inputs
The inputs field lists the Cells that this transaction consumes. Each item in inputs is of type CellInput, which references a previously created output Cell.
Structure of CellInput
| Name | Type | Description |
|---|---|---|
previous_output | OutPoint | References a specific output Cell from a previous transaction. |
since | Uint64 | A condition that restricts when this input can be used. See RFC: Transaction Since Precondition for more. |
previous_output
A reference to the Cell being used as input. It consists of a transaction hash and an output index that together identify the exact output Cell.
| Name | Type | Description |
|---|---|---|
hash | H256 (hash) | Hash of the transaction that this Cell belongs to. |
index | Uint32 | Index of the Cell in its transaction's output list. |
since
The since field is an optional condition attached to each input in a transaction. It specifies a time constraint that must be met before the input becomes valid. A CKB node will only consider the input (and thus the entire transaction) valid if the current chain state meets or exceeds the since requirement.
This mechanism allows for time-locked inputs, enabling use cases like delayed payments or multi-party coordination. Transactions can include inputs from multiple parties. Each input can have its own since condition, giving each party control over when their part of the transaction becomes valid. However, if any single input’s since condition is unmet, the entire transaction will be rejected by the node.
The since value can be expressed using one of the following metrics:
- Block number
- Epoch number (with fraction)
- Timestamp
For technical details on encoding and evaluation rules, see RFC0017: Transaction Since Precondition.