Support Dash Core v24 wire formats: CbTx v4, special tx types 10-12, ProRegTx v3, version 2 asset-unlock txid #302

What Core v24 changes on the wire

Dash Core develop (the v24 line; dashpay/dash#7437 and dashpay/dash#7639 merged Sep 18-21) introduces the following once DEPLOYMENT_V24 activates. None of it is live on mainnet or testnet yet; testnet activation is the next step, so parsers need to be ready before then.

1. CbTx version 4 (src/evo/cbtx.h:32-68). A new field merkleRootAssetUnlocks (uint256) follows creditPoolBalance. From the activation block on, every coinbase must be version 4 (src/evo/cbtx.cpp:45-51: version ≥ 4 is required when v24 is active, rejected before). The field is the merkle root over the instance hashes of the block's version-2 asset unlocks, all-zero when there are none.
2. Version 2 Asset Unlock txid (src/primitives/transaction.cpp:76-88, src/primitives/transaction.h:47-53). Payload version byte 2, serialization identical to v1, but txid = SHA256d(serialized tx with the trailing 132 bytes zeroed) — requestedHeight (4) + quorumHash (32) + quorumSig (96). The hash of the full serialization is the instance hash, used by the new inv type MSG_ASSET_UNLOCK (34, protocol 70242) and by the CbTx root above. Re-signed instances of one withdrawal therefore share a txid and their outputs are spent by that stable txid. Platform emits v1 today and will switch to v2 after activation (Emit version 2 Asset Unlock transactions once Core v24 activates (stable txid + InstantSend-locked withdrawals) platform#4908).
3. Three new special transaction types (src/primitives/transaction.h:39-41): TRANSACTION_PROVIDER_DISSOLVE = 10 (ProDisTx), TRANSACTION_PROVIDER_UPDATE_SHARE = 11 (ProUpShareTx), TRANSACTION_PROVIDER_UPDATE_SHARED_REGISTRAR = 12 (ProUpSharedRegTx). Payloads in src/evo/providertx.h (CProDisTx: nVersion u16, proTxHash, actorIndex, sig_count u8, sigs[]; CProUpShareTx: nVersion, proTxHash, shareIndex, scriptReward, inputsHash, vchSig; CProUpSharedRegTx: nVersion, proTxHash, pubKeyOperator (basic BLS), keyIDVoting, inputsHash, sig_count u8, sigs[]). Spec: docs: add Decentralized Masternode Shares DIP dips#187.
4. ProRegTx version 3 (ExtAddr) becomes valid (ProTxVersion::GetMax, src/evo/providertx.h). Its layout after nOperatorReward differs from v1/v2 (src/evo/providertx.h:162-226): nested netInfo (extended-address format instead of a single service address), then payouts_count u8 + payouts[] ({scriptPayout, reward u16}, DIP-26 multi-party payouts), shares_count u8 + shares[] ({amount i64, scriptRefund, scriptReward, keyIDOwner}), joinSigs[shares_count] (var-bytes each), nEarlyPeriodBlocks u32, nEarlyPenalty i64, then inputsHash; for Evo nodes platformNodeID follows without the P2P/HTTP port fields. scriptPayout is not serialized in v3. Same ExtAddr treatment applies to ProUpServTx/ProUpRegTx v3 where applicable.

What to check / fix in dashj (master @ 2026-09-22)

• Transaction.Type (core/src/main/java/org/bitcoinj/core/Transaction.java:102-113) maps 10 to TRANSACTION_TYPE_MAX, and 11/12 have no mapping. A ProDisTx (type 10) will be classified as TYPE_MAX; verify the unmapped values resolve to TRANSACTION_UNKNOWN rather than throwing, and add real types for 10/11/12.
• CoinbaseTx.parse() (core/src/main/java/org/bitcoinj/evolution/CoinbaseTx.java) reads through the v3 fields only and sets length = cursor - offset. Transaction keeps the raw extraPayload bytes for serialization, so the txid should survive a v4 coinbase — please confirm with a v4 coinbase vector that getTxId() and the mnlistdiff coinbase merkle proof still verify, and add merkleRootAssetUnlocks (32 bytes after creditPoolBalance) to the parser so bitcoinSerializeToStream on a modified object cannot drop it.
• ProviderRegisterTx does not implement the v3 layout (nested extended addresses, DIP-26 payouts, collateral shares, no port fields for Evo nodes).
• Transaction.getTxId() hashes the full serialization, so v2 asset unlocks get a txid Core does not use. Once Platform emits v2 withdrawals (Emit version 2 Asset Unlock transactions once Core v24 activates (stable txid + InstantSend-locked withdrawals) platform#4908), withdrawals received by the Android wallet would be recorded under the wrong txid and their outputs could not be spent. Implement: for tx type 9 with payload version ≥ 2, hash with the trailing 132 payload bytes zeroed (Core vectors in src/test/evo_assetlocks_tests.cpp).

Core references: src/evo/cbtx.h, src/evo/providertx.h, src/primitives/transaction.{h,cpp}, doc/release-notes-7437.md, doc/release-notes-7639.md.