DustSpend

Represents spending a Dust token to pay transaction fees.

What is a Dust Spend? When you create a transaction, you need to pay fees. To pay fees, you "spend" a Dust token by providing:

• The old dust token's nullifier (to prevent double-spending)

• A commitment to the new dust token (the "change")

• A zero-knowledge proof that the spend is valid

• The fee amount

Dust Spend Flow:

Old Dust Token (e.g., 5 Dust)
  ↓
Spend 2 Dust for fees
  ↓
├─ Fee: 2 Dust (destroyed, goes to validators)
└─ Change: 3 Dust (new dust token, back to you)

Zero-Knowledge Proof: The proof ensures:

• You own the old dust token (know the secret key)

• The old nullifier is correctly computed

• The new commitment is correctly computed

• The fee amount is valid (old_value - new_value = fee)

• You're not creating dust out of thin air

Ledger Mapping: Mirrors the ledger's DustSpend: fee amount, spent-token nullifier, change commitment, and ZK proof.

Usage:

// Create a dust spend
val spend = wallet.createDustSpend(
    oldToken = myDustToken,
    feeAmount = BigInteger.valueOf(2_000_000), // 2 Dust
    secretKey = myDustSecretKey
)

// Include in transaction
val tx = UnshieldedTransaction(
    inputs = listOf(...),
    outputs = listOf(...),
    dustSpend = spend,  // Pay fees with this
    ttl = System.currentTimeMillis() + 60_000
)