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Layer 4 · DIG CAT payment & pricing

Canonical reference: chip35_dl_coin::dig (the canonical builder); digstore-chain::dig / ::cat (the byte-mirror). Builds the per-capsule $DIG payment that rides with a root-advance.

Byte-identical constants (asserted in tests on both sides)​

ConstantValueReference
DIG_ASSET_ID (TAIL hash, mainnet)a406d3a9de984d03c9591c10d917593b434d5263cabe2b42f6b367df16832f81dig.rs:43
DIG_TREASURY_INNER_PUZZLE_HASHec7c304708c7d59c078d5ae098d0dea004decf47fa1cafebb266c10ad6466ce8dig.rs:56
DIG decimals3 (1 DIG = 1000 base units)mirror dig.rs:13

The treasury inner ph decodes from xch1a37rq3cgcl2ecpudttsf35x75qzdan68lgw2l6ajvmqs44jxdn5qv6pk3y.

The payment builder​

build_dig_store_payment(buyer_synth_key, dig_cats: Vec<Cat>, store_id, amount) -> Vec<CoinSpend>
  1. Validate every dig_cat's asset id == DIG_ASSET_ID.
  2. Ring-spend the DIG CATs (lead carries the CREATE_COINs; the rest emit assert_concurrent_spend(lead)).
  3. Create one DIG-CAT coin of amount to DIG_TREASURY_INNER_PUZZLE_HASH, carrying memos [treasury_inner_ph (hint), store_id].
  4. Return change to the buyer (hinted).
  5. Reserve no XCH — the ring nets to zero; the XCH network fee rides separately (add_fee).

(chip35 dig.rs:84. The mirror's build_dig_payment uses the chia-wallet-sdk Action/Spends system but produces the same shape — cat.rs:208-281.)

Dynamic, USD-pegged pricing — no protocol constant​

amount is a dynamic input: dig_amount = target_usd / live_DIG_price, where target_usd ≈ $1/capsule/year of realistic AWS hosting. The amount is uniform per fixed-size capsule (the 128 MiB fixed module) so price leaks nothing about content. chip35 has no hardcoded amount — the caller computes it.

Off-chain pricing

Per-capsule pricing is enforced off-chain (the hub/anchor-watcher reconciles a confirmed treasury payment); it is not a protocol constant. The mirror's COMMIT_DIG = 100_000 base units (100 DIG) is only a deterministic CLI fallback when no explicit amount is passed (anchor/dig.rs:28-41).

The commit bundle is a client-side all-or-nothing bundle

The commit bundle (the root-advance singleton spend + the DIG-CAT payment) is concatenated and co-signed all-or-nothing by the client. The payment-to-root-advance coupling is a client-side bundling convention; settlement is reconciled off-chain by the hub/anchor-watcher against a confirmed treasury payment.

Receipt verification​

dig_treasury_payment_coin(lead_dig_cat, amount) returns the CAT-wrapped treasury coin for receipt verification; cat_puzzle_hash(owner_ph, asset_id) = CatArgs::curry_tree_hash(asset_id, owner_ph); reconstruct_cat_coins walks coinset to confirm a payment landed (dig.rs:149, mirror cat.rs:39-48,85).