live covenant.

The Photonic Wallet TypeScript source (lib/dmint.ts) is the reference implementation. pyrxd’s cbor2-based CBOR encoding already matches Photonic’s payload format (verified by tests/test_cbor_cross_decoder.py).