Number	Category	Status	Author	Organization	Created
0013	Standards Track	Proposal	Dingwei Zhang	Nervos Foundation	2019-01-02

get_block_template

Abstract

This RFC describes the decentralized CKB mining protocol.

Motivation

The original get_work [btc eth] mining protocol simply issues block headers for a miner to solve, the miner is kept in the dark, and has no influence over block creation. get_block_template moves block creation to the miner, the entire block structure is sent, and left to the miner to (optionally) customize and assemble, miner are enabled to audit and possibly modify the block before hashing it, this improves the security of the CKB network by making blocks decentralized.

Specification

Block Template Request

A JSON-RPC method is defined, called get_block_template. It accepts exactly three argument:

Key	Required	Type	Description
cycles_limit	No	Number	maximum number of cycles to include in template
bytes_limit	No	Number	maximum number of bytes to use for the entire block
max_version	No	Number	highest block version number supported

For cycles_limit, bytes_limit and max_version, if omitted, the default limit (consensus level) is used. Servers SHOULD respect these desired maximums (if those maximums exceed consensus level limit, Servers SHOULD instead return the consensus level limit), but are NOT required to, clients SHOULD check that the returned template satisfies their requirements appropriately.

get_block_template MUST return a JSON Object containing the following keys:

Key	Required	Type	Description
version	Yes	Number	block version
difficulty	Yes	String	difficulty in hex-encoded string
current_time	Yes	Number	the current time as seen by the server (recommended for block time)
number	Yes	Number	the number of the block we are looking for
parent_hash	Yes	String	the hash of the parent block, in hex-encoded string
cycles_limit	No	Number	maximum number of cycles allowed in blocks
bytes_limit	No	Number	maximum number of bytes allowed in blocks
commit_transactions	Should	Array of Objects	objects containing information for CKB transactions (excluding cellbase)
proposal_transactions	Should	Array of String	array of hex-encoded transaction proposal_short_id
cellbase	Yes	Object	information for cellbase transaction
work_id	No	String	if provided, this value must be returned with results (see Block Submission)

Transaction Object

The Objects listed in the response's "commit_transactions" key contains these keys:

Key	Required	Type	Description
hash	Yes	String	the hash of the transaction
required	No	Boolean	if provided and true, this transaction must be in the final block
cycles	No	Number	total number of cycles, if key is not present, cycles is unknown and clients MUST NOT assume there aren't any
depends	No	Array of Numbers	other transactions before this one (by 1-based index in "transactions" list) that must be present in the final block if this one is; if key is not present, dependencies are unknown and clients MUST NOT assume there aren't any
data	Yes	String	transaction Molecule bytes in hex-encoded string

Block Submission

A JSON-RPC method is defined, called submit_block. to submit potential blocks (or shares). It accepts two arguments: the first is always a String of the hex-encoded block Molecule bytes to submit; the second is String of work_id.

Key	Required	Type	Description
data	Yes	String	block Molecule bytes in hex-encoded string
work_id	No	String	if the server provided a workid, it MUST be included with submissions

References

• bitcoin Getwork, https://en.bitcoin.it/wiki/Getwork
• ethereum Getwork, https://github.com/ethereum/wiki/wiki/JSON-RPC#eth_getwork
• Molecule Encoding