Retirar tokens

Como retirar tokens do saldo disponível confidencial

Para retirar tokens do saldo disponível confidencial para o saldo público:

Crie dois proofs no lado do cliente:

Equality Proof (CiphertextCommitmentEqualityProofData): Verifica que o texto cifrado do saldo disponível restante após a retirada corresponde ao seu compromisso de Pedersen correspondente, garantindo que o novo saldo disponível da conta seja corretamente calculado como remaining_balance = current_balance - withdraw_amount.

Range Proof (BatchedRangeProofU64Data): Verifica que o saldo disponível restante após a retirada é não negativo e dentro de um intervalo especificado.
Para cada proof:
- Invoque o programa ZK ElGamal proof para verificar os dados do proof.
- Armazene os metadados específicos do proof em uma conta de "context state" do proof para uso em outras instruções.
Invoque a instrução ConfidentialTransferInstruction::Withdraw fornecendo as duas contas de proof.
Feche as contas de proof para recuperar o SOL utilizado para criá-las.

O diagrama a seguir mostra as etapas envolvidas na retirada de tokens do saldo disponível confidencial para o saldo público:

Withdraw Tokens

Instruções Necessárias

Para retirar tokens do saldo disponível confidencial para o saldo público, você deve:

Gerar um equality proof e um range proof no lado do cliente
Invocar o programa Zk ElGamal proof para verificar os proofs e inicializar as contas de "context state"
Invocar a instrução ConfidentialTransferInstruction::Withdraw fornecendo as duas contas de proof.
Fechar as duas contas de proof para recuperar o rent.

O exemplo em Rust abaixo gera os proofs com o crate spl-token-confidential-transfer-proof-generation, verifica cada um em uma conta de context state através do programa ZK ElGamal Proof, referencia ambas as contas na instrução de retirada e as fecha em seguida. O exemplo em TypeScript utiliza o helper getConfidentialWithdrawInstructionPlan de @solana-program/token-2022/confidential, que monta as mesmas contas de proof, a retirada e o fechamento como um plano de instrução multi-transação.

Código de Exemplo

O exemplo a seguir retira tokens do saldo confidencial disponível de volta ao saldo público. A conta já deve estar configurada para transferências confidenciais e ter um saldo confidencial disponível.

As transferências confidenciais dependem do programa ZK ElGamal Proof, que está habilitado na mainnet e devnet. Um solana-test-validator padrão não o habilita, mas um validator local com fork da mainnet, como o Surfpool, sim. Execute o exemplo em um desses (o código usa a devnet) com um pagador com fundos, e substitua os marcadores pelo seu mint e token account.

Rust



const ZK_PROOF_PROGRAM_ID: Pubkey =
    solana_pubkey::pubkey!("ZkE1Gama1Proof11111111111111111111111111111");

fn main() -> Result<()> {
    let rpc_client = RpcClient::new_with_commitment(
        String::from("https://api.devnet.solana.com"),
        CommitmentConfig::confirmed(),
    );

    // Owner = fee payer = token account owner. The account must already be
    // configured for confidential transfers with an available confidential
    // balance to withdraw from.
    let owner = load_keypair()?;
    let amount: u64 = 100;
    let decimals: u8 = 2;

    // Setup: create an available confidential balance to withdraw.
    let (mint, token_account) = setup_withdrawable_account(&rpc_client, &owner, amount, decimals)?;

    // Derive the owner's keys and read the current confidential available balance.
    let (elgamal_keypair, aes_key) = derive_confidential_keys(&owner, &token_account.to_bytes())
        .map_err(|e| anyhow::anyhow!("derive confidential keys: {e}"))?;

    let account_data = rpc_client.get_account(&token_account)?;
    let account = StateWithExtensions::<TokenAccount>::unpack(&account_data.data)?;
    let ct_extension = account.get_extension::<ConfidentialTransferAccount>()?;

    // The ElGamal available-balance ciphertext is required to build the proof.
    let available_balance: ElGamalCiphertext = ct_extension
        .available_balance
        .try_into()
        .map_err(|e| anyhow::anyhow!("decode available balance: {e:?}"))?;

    // Read the plaintext balance from the AES-encrypted decryptable balance.
    // ElGamal's decrypt_u32 only recovers values up to 2^32 raw units, so it
    // fails for realistic balances; the AES field has no such limit.
    let decryptable_balance: AeCiphertext = ct_extension
        .decryptable_available_balance
        .try_into()
        .map_err(|e| anyhow::anyhow!("decode decryptable balance: {e:?}"))?;
    let current_available = decryptable_balance
        .decrypt(&aes_key)
        .context("decrypt available balance")?;

    // Generate the equality and range proofs for the withdrawal.
    let proof_data = withdraw_proof_data(&available_balance, current_available, amount, &elgamal_keypair)
        .map_err(|e| anyhow::anyhow!("withdraw_proof_data: {e}"))?;

    let new_available = current_available
        .checked_sub(amount)
        .context("insufficient confidential balance")?;
    let new_decryptable: PodAeCiphertext = aes_key.encrypt(new_available).into();

    // The owner is the context-state authority for both proof accounts.
    let authority: Address = owner.pubkey().to_bytes().into();

    // Equality proof context state account.
    let equality_account = Keypair::new();
    let equality_size = size_of::<ProofContextState<CiphertextCommitmentEqualityProofContext>>();
    let equality_create_ix = system_instruction::create_account(
        &owner.pubkey(),
        &equality_account.pubkey(),
        rpc_client.get_minimum_balance_for_rent_exemption(equality_size)?,
        equality_size as u64,
        &ZK_PROOF_PROGRAM_ID,
    );
    let equality_verify_ix = ProofInstruction::VerifyCiphertextCommitmentEquality
        .encode_verify_proof(
            Some(ContextStateInfo {
                context_state_account: &Address::from(equality_account.pubkey().to_bytes()),
                context_state_authority: &authority,
            }),
            &proof_data.equality_proof_data,
        );
    send_tx(&rpc_client, &[equality_create_ix], &[&owner, &equality_account])?;
    send_tx(&rpc_client, &[equality_verify_ix], &[&owner])?;

    // Range proof context state account.
    let range_account = Keypair::new();
    let range_size = size_of::<ProofContextState<BatchedRangeProofContext>>();
    let range_create_ix = system_instruction::create_account(
        &owner.pubkey(),
        &range_account.pubkey(),
        rpc_client.get_minimum_balance_for_rent_exemption(range_size)?,
        range_size as u64,
        &ZK_PROOF_PROGRAM_ID,
    );
    let range_verify_ix = ProofInstruction::VerifyBatchedRangeProofU64.encode_verify_proof(
        Some(ContextStateInfo {
            context_state_account: &Address::from(range_account.pubkey().to_bytes()),
            context_state_authority: &authority,
        }),
        &proof_data.range_proof_data,
    );
    send_tx(&rpc_client, &[range_create_ix], &[&owner, &range_account])?;
    send_tx(&rpc_client, &[range_verify_ix], &[&owner])?;

    // Withdraw, referencing both pre-verified proof accounts.
    let withdraw_ixs = withdraw(
        &spl_token_2022::id(),
        &token_account,
        &mint,
        amount,
        decimals,
        &new_decryptable,
        &owner.pubkey(),
        &[&owner.pubkey()],
        ProofLocation::ContextStateAccount(&equality_account.pubkey()),
        ProofLocation::ContextStateAccount(&range_account.pubkey()),
    )?;
    let blockhash = rpc_client.get_latest_blockhash()?;
    let transaction =
        Transaction::new_signed_with_payer(&withdraw_ixs, Some(&owner.pubkey()), &[&owner], blockhash);
    let signature = rpc_client.send_and_confirm_transaction(&transaction)?;

    // Close both proof accounts to reclaim their rent.
    for account in [&equality_account, &range_account] {
        let close_ix = close_context_state(
            ContextStateInfo {
                context_state_account: &Address::from(account.pubkey().to_bytes()),
                context_state_authority: &authority,
            },
            &authority,
        );
        send_tx(&rpc_client, &[close_ix], &[&owner])?;
    }

    println!("Withdrew {amount} tokens to the public balance: {signature}");
    Ok(())
}

Typescript



const client = await createClient()
  .use(signerFromFile(join(homedir(), ".config/solana/id.json")))
  .use(
    solanaRpc({
      rpcUrl: "https://api.devnet.solana.com",
      maxConcurrency: 1
    })
  );

// The Solana CLI default keypair, used as fee payer, mint authority, and
// token account owner.
const owner = client.payer;
const depositAmount = 100n;
const amount = 25n;
const decimals = 2;

// Setup: create a confidential account with an available confidential balance.
const mint = await createConfidentialMint(client, owner, decimals);
const token = await createConfidentialTokenAccount(client, owner, mint);
await mintPublicTokens(client, owner, mint, token, depositAmount);
await depositTokens(client, owner, mint, token, depositAmount, decimals);
await applyPendingBalance(client, owner, mint, token);

// Derive the owner's recoverable ElGamal and AES keys, bound to (owner, mint).
const { elgamalKeypair, aesKey } = await deriveConfidentialKeys(owner, mint);

const tokenAccount = (await fetchToken(client.rpc, token)).data;

// Builds the equality + range proof accounts, the withdraw, and the closes as a
// multi-transaction instruction plan.
const plan = await getConfidentialWithdrawInstructionPlan({
  rpc: client.rpc,
  payer: owner,
  authority: owner,
  token,
  mint,
  tokenAccount,
  amount,
  decimals,
  elgamalKeypair,
  aesKey
});

const result = await client.sendTransactions(plan);
const summary = summarizeTransactionPlanResult(result);
const signature =
  summary.successfulTransactions[summary.successfulTransactions.length - 1]
    .context.signature;
console.log(`Withdrew ${amount} tokens to the public balance: ${signature}`);