Transaction Format

Version 6 follows the version 5 transaction format, with an Ironwood-pool bundle added after the Orchard-pool bundle. Within version 6, the Orchard-pool bundle keeps its version 5 layout but gains a new enableCrossAddress flag. See Orchard-Pool Bundle Changes in Version 6.

At the transaction ID layer, the Ironwood-pool bundle is another child in the transaction hash tree:

flowchart TD
    TxId["txid<br/>ZcashTxHash_ || consensusBranchId"]

    Header["header digest<br/>version, branch ID, lock time, expiry height"]
    Transparent["transparent digest"]
    Sapling["Sapling-pool digest"]
    Orchard["Orchard-pool bundle digest"]
    Ironwood["Ironwood-pool bundle digest"]

    TxId --> Header
    TxId --> Transparent
    TxId --> Sapling
    TxId --> Orchard
    TxId --> Ironwood

The Orchard-pool and Ironwood-pool bundle digests have the same structure. The difference is that the Ironwood-pool bundle uses its own personalization strings at each bundle-hash node:

flowchart TD
    OrchardBundle["Orchard-pool bundle digest<br/>ZTxIdOrchardH_v6"]
    IronwoodBundle["Ironwood-pool bundle digest<br/>ZTxIdIronwd_H_v6"]

    subgraph Shape["Same Orchard-protocol bundle hash shape"]
        Compact["actions compact hash<br/>nf, cmx, epk, compact ciphertext"]
        Memos["actions memo hash<br/>memo ciphertext"]
        NonCompact["actions non-compact hash<br/>cv, rk, remaining enc ciphertext, out ciphertext"]
        Flags["bundle flags"]
        Value["value balance"]
    end

    OrchardBundle --> Compact
    OrchardBundle --> Memos
    OrchardBundle --> NonCompact
    OrchardBundle --> Flags
    OrchardBundle --> Value

    IronwoodBundle -. same fields .-> Compact
    IronwoodBundle -. same fields .-> Memos
    IronwoodBundle -. same fields .-> NonCompact
    IronwoodBundle -. same fields .-> Flags
    IronwoodBundle -. same fields .-> Value

The same rule applies to authorization hashing: the Ironwood-pool bundle follows the Orchard-pool bundle authorization structure, but uses Ironwood-pool-specific personalization strings.

In version 6 the bundle anchor is excluded from the txid bundle digest shown above, and is instead committed in the authorization digest. This keeps both the txid and the signature sighash independent of the anchor, so that a spend can be signed before the anchor it is finalized against —the note-commitment-tree root— exists.