Solana DocumentationTokens on SolanaExtensionsConfidential Transfer

Withdraw Tokens

How to withdraw tokens from confidential available balance

To withdraw tokens from confidential available balance to public balance:

  1. Create two proofs client side:

    Equality Proof (CiphertextCommitmentEqualityProofData): Verifies that the remaining available balance ciphertext after the withdrawal matches its corresponding Pedersen commitment, ensuring the account's new available balance is correctly computed as remaining_balance = current_balance - withdraw_amount.

    Range Proof (BatchedRangeProofU64Data): Verifies that the remaining available balance after withdrawal is non-negative and within a specified range.

  2. For each proof:

    • Invoke the ZK ElGamal proof program to verify the proof data.
    • Store the proof-specific metadata in a proof "context state" account to use in other instructions.

  3. Invoke the ConfidentialTransferInstruction::Withdraw instruction providing the two proof accounts.

  4. Close the proof accounts to recover the SOL used to create them.

The following diagram shows the steps involved in withdrawing tokens from confidential available balance to public balance:

Withdraw Tokens

Required Instructions

To withdraw tokens from confidential available balance to public balance, you must:

  • Generate an equality proof and range proof client-side
  • Invoke the Zk ElGamal proof program to verify the proofs and initialize the "context state" accounts
  • Invoke the ConfidentialTransferInstruction::Withdraw instruction providing the two proof accounts.
  • Close the two proof accounts to recover rent.

The spl_token_client crate provides the following methods:

  • confidential_transfer_create_context_state_account method that creates a proof account.
  • confidential_transfer_withdraw method that invokes the Withdraw instruction.
  • confidential_transfer_close_context_state_account method that closes a proof account.

Example Code

The following example demonstrates how to withdraw tokens from confidential available balance to public balance.

To run the example, start a local validator with the Token Extension Program cloned from mainnet using the following command. You must have the Solana CLI installed to start the local validator.

Terminal
$ 
solana-test-validator --clone-upgradeable-program TokenzQdBNbLqP5VEhdkAS6EPFLC1PHnBqCXEpPxuEb --url https://api.mainnet-beta.solana.com -r

At the time of writing, the Confidential Transfers isn't enabled on the default local validator. You must clone the mainnet Token Extension Program to run the example code.

use anyhow::{Context, Result};

use solana_client::nonblocking::rpc_client::RpcClient;

use solana_sdk::{

    commitment_config::CommitmentConfig,

    signature::{Keypair, Signer},

    transaction::Transaction,

};

use spl_associated_token_account::{

    get_associated_token_address_with_program_id, instruction::create_associated_token_account,

};

use spl_token_client::{

    client::{ProgramRpcClient, ProgramRpcClientSendTransaction},

    spl_token_2022::{

        extension::{

            confidential_transfer::{

                account_info::WithdrawAccountInfo,

                ConfidentialTransferAccount,

                instruction::{configure_account, PubkeyValidityProofData},

            },

            BaseStateWithExtensions, ExtensionType,

        },

        id as token_2022_program_id,

        instruction::reallocate,

        solana_zk_sdk::encryption::{auth_encryption::*, elgamal::*},

    },

    token::{ExtensionInitializationParams, Token},

};

use spl_token_confidential_transfer_proof_extraction::instruction::{ProofData, ProofLocation};

use spl_token_confidential_transfer_proof_generation::withdraw::WithdrawProofData;

use std::sync::Arc;



#[tokio::main]

async fn main() -> Result<()> {

    // Create connection to local test validator

    let rpc_client = Arc::new(RpcClient::new_with_commitment(

        String::from("http://localhost:8899"),

        CommitmentConfig::confirmed(),

    ));



    // Load the default Solana CLI keypair to use as the fee payer

    // This will be the wallet paying for the transaction fees

    // Use Arc to prevent multiple clones of the keypair

    let payer = Arc::new(load_keypair()?);

    println!("Using payer: {}", payer.pubkey());



    // Generate a new keypair to use as the address of the token mint

    let mint = Keypair::new();

    println!("Mint keypair generated: {}", mint.pubkey());



    // Set up program client for Token client

    let program_client = ProgramRpcClient::new(rpc_client.clone(), ProgramRpcClientSendTransaction);



    // Number of decimals for the mint

    let decimals = 9;



    // Create a token client for the Token-2022 program

    // This provides high-level methods for token operations

    let token = Token::new(

        Arc::new(program_client),

        &token_2022_program_id(), // Use the Token-2022 program (newer version with extensions)

        &mint.pubkey(),           // Address of the new token mint

        Some(decimals),           // Number of decimal places

        payer.clone(),            // Fee payer for transactions

    );



    // Create extension initialization parameters for the mint

    // The ConfidentialTransferMint extension enables confidential (private) transfers of tokens

    let extension_initialization_params =

        vec![ExtensionInitializationParams::ConfidentialTransferMint {

            authority: Some(payer.pubkey()), // Authority that can modify confidential transfer settings

            auto_approve_new_accounts: true, // Automatically approve new confidential accounts

            auditor_elgamal_pubkey: None,    // Optional auditor ElGamal public key

        }];



    // Create and initialize the mint with the ConfidentialTransferMint extension

    // This sends a transaction to create the new token mint

    let transaction_signature = token

        .create_mint(

            &payer.pubkey(),                 // Mint authority - can mint new tokens

            Some(&payer.pubkey()),           // Freeze authority - can freeze token accounts

            extension_initialization_params, // Add the ConfidentialTransferMint extension

            &[&mint],                        // Mint keypair needed as signer

        )

        .await?;



    // Print results for user verification

    println!("Mint Address: {}", mint.pubkey());

    println!(

        "Mint Creation Transaction Signature: {}",

        transaction_signature

    );



    // ===== Create and configure token account for confidential transfers =====

    println!("\nCreate and configure token account for confidential transfers");



    // Get the associated token account address for the owner

    let token_account_pubkey = get_associated_token_address_with_program_id(

        &payer.pubkey(),          // Token account owner

        &mint.pubkey(),           // Mint

        &token_2022_program_id(), // Token program ID

    );

    println!("Token Account Address: {}", token_account_pubkey);



    // Step 1: Create the associated token account

    let create_associated_token_account_instruction = create_associated_token_account(

        &payer.pubkey(),          // Funding account

        &payer.pubkey(),          // Token account owner

        &mint.pubkey(),           // Mint

        &token_2022_program_id(), // Token program ID

    );



    // Step 2: Reallocate the token account to include space for the ConfidentialTransferAccount extension

    let reallocate_instruction = reallocate(

        &token_2022_program_id(),                      // Token program ID

        &token_account_pubkey,                         // Token account

        &payer.pubkey(),                               // Payer

        &payer.pubkey(),                               // Token account owner

        &[&payer.pubkey()],                            // Signers

        &[ExtensionType::ConfidentialTransferAccount], // Extension to reallocate space for

    )?;



    // Step 3: Generate the ElGamal keypair and AES key for token account

    let elgamal_keypair = ElGamalKeypair::new_from_signer(&payer, &token_account_pubkey.to_bytes())

        .expect("Failed to create ElGamal keypair");

    let aes_key = AeKey::new_from_signer(&payer, &token_account_pubkey.to_bytes())

        .expect("Failed to create AES key");



    // The maximum number of Deposit and Transfer instructions that can

    // credit pending_balance before the ApplyPendingBalance instruction must be executed

    let maximum_pending_balance_credit_counter = 65536;



    // Initial token balance is 0

    let decryptable_balance = aes_key.encrypt(0);



    // Generate the proof data client-side

    let proof_data = PubkeyValidityProofData::new(&elgamal_keypair)

        .map_err(|_| anyhow::anyhow!("Failed to generate proof data"))?;



    // Indicate that proof is included in the same transaction

    let proof_location =

        ProofLocation::InstructionOffset(1.try_into()?, ProofData::InstructionData(&proof_data));



    // Step 4: Create instructions to configure the account for confidential transfers

    let configure_account_instructions = configure_account(

        &token_2022_program_id(),               // Program ID

        &token_account_pubkey,                  // Token account

        &mint.pubkey(),                         // Mint

        &decryptable_balance.into(),            // Initial balance

        maximum_pending_balance_credit_counter, // Maximum pending balance credit counter

        &payer.pubkey(),                        // Token Account Owner

        &[],                                    // Additional signers

        proof_location,                         // Proof location

    )?;



    // Combine all instructions

    let mut instructions = vec![

        create_associated_token_account_instruction,

        reallocate_instruction,

    ];

    instructions.extend(configure_account_instructions);



    // Create and send the transaction

    let recent_blockhash = rpc_client.get_latest_blockhash().await?;

    let transaction = Transaction::new_signed_with_payer(

        &instructions,

        Some(&payer.pubkey()),

        &[&*payer],

        recent_blockhash,

    );



    let setup_signature = rpc_client

        .send_and_confirm_transaction(&transaction)

        .await?;

    println!(

        "Token Account Setup Transaction Signature: {}",

        setup_signature

    );



    // Mint some tokens to the newly created token account

    // This gives the account some tokens to work with

    let mint_signature = token

        .mint_to(

            &token_account_pubkey,            // Destination account

            &payer.pubkey(),                  // Mint authority

            100 * 10u64.pow(decimals as u32), // Amount (100 tokens with decimal precision)

            &[&payer],                        // Signers

        )

        .await?;



    println!("Token Minting Transaction Signature: {}", mint_signature);



    // Deposit the tokens to confidential state

    // This converts regular tokens to confidential tokens

    println!("Deposit tokens to confidential state pending balance");

    let deposit_signature = token

        .confidential_transfer_deposit(

            &token_account_pubkey,            // The token account

            &payer.pubkey(),                  // Authority (owner) of the account

            100 * 10u64.pow(decimals as u32), // Amount to deposit (100 tokens)

            decimals,                         // Decimals of the token

            &[&payer],                        // Signers (owner must sign)

        )

        .await?;



    println!(

        "Confidential Transfer Deposit Signature: {}",

        deposit_signature

    );



    // Apply the pending balance to make funds available

    println!("Apply pending balance to available balance");

    let apply_signature = token

        .confidential_transfer_apply_pending_balance(

            &token_account_pubkey,    // The token account

            &payer.pubkey(),          // Authority (owner) of the account

            None,                     // Optional new decryptable available balance

            elgamal_keypair.secret(), // ElGamal secret key encryption

            &aes_key,                 // AES key for encryption

            &[&payer],                // Signers (owner must sign)

        )

        .await?;



    println!("Apply Pending Balance Signature: {}", apply_signature);



    // ===== Withdraw half of the tokens from confidential state =====

    println!("\nWithdraw tokens from confidential available balance");



    // Calculate the withdraw amount (half of the deposited amount)

    let withdraw_amount = 50 * 10u64.pow(decimals as u32); // Half of the 100 tokens deposited



    // Get the token account data to access the confidential transfer extension

    let token_account = token.get_account_info(&token_account_pubkey).await?;



    // Unpack the ConfidentialTransferAccount extension portion of the token account data

    let extension_data = token_account.get_extension::<ConfidentialTransferAccount>()?;



    // Confidential Transfer extension information needed to construct a `Withdraw` instruction

    let withdraw_account_info =

        WithdrawAccountInfo::new(

            extension_data,

        );



    // Create keypairs for the proof accounts

    let equality_proof_context_state_keypair = Keypair::new();

    let equality_proof_context_state_pubkey = equality_proof_context_state_keypair.pubkey();

    let range_proof_context_state_keypair = Keypair::new();

    let range_proof_context_state_pubkey = range_proof_context_state_keypair.pubkey();



    // Create a withdraw proof data

    let WithdrawProofData {

        equality_proof_data,

        range_proof_data,

    } = withdraw_account_info.generate_proof_data(

        withdraw_amount,  // Amount to withdraw from confidential state

        &elgamal_keypair, // ElGamal keypair for encryption

        &aes_key,         // AES key for encryption

    )?;



    // Generate the equality proof account

    println!("Create equality proof context state account");

    let equality_proof_signature = token

        .confidential_transfer_create_context_state_account(

            &equality_proof_context_state_pubkey, // Public key of the new equality proof context state account

            &payer.pubkey(), // Authority that can close the context state account

            &equality_proof_data, // Proof data for the equality proof verification

            false, // False: combine account creation and proof verification in one transaction

            &[&equality_proof_context_state_keypair], // Signer for the new account

        )

        .await?;

    println!(

        "Equality Proof Context State Account Signature: {}",

        equality_proof_signature

    );



    // Generate the range proof account

    println!("Create range proof context state account");

    let range_proof_signature = token

        .confidential_transfer_create_context_state_account(

            &range_proof_context_state_pubkey, // Public key of the new range proof context state account

            &payer.pubkey(),                   // Authority that can close the context state account

            &range_proof_data,                 // Proof data for the range proof verification

            true, // True: split account creation and proof verification into separate transactions (for large proofs)

            &[&range_proof_context_state_keypair], // Signer for the new account

        )

        .await?;

    println!(

        "Range Proof Context State Account Signature: {}",

        range_proof_signature

    );



    // Perform the withdrawal

    println!("Execute withdrawal transaction");

    let withdraw_signature = token

        .confidential_transfer_withdraw(

            &token_account_pubkey, // Token account to withdraw from

            &payer.pubkey(),       // Owner of the token account

            Some(&spl_token_client::token::ProofAccount::ContextAccount(

                equality_proof_context_state_pubkey, // Reference to the equality proof account

            )),

            Some(&spl_token_client::token::ProofAccount::ContextAccount(

                range_proof_context_state_pubkey, // Reference to the range proof account

            )),

            withdraw_amount,             // Amount to withdraw from confidential state

            decimals,                    // Decimal precision of the token

            Some(withdraw_account_info), // Data from confidential transfer extension for proof verification

            &elgamal_keypair, // ElGamal keypair for encryption

            &aes_key,         // AES key for encryption

            &[&payer],        // Owner must sign the transaction

        )

        .await?;

    println!("Withdraw Transaction Signature: {}", withdraw_signature);



    // Close the context state accounts to recover rent

    println!("Close equality proof context state account");

    let close_equality_signature = token

        .confidential_transfer_close_context_state_account(

            &equality_proof_context_state_pubkey, // Equality proof context state account to close

            &token_account_pubkey,                // Account that will receive the lamports

            &payer.pubkey(),                      // Authority allowed to close the account

            &[&payer],                            // Authority must sign

        )

        .await?;

    println!(

        "Close Equality Proof Account Signature: {}",

        close_equality_signature

    );



    println!("Close range proof context state account");

    let close_range_signature = token

        .confidential_transfer_close_context_state_account(

            &range_proof_context_state_pubkey, // Range proof context state account to close

            &token_account_pubkey,             // Account that will receive the lamports

            &payer.pubkey(),                   // Authority allowed to close the account

            &[&payer],                         // Authority must sign

        )

        .await?;

    println!(

        "Close Range Proof Account Signature: {}",

        close_range_signature

    );

    Ok(())

}



// Load the keypair from the default Solana CLI keypair path (~/.config/solana/id.json)

// This enables using the same wallet as the Solana CLI tools

fn load_keypair() -> Result<Keypair> {

    // Get the default keypair path

    let keypair_path = dirs::home_dir()

        .context("Could not find home directory")?

        .join(".config/solana/id.json");



    // Read the keypair file directly into bytes using serde_json

    // The keypair file is a JSON array of bytes

    let file = std::fs::File::open(&keypair_path)?;

    let keypair_bytes: Vec<u8> = serde_json::from_reader(file)?;



    // Create keypair from the loaded bytes

    // This converts the byte array into a keypair

    let keypair = Keypair::from_bytes(&keypair_bytes)?;



    Ok(keypair)

}

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