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Commit funds to a Head

In order to transact inside of a Head on L2, users need to have some funds available to spend. In addition to public key outputs users can also directly commit script outputs to a Head in order to accomodate different use cases.

Depending on when a commit should happens we can distinguish two types of commits:

  • Before the head is open: Commit
  • When the head is already open: Incremental commit

Both types of commits share the same API of requesting a transaction via POST /commit where the only difference is the returned transaction being either a commitTx or depositTx in the L1 protocol. See protocol or specification for more details.

Depending on what is to be committed, a user needs to decide between a simple or blueprint commit request:

  • Simple request to commit a public key output to a Head in which case they only need to show the JSON representation of the UTxO they want to spend. The returned transaction then needs to be signed by the correct private key to prove ownership.

  • Blueprint requests allow to provide a blueprint transaction together with the UTxO it spends to be able to have more fine grained control over the created commit/deposit transaction. This is crucial when comitting script UTxO where more control over some of the transaction attributes is needed (redeemers, reference inputs, validity bounds, etc.).

info

Note that blueprint transaction outputs are ignored as all the value will be locked into the Hydra L1 scripts (commit or deposit validators).

danger

TODO: Add section aboue why the design is this way here, about how to make scripts spendable in a a Hydra head commit/deposit or link a document in the user manual, or consolidate this document further into protocol and user manual. See https://github.com/cardano-scaling/hydra/issues/1655

For concrete examples on how to use the commit API see the simple and blueprint commit how-tos in the user manual.