Proof-of-Work¶

Kakitu uses Proof-of-Work (PoW) as a spam prevention mechanism. Unlike Bitcoin's mining, Kakitu's PoW does not determine consensus or create new coins — it simply raises the cost of submitting large numbers of transactions.

Purpose¶

Without any cost per transaction, a malicious actor could flood the network with millions of transactions at no expense. PoW imposes a small computational cost per block, making spam attacks prohibitively expensive at scale while remaining negligible for normal use.

PoW does not affect: - Which blocks are confirmed - Transaction order - Fees (there are none)

Algorithm¶

Kakitu uses the Blake2b hash function:

Block height > 1 (all non-open blocks)¶

Find nonce such that:
blake2b(nonce || previous_block_hash) >= difficulty_threshold

Block height == 1 (open block — first on account)¶

Find nonce such that:
blake2b(nonce || account_public_key) >= difficulty_threshold

Where: - nonce is an 8-byte (64-bit) random value - || denotes concatenation - The comparison is unsigned integer comparison of the first 8 bytes of the hash

Difficulty Thresholds (Epoch v2)¶

Block Type	Threshold	Notes
Send / Change	`fffffff800000000`	Higher — these can broadcast value
Receive / Open / Epoch	`fffffe0000000000`	Lower — these can only claim

Send and change blocks require ~8× more work than receive blocks, because send blocks are the primary mechanism for potential spam.

Work Field Format¶

The work field in a block is an 8-byte (64-bit) hex-encoded nonce:

{
  "work": "2bf29ef00786a6bc"
}

Epoch Upgrades¶

Work difficulty can be upgraded via epoch blocks — special blocks signed by the network genesis account that upgrade all accounts to a new minimum difficulty. This allows the network to adjust spam resistance over time without a hard fork.

Epoch	Introduced	Change
v1	Genesis	Initial difficulty
v2	Upgrade	Differentiated send/receive thresholds

Pre-caching¶

Because generating work takes time (fractions of a second on a GPU, seconds on a CPU), work should be pre-generated for the next block as soon as the current block is confirmed.

After block H is confirmed: - Immediately generate work(H) in the background - Store it in a cache keyed by H - When the next block is needed, retrieve from cache for instant broadcast

Energy Efficiency¶

Kakitu's PoW is dramatically more energy-efficient than Proof-of-Work mining:

Work is generated once per block, not continuously
No mining race — only the block creator generates work
GPU work generation is optional and not required for normal operation
A typical send transaction requires < 0.001 kWh of energy to generate work

Adjusting Difficulty¶

Work can be generated above the minimum threshold. A higher-difficulty block is valid but not prioritized differently — there is no advantage to generating extra-hard work for transaction processing.

To generate at higher difficulty (e.g., for testing):

curl -s -d '{
  "action": "work_generate",
  "hash": "PREVIOUS_HASH",
  "difficulty": "ffffffff00000000",
  "multiplier": "8.0"
}' http://localhost:7076

The multiplier field can be used instead of specifying an absolute difficulty.