Solana Integration

FHE-powered slot-based private token transfers on Solana.

Coming Soon

Solana support is coming soon. The programs and SDK are being finalized. Check back soon or follow our updates!

Overview

Private Token Slots lets you build confidential token vaults on Solana where:

Balances are encrypted (no one sees how much anyone holds)
Transfers happen privately (sender, receiver, amount all hidden)
Only the vault owner can decrypt balances

┌─────────────────────────────────────────────────────────┐
│                    Your Token Vault                      │
├─────────┬─────────┬─────────┬─────────┬────────────────┤
│  Slot 0 │  Slot 1 │  Slot 2 │  Slot 3 │  ... Slot 255  │
│  [ENC]  │  [ENC]  │  [ENC]  │  [ENC]  │     [ENC]      │
└─────────┴─────────┴─────────┴─────────┴────────────────┘
          ↓ Transfer 50 from Slot 0 → Slot 1
┌─────────┬─────────┬─────────┬─────────┬────────────────┐
│  [ENC]  │  [ENC]  │  [ENC]  │  [ENC]  │     [ENC]      │
└─────────┴─────────┴─────────┴─────────┴────────────────┘
    All balances remain encrypted throughout!

How It Works

Architecture

┌──────────────┐     ┌──────────────┐     ┌──────────────┐
│  Your Client │     │    Solana    │     │    ZKSDK     │
│              │     │              │     │  Coprocessor │
│ 1. Generate  │     │ 3. Vault CPI │     │              │
│    FHE keys  │────→│    to Oracle │────→│ 4. Compute   │
│              │     │              │     │    on FHE    │
│ 2. Encrypt   │     │              │     │              │
│    transfer  │     │              │     │ 5. Return    │
│              │     │              │◄────│    result    │
│ 6. Decrypt   │◄────│              │     │              │
│    (only you)│     │              │     │              │
└──────────────┘     └──────────────┘     └──────────────┘

What happens at each step:

Generate FHE keys — You create keys locally. Your secret key (clientKey) never leaves your machine.
Encrypt transfer — You encrypt the transfer details (which slot, how much). No one sees the plaintext.
Vault CPI — Your vault program sends the encrypted request to the coprocessor via Solana.
Compute on FHE — The coprocessor does math on encrypted data. It updates balances without knowing what they are.
Return result — New encrypted balances are written back to your vault on-chain.
Decrypt — Only you can decrypt and see the actual balances.

Why Deploy Your Own Vault Program?

You deploy your own vault program (Solana program) because:

Custom logic — Add your own deposit/withdrawal rules, access control, fees, etc.
Your keys — You generate FHE keys locally, register with coprocessor, link to your vault
Slots = accounts — Each slot (0-255) holds an encrypted balance within your vault

The coprocessor is a singleton — all vault programs CPI to the same coprocessor program. You don't deploy the coprocessor, just your vault.

How deposits work:

User calls your vault's deposit() → tokens go to vault's token account
Your vault CPIs to coprocessor → coprocessor encrypts amount into a slot
New balance blob is stored (currently in worker storage, future: IPFS/Arweave/user DB)
Vault on-chain gets updated CID pointer — only you (with clientKey) can decrypt

Zero-Trust Security

Your keys never leave your machine:

Component	Where It Lives	Who Can Access
ClientKey	Your machine only	Only you
ServerKey	ZKSDK Coprocessor	Can compute, cannot decrypt
PublicKey	ZKSDK Coprocessor	Anyone can encrypt to vault

The coprocessor mathematically cannot decrypt your data. It only has evaluation keys that can perform operations on ciphertext.

Quick Start

Install the SDK

npm install @zksdk/js-private-token-slots-fhe @coral-xyz/anchor @solana/web3.js @solana/spl-token

Network Configuration

// Program IDs (Solana Devnet)
const YOUR_VAULT_PROGRAM_ID = new PublicKey("YOUR_DEPLOYED_VAULT_PROGRAM_ID");
const COPROCESSOR_PROGRAM_ID = new PublicKey(
  "5LLZpQKc8DydeB6mnFU7SD6LRtNRBVRhzhUR3aNBbnmV"
);

// ZKSDK Alpha Network
const WORKER_URL = "https://alpha.coprocessor.zksdk.com";
const RPC_URL = "https://api.devnet.solana.com";

Legacy Naming

The on-chain program uses "oracle" naming (oracleProgram, oracleRequest). This is legacy terminology — conceptually it's a coprocessor that performs FHE computation.

Step-by-Step Guide

Understanding the Two IDs

Before starting, understand there are two separate IDs:

ID	What It Is	Where It Lives
Vault Key ID	64-char hex ID for your FHE keys	FHE Worker (coprocessor)
Vault Program ID	Your deployed Solana program	Solana blockchain

1. Generate FHE Keys & Register with Coprocessor

First, generate FHE keys locally and register them with the coprocessor. This gives you a vaultKeyId.

import { SlotVaultClient } from "@zksdk/js-private-token-slots-fhe";

const client = new SlotVaultClient({
  workerUrl: "https://alpha.coprocessor.zksdk.com",
});

// Generate FHE keys locally (ZERO TRUST!)
const { vaultKeyId, clientKey, serverKey, publicKey } =
  await client.createVault();

// ⚠️ CRITICAL: Save clientKey securely - only YOU can decrypt!
console.log("Vault Key ID:", vaultKeyId);
// Example: "a1b2c3d4e5f6...64 chars..."

What happens:

Keys generated on YOUR machine (clientKey never sent anywhere)
ServerKey + PublicKey sent to coprocessor
Coprocessor returns vaultKeyId (64-char hex)

2. Deploy Your Vault Program

Now deploy your Solana program. The reference vault has the ZKSDK already integrated.

Option A: Clone and deploy the reference vault

git clone https://github.com/zksdk-labs/example-solana-fhe-slot-vault
cd example-solana-fhe-slot-vault
anchor build
anchor deploy --provider.cluster devnet

After deploy, note your program ID:

solana address -k target/deploy/token_vault-keypair.json
# Example: "YourVau1tPr0gramID..."

Option B: Add SDK to your existing program

# Cargo.toml
[dependencies]
zksdk-private-token-slots = "0.1.0"

The SDK gives you the CPI functions to call the coprocessor.

3. Initialize Vault Account On-Chain

Now link your on-chain vault to your FHE keys using the vaultKeyId from Step 1.

// Derive vault PDA
const [vaultPda] = PublicKey.findProgramAddressSync(
  [Buffer.from("vault"), tokenMint.toBuffer()],
  YOUR_VAULT_PROGRAM_ID
);

// Initialize vault with your FHE vault key ID
await vaultProgram.methods
  .initializeVault(vaultKeyId)
  .accounts({
    vault: vaultPda,
    tokenMint: tokenMint,
    vaultTokenAccount: vaultTokenAccount,
    authority: wallet.publicKey,
    systemProgram: SystemProgram.programId,
  })
  .rpc();

4. Deposit Tokens

// Derive user position PDA
const [userPositionPda] = PublicKey.findProgramAddressSync(
  [Buffer.from("position"), vaultPda.toBuffer(), wallet.publicKey.toBuffer()],
  YOUR_VAULT_PROGRAM_ID
);

// Deposit 100 tokens (6 decimals)
await vaultProgram.methods
  .deposit(new anchor.BN(100_000_000))
  .accounts({
    vault: vaultPda,
    userPosition: userPositionPda,
    userTokenAccount: userTokenAccount,
    vaultTokenAccount: vaultTokenAccount,
    oracleProgram: COPROCESSOR_PROGRAM_ID, // Legacy name - this is the coprocessor
    user: wallet.publicKey,
    tokenProgram: TOKEN_PROGRAM_ID,
    systemProgram: SystemProgram.programId,
  })
  .rpc();

// Wait for coprocessor to create balance blob
let balanceBlobCid = "";
for (let i = 0; i < 30; i++) {
  await new Promise((r) => setTimeout(r, 2000));
  const vault = await vaultProgram.account.vault.fetch(vaultPda);
  if (vault.balanceBlobCid) {
    balanceBlobCid = vault.balanceBlobCid;
    break;
  }
}

5. Private Transfer

// Encrypt transfer: Slot 0 → Slot 1, Amount 50
const { encrypted_data } = client.encryptTransfer(0, 1, 50);

// Upload to coprocessor storage
const cid = await client.storeBalanceBlob(encrypted_data);

// Submit to Solana
const oracleRequestKeypair = Keypair.generate();
await vaultProgram.methods
  .requestPrivateTransfer(`c=${cid}`, 0, Buffer.from([]))
  .accounts({
    vault: vaultPda,
    userPosition: userPositionPda,
    oracleRequest: oracleRequestKeypair.publicKey,
    oracleProgram: COPROCESSOR_PROGRAM_ID, // Legacy name - this is the coprocessor
    user: wallet.publicKey,
    systemProgram: SystemProgram.programId,
  })
  .signers([oracleRequestKeypair])
  .rpc();

6. Wait & Decrypt

// Poll for completion
let resultCid = null;
for (let i = 0; i < 45; i++) {
  await new Promise((r) => setTimeout(r, 2000));
  const account = await oracleProgram.account.oracleRequest.fetch(
    oracleRequestKeypair.publicKey
  );
  const status = Object.keys(account.status)[0];

  if (status === "completed") {
    resultCid = account.resultCid;
    break;
  }
}

// Fetch and decrypt (only YOU can!)
const encryptedResult = await client.fetchBalanceBlob(resultCid);
const result = client.decryptResult(encryptedResult);

console.log("New balances:", result.balances); // [205, 50, 0, 0, ...]
console.log("Transfer valid:", result.isValid); // true

Rust Integration

For Solana programs that need to CPI to the coprocessor:

# Cargo.toml
[dependencies]
zksdk-private-token-slots = "0.1.0"

use zksdk_core::prelude::*;

pub fn request_transfer(ctx: Context<RequestTransfer>, input_cid: String) -> Result<()> {
    let metadata = VaultMetadataBuilder::new(
        &ctx.accounts.vault.key(),
        &ctx.accounts.vault.vault_key_id,
        &ctx.accounts.vault.balance_blob_cid,
    ).build();

    // Legacy function name - calls the coprocessor
    submit_oracle_request(
        &ctx.accounts.oracle_program,
        &ctx.accounts.oracle_request,
        &ctx.accounts.user,
        &ctx.accounts.system_program,
        CircuitType::CmuxTokenV1Linear.as_str(),
        vec![],
        &input_cid,
        &metadata,
    )?;

    Ok(())
}

Network Configuration

ZKSDK Alpha Network (Testnet)

Resource	Value
FHE Worker	`https://alpha.coprocessor.zksdk.com`
Coprocessor Program	`5LLZpQKc8DydeB6mnFU7SD6LRtNRBVRhzhUR3aNBbnmV`
Reference Vault	`BsVtbakPuEKJfsyFDXtCjWgHSxNbSXy1U4VPwsErSTDM` (example only)
Chain	Solana Devnet
RPC URL	`https://api.devnet.solana.com`

Deploy Your Own Vault

The Reference Vault above is just an example. You deploy your own vault program — the coprocessor listens to all vault programs that CPI to it.

Packages

Package	Platform	Version
@zksdk/core	npm	0.1.0
@zksdk/js-private-token-slots-fhe	npm	0.1.0
zksdk-core	crates.io	0.1.0
zksdk-private-token-slots	crates.io	0.1.0

API Reference

SlotVaultClient

import { SlotVaultClient } from '@zksdk/js-private-token-slots-fhe';

const client = new SlotVaultClient({
  workerUrl: string,
  apiKey?: string
});

// Create new vault (generates keys locally)
await client.createVault(): Promise<{
  vaultKeyId: string;   // 64-char hex ID
  clientKey: string;    // KEEP SECRET - for decryption
  serverKey: string;    // Safe to send - for computation
  publicKey: string;    // Safe to send - for encryption
}>;

// Load existing vault
await client.loadVault(vaultKeyId: string, clientKey?: string): Promise<VaultParams>;

// Encrypt transfer parameters
client.encryptTransfer(senderIdx: number, receiverIdx: number, amount: number): {
  encrypted_data: string;
  vault_key_id: string;
};

// Store encrypted blob
await client.storeBalanceBlob(encryptedBlob: string): Promise<string>;  // Returns CID

// Fetch encrypted blob
await client.fetchBalanceBlob(cid: string): Promise<string>;

// Decrypt result (requires ClientKey)
client.decryptResult(encryptedResultB64: string): {
  balances: number[];   // [205, 50, 0, 0, ...]
  isValid: boolean;     // Transfer validation result
};

Limitations (Alpha)

Current Limitations

Slot balances: 0-255 per slot (8-bit)
Slots per vault: Up to 256
Chain support: Solana devnet only
Not audited: Do not use with real value

Storage

Encrypted data is stored off-chain. Configure storage in your SDK setup:

const client = new SlotVaultClient({
  workerUrl: "https://alpha.coprocessor.zksdk.com",
  storageType: "postgres", // Current default
});

Type	Status
`postgres`	Available
`celestia`, `avail`, `eigenda`, `ipfs`	Coming Soon

See full Storage documentation for all options and configuration details.

Full End-to-End Example

A complete example using the published SDK.

Two Things You Need

Vault Key ID — 64-char hex from createVault() (Step 1)
- This registers your FHE keys with the coprocessor
- You pass this to initializeVault() on-chain
Your Vault Program — You deploy this on Solana (Step 2)
- Use the reference vault OR build your own with the SDK
- Your program CPIs to the singleton coprocessor

The coprocessor listens to ALL vault programs — you just deploy your vault, not the coprocessor.

import { SlotVaultClient } from "@zksdk/js-private-token-slots-fhe";
import { Connection, Keypair, PublicKey, SystemProgram } from "@solana/web3.js";
import * as anchor from "@coral-xyz/anchor";
import { TOKEN_PROGRAM_ID } from "@solana/spl-token";

/**
 * What talks to what:
 *
 * SDK (SlotVaultClient) ──HTTP──→ WORKER_URL (FHE coprocessor API)
 *   - createVault(), storeBalanceBlob(), fetchBalanceBlob()
 *   - encryptTransfer(), decryptResult() are local (no network)
 *
 * Your Vault Program ──CPI──→ COPROCESSOR_PROGRAM_ID (on-chain)
 *   - deposit(), requestPrivateTransfer()
 *   - The reference vault has this hardcoded already
 */

const WORKER_URL = "https://alpha.coprocessor.zksdk.com";
const RPC_URL = "https://api.devnet.solana.com";
const YOUR_VAULT_PROGRAM_ID = new PublicKey("YOUR_DEPLOYED_VAULT_PROGRAM_ID");
const COPROCESSOR_PROGRAM_ID = new PublicKey(
  "5LLZpQKc8DydeB6mnFU7SD6LRtNRBVRhzhUR3aNBbnmV"
);

async function main() {
  // ============ STEP 1: Generate FHE Keys & Register ============
  // Keys generated locally, only serverKey + publicKey sent to coprocessor
  const client = new SlotVaultClient({ workerUrl: WORKER_URL });
  const { vaultKeyId, clientKey } = await client.createVault();

  console.log("✅ Vault Key ID:", vaultKeyId);
  // ⚠️ SAVE clientKey SECURELY - only YOU can decrypt!

  // ============ STEP 2: Deploy Vault Program ============
  // Already done - YOUR_VAULT_PROGRAM_ID is your deployed program
  // See "Deploy Your Vault Program" section above

  // ============ STEP 3: Initialize Vault On-Chain ============
  // Links your on-chain vault to your FHE keys
  const [vaultPda] = PublicKey.findProgramAddressSync(
    [Buffer.from("vault"), tokenMint.toBuffer()],
    YOUR_VAULT_PROGRAM_ID
  );

  await vaultProgram.methods
    .initializeVault(vaultKeyId) // Pass the vault key ID from Step 1
    .accounts({
      vault: vaultPda,
      tokenMint: tokenMint,
      vaultTokenAccount: vaultTokenAccount,
      authority: wallet.publicKey,
      systemProgram: SystemProgram.programId,
    })
    .rpc();
  console.log("✅ Vault initialized on-chain");

  // ============ STEP 4: Deposit Tokens ============
  const [userPositionPda] = PublicKey.findProgramAddressSync(
    [Buffer.from("position"), vaultPda.toBuffer(), wallet.publicKey.toBuffer()],
    YOUR_VAULT_PROGRAM_ID
  );

  await vaultProgram.methods
    .deposit(new anchor.BN(100_000_000)) // 100 tokens (6 decimals)
    .accounts({
      vault: vaultPda,
      userPosition: userPositionPda,
      userTokenAccount: userTokenAccount,
      vaultTokenAccount: vaultTokenAccount,
      oracleProgram: COPROCESSOR_PROGRAM_ID,
      user: wallet.publicKey,
      tokenProgram: TOKEN_PROGRAM_ID,
      systemProgram: SystemProgram.programId,
    })
    .rpc();
  console.log("✅ Tokens deposited");

  // Wait for coprocessor to create balance blob
  let balanceBlobCid = "";
  for (let i = 0; i < 30; i++) {
    await new Promise((r) => setTimeout(r, 2000));
    const vault = await vaultProgram.account.vault.fetch(vaultPda);
    if (vault.balanceBlobCid) {
      balanceBlobCid = vault.balanceBlobCid;
      break;
    }
  }
  console.log("✅ Balance blob created:", balanceBlobCid);

  // ============ STEP 5: Encrypt & Submit Transfer ============
  const { encrypted_data } = client.encryptTransfer(0, 1, 50); // Slot 0 → Slot 1, 50 tokens
  const cid = await client.storeBalanceBlob(encrypted_data);
  console.log("✅ Encrypted transfer uploaded, CID:", cid);

  const oracleRequestKeypair = Keypair.generate();
  await vaultProgram.methods
    .requestPrivateTransfer(`c=${cid}`, 0, Buffer.from([]))
    .accounts({
      vault: vaultPda,
      userPosition: userPositionPda,
      oracleRequest: oracleRequestKeypair.publicKey,
      oracleProgram: COPROCESSOR_PROGRAM_ID,
      user: wallet.publicKey,
      systemProgram: SystemProgram.programId,
    })
    .signers([oracleRequestKeypair])
    .rpc();
  console.log("✅ Transfer request submitted");

  // ============ STEP 6: Wait & Decrypt ============
  let resultCid = null;
  for (let i = 0; i < 45; i++) {
    await new Promise((r) => setTimeout(r, 2000));
    const account = await oracleProgram.account.oracleRequest.fetch(
      oracleRequestKeypair.publicKey
    );
    if (Object.keys(account.status)[0] === "completed") {
      resultCid = account.resultCid;
      break;
    }
  }

  const encryptedResult = await client.fetchBalanceBlob(resultCid!);
  const result = client.decryptResult(encryptedResult);

  console.log("✅ New balances:", result.balances); // [205, 50, 0, 0, ...]
  console.log("✅ Transfer valid:", result.isValid);
}

main().catch(console.error);

The flow:

Generate keys locally → createVault() registers with coprocessor, returns vaultKeyId
Deploy vault program → Your Solana program (already done)
Initialize on-chain → Links vault PDA to your vaultKeyId
Deposit tokens → Coprocessor creates encrypted balance blob
Encrypt & submit → Encrypt transfer, upload, call vault
Decrypt result → Only you can decrypt with your clientKey

Run it:

npx ts-node your-e2e-test.ts

Support

GitHub: example-solana-fhe-slot-vault
Issues: Report bugs
Contact: Get in touch

Overview​

How It Works​

Architecture​

Why Deploy Your Own Vault Program?​

Zero-Trust Security​

Quick Start​

Install the SDK​

Network Configuration​

Step-by-Step Guide​

Understanding the Two IDs​

1. Generate FHE Keys & Register with Coprocessor​

2. Deploy Your Vault Program​

3. Initialize Vault Account On-Chain​

4. Deposit Tokens​

5. Private Transfer​

6. Wait & Decrypt​

Rust Integration​

Network Configuration​

ZKSDK Alpha Network (Testnet)​

Packages​

API Reference​

SlotVaultClient​

Limitations (Alpha)​

Storage​

Full End-to-End Example​

Support​

Overview

How It Works

Architecture

Why Deploy Your Own Vault Program?

Zero-Trust Security

Quick Start

Install the SDK

Network Configuration

Step-by-Step Guide

Understanding the Two IDs

1. Generate FHE Keys & Register with Coprocessor

2. Deploy Your Vault Program

3. Initialize Vault Account On-Chain

4. Deposit Tokens

5. Private Transfer

6. Wait & Decrypt

Rust Integration

Network Configuration

ZKSDK Alpha Network (Testnet)

Packages

API Reference

SlotVaultClient

Limitations (Alpha)

Storage

Full End-to-End Example

Support