Deposit funds into a Head

In order to transact inside of a Head on L2, users need to have some funds available to spend. Users can deposit public key outputs or script outputs into a Head to accommodate different use cases.

All deposits use the same POST /commit API endpoint, which returns a signed deposit transaction (depositTx) to be submitted to L1. See protocol or specification for more details.

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

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

• Blueprint requests allow providing a blueprint transaction together with the UTxO it spends to have more fine-grained control over the created deposit transaction. This is necessary when depositing script UTxO where more control over transaction attributes is needed (redeemers, reference inputs, validity bounds, etc.).

info

Blueprint transaction outputs are ignored — all value is locked into the Hydra deposit validator on L1.

danger

TODO: Add section about why the design is this way here, about how to make scripts spendable in a Hydra head 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 deposit API see the simple and blueprint how-tos in the user manual.