E2E Encryption with secp256k1

End-to-end encryption library using secp256k1 - compatible with EVM key pairs (Ethereum, Polygon, BSC). Perfect for Web3 apps that need private data.

Key Features

• Uses secp256k1 keys (EVM compatible format)
• Store encrypted data anywhere (IPFS, traditional DB, any chain)
• Uses EVM-style addresses and keys
• End-to-end encryption using ECDH + AES-256-GCM
• Works with any data type (objects, arrays, primitives)
• Data integrity verification built-in
• Supports notary pattern (dual access encryption)

Quick Start

const { Secp256k1E2E } = require('@zkthings/e2e-encryption-secp256k1');

// Initialize
const e2e = new Secp256k1E2E();

// Encrypt data for a recipient
const encrypted = await e2e.encryptFor(
    { secret: "sensitive data" },
    "0x742d35Cc6634C0532925a3b844Bc454e4438f44e", // EVM format address
    recipientPublicKey // secp256k1 public key
);

// Later: Recipient decrypts
const decrypted = await e2e.decrypt(encrypted, recipientPrivateKey);

API Reference

Node.js Usage (Secp256k1E2E)

const { Secp256k1E2E } = require('@zkthings/e2e-encryption-secp256k1');
const e2e = new Secp256k1E2E();

encryptFor(data, recipientAddress, recipientPublicKey)

Encrypts data for a specific Ethereum address.

• data: Any JSON-serializable data
• recipientAddress: Ethereum address (with or without '0x' prefix)
• recipientPublicKey: secp256k1 public key
• Returns: Promise<{ publicSignals: {...} }>

decrypt({ publicSignals, privateKey })

Decrypts data using a private key.

• publicSignals: Encrypted data object
• privateKey: secp256k1 private key (with '0x' prefix)
• Returns: Promise<any> - Original data

Browser Usage (Secp256k1E2EBrowser)

const { Secp256k1E2EBrowser } = require('@zkthings/e2e-encryption-secp256k1');
const e2e = new Secp256k1E2EBrowser();

Same API as Node.js version, but with browser-compatible implementations.

Advanced Features

Notary Access

Encrypt data with dual access (both user and notary can decrypt):

const encrypted = await e2e.encryptWithNotary(
    data,
    userAddress,
    userPublicKey,
    notaryAddress,
    notaryPublicKey
);

// User decryption
const userDecrypted = await e2e.decrypt({
    publicSignals: encrypted.publicSignals,
    privateKey: userPrivateKey,
    type: 'user'
});

// Notary decryption
const notaryDecrypted = await e2e.decrypt({
    publicSignals: encrypted.publicSignals,
    privateKey: notaryPrivateKey,
    type: 'notary'
});

Batch Decryption

Decrypt multiple encrypted items efficiently:

const decryptedItems = await e2e.decryptMyMany(
    encryptedItems,
    privateKey
);

Security

• Uses industry-standard ECDH for key exchange
• AES-256-GCM for symmetric encryption
• Includes authentication data to prevent tampering
• Ephemeral keys for perfect forward secrecy
• Secure key derivation using HKDF

Error Handling

The library throws descriptive errors for common issues:

try {
    await e2e.encryptFor(data, invalidAddress, publicKey);
} catch (error) {
    // Handles: Invalid address format, invalid keys, etc.
    console.error(error.message);
}

Browser Compatibility

The browser version (Secp256k1E2EBrowser) is specifically designed for browser environments:

• Uses crypto.subtle when available
• Falls back to polyfills when needed
• Handles browser-specific crypto API differences

Contributing

Please read CONTRIBUTING.md for details on our code of conduct and the process for submitting pull requests.

License

This project is licensed under the MIT License - see the LICENSE file for details.