Proof-of-Work Mining

XPower uses proof-of-work not for consensus (Avalanche handles that), but for token distribution — a provably fair mechanism where every XPOW token originates from computational work.

Hash Function

Miners compute Keccak-256 over a structured input:

$$\text{hash}=\text{Keccak256}(\text{address}\oplus \text{beneficiary}\parallel \text{blockHash}\parallel \text{data})$$

Where:

• address — the contract address (msg.sender)
• beneficiary — the recipient address chosen by the miner
• blockHash — a recently-initialized Avalanche block hash
• data — a 32-byte field containing a 256-bit nonce

The XOR operation between the contract address and the beneficiary address ties the hash to both the contract and the intended recipient, preventing cross-contract nonce reuse.

Difficulty

Difficulty is measured by the number of leading zero nibbles (4-bit hex digits) in the 256-bit hash output. Let $z$ be the count of consecutive zero nibbles from the start.

The probability of finding a valid hash with $z$ leading zeros is:

$$P(z)=\frac{1}{{16}^z}$$

z	Probability	Expected Hashes	Reward (XPOW)
1	1/16	16	$1\times {10}^{18}$
2	1/256	256	$3\times {10}^{18}$
3	1/4,096	~4K	$7\times {10}^{18}$
4	1/65,536	~66K	$15\times {10}^{18}$
5	1/1,048,576	~1M	$31\times {10}^{18}$
6	1/16,777,216	~17M	$63\times {10}^{18}$
7	1/268,435,456	~268M	$127\times {10}^{18}$
8	1/4,294,967,296	~4.3B	$255\times {10}^{18}$

Reward Formula

The XPOW reward for difficulty $z$ is:

$$R(z)=(2^z-1)\times {10}^{18}$$

This creates an exponential reward curve: doubling the difficulty doubles the number of expected hashes but slightly more than doubles the reward.

Treasury Split

Every successful mint splits the reward:

• 50% to the miner's beneficiary — the address specified in the mint call
• 50% to the MoeTreasury — funds the staking reward pool

This split ensures that even non-miners (staking participants) benefit from mining activity, aligning incentives across the ecosystem.

Expected Yield

For a uniform random nonce search, the expected XPOW per hash attempt is:

$$\mathbb{E}[R]=\sum _{z=1}^{\mathrm{\infty }}\frac{1}{{16}^z}\times (2^z-1)\times {10}^{18}\approx 0.076\times {10}^{18}\text{ per hash}$$

This means approximately 13 hash attempts per token on average, though the distribution is heavily skewed — most rewards come from low-difficulty solutions, while high-difficulty solutions are rare but lucrative.

Block Hash Intervals

Mining operates within 1-hour windows tied to Avalanche block hashes:

1. The miner calls XPower.init(blockHash) to register a block hash for mining
2. Solutions must be submitted within 3,600 seconds of init()
3. Each (beneficiary, blockHash, pairIndex) tuple can only be used once

This 1-hour window prevents pre-computation attacks — if a miner could compute nonces against arbitrary future block hashes, the proof-of-work would be meaningless. By requiring a recent on-chain block hash, every computation is tied to a specific, verified point in Avalanche's history.

Duplicate Prevention

The pairIndex field prevents replay of the same solution:

$$\text{pairIndex}=\text{keccak}(\text{nonce})\oplus \text{blockHash}$$

This XOR-based encoding creates a one-to-one mapping between nonces and block hashes per beneficiary. Once a pair is used, it's marked in contract storage and cannot be reused.