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CheckpointSummaryProtocol

CheckpointSummaryProtocol​

protocol CheckpointSummaryProtocol : AnyObject, Sendable

A header for a Checkpoint on the IOTA blockchain.

On the IOTA network, checkpoints define the history of the blockchain. They are quite similar to the concept of blocks used by other blockchains like Bitcoin or Ethereum. The IOTA blockchain, however, forms checkpoints after transaction execution has already happened to provide a certified history of the chain, instead of being formed before execution.

Checkpoints commit to a variety of state including but not limited to:

  • The hash of the previous checkpoint.
  • The set of transaction digests, their corresponding effects digests, as well as the set of user signatures which authorized its execution.
  • The object's produced by a transaction.
  • The set of live objects that make up the current state of the chain.
  • On epoch transitions, the next validator committee.

CheckpointSummarys themselves don't directly include all of the above information but they are the top-level type by which all the above are committed to transitively via cryptographic hashes included in the summary. CheckpointSummarys are signed and certified by a quorum of the validator committee in a given epoch in order to allow verification of the chain's state.

BCS

The BCS serialized form for this type is defined by the following ABNF:

checkpoint-summary = u64                            ; epoch
u64                            ; sequence_number
u64                            ; network_total_transactions
digest                         ; contents_digest
(option digest)                ; previous_digest
gas-cost-summary               ; epoch_rolling_gas_cost_summary
u64                            ; timestamp_ms
(vector checkpoint-commitment) ; checkpoint_commitments
(option end-of-epoch-data)     ; end_of_epoch_data
bytes                          ; version_specific_data