rn-android-keystore

A React Native wrapper for Android Keystore that enables secure cryptographic key pair generation, storage, and payload signing on Android devices.

Features

• 🔐 Generate ECDSA key pairs stored in Android Keystore
• 📝 Sign payloads with private keys
• 🔑 Export public keys in PEM format
• 🛡️ Hardware-backed keystore support detection
• 🔄 Key management (create, delete, check existence)
• 📱 User authentication integration
• ⚙️ Secure key parameters configuration

Requirements

• React Native 0.60+
• Android API level 24+

Installation

npm install rn-android-keystore
# or
yarn add rn-android-keystore

Android Setup

No additional setup required. The package automatically links to your Android project.

Usage

Basic Example

import { RnAndroidKeystore } from 'rn-android-keystore';

// Generate a new key pair
const keyPair = await RnAndroidKeystore.generateKeyPair({
  alias: 'my-signing-key',
  algorithm: 'ECDSA',
  keySize: 256,
  hardwareBacked: true,
  userAuthenticationRequired: false,
});

console.log('Public Key PEM:', keyPair.publicKey);

API Reference

generateKeyPair(options)

Generates a new ECDSA key pair in the Android Keystore.

Parameters:

• alias (string, required): Unique identifier for the key pair
• algorithm (string, required): Cryptographic algorithm. Currently supports 'ECDSA'
• keySize (number, required): Key size in bits (e.g., 256)
• hardwareBacked (boolean, optional): Use hardware-backed keystore if available (default: true)
• userAuthenticationRequired (boolean, optional): Require user authentication to use the key (default: false)

Returns: Promise<KeyPairResult>

interface KeyPairResult {
  success: boolean;
  publicKey: string; // PEM formatted public key
  privateKey: string; // Key alias (private key is not exported)
  keySize: number;
  error?: string;
}

Example:

try {
  const result = await RnAndroidKeystore.generateKeyPair({
    alias: 'auth-key',
    algorithm: 'ECDSA',
    keySize: 256,
    hardwareBacked: true,
    userAuthenticationRequired: false,
  });

  if (result.success) {
    console.log('Key pair created:', result.publicKey);
  } else {
    console.error('Failed to create key pair:', result.error);
  }
} catch (error) {
  console.error('Error:', error);
}

getPublicKeyPEM(alias)

Retrieves the public key in PEM format for an existing key pair.

Parameters:

• alias (string, required): Key pair alias

Returns: Promise<PublicKeyResult>

interface PublicKeyResult {
  success: boolean;
  publicKeyPEM?: string;
  error?: string;
}

Example:

const result = await RnAndroidKeystore.getPublicKeyPEM('my-signing-key');
if (result.success) {
  console.log('Public Key:', result.publicKeyPEM);
}

sign(alias, payload, algorithm)

Signs a payload using the private key associated with the alias.

Parameters:

• alias (string, required): Key pair alias
• payload (string, required): Data to sign (will be encoded as UTF-8)
• algorithm (string, required): Signing algorithm (e.g., 'SHA256withECDSA')

Returns: Promise<SignResult>

interface SignResult {
  success: boolean;
  signature?: string; // Base64-encoded signature
  error?: string;
}

Example:

const payload = 'data to sign';
const result = await RnAndroidKeystore.sign(
  'my-signing-key',
  payload,
  'SHA256withECDSA'
);

if (result.success) {
  console.log('Signature:', result.signature);
}

deleteKey(alias)

Deletes a key pair from the Android Keystore.

Parameters:

• alias (string, required): Key pair alias

Returns: Promise<DeleteResult>

interface DeleteResult {
  success: boolean;
  error?: string;
}

Example:

const result = await RnAndroidKeystore.deleteKey('my-signing-key');
if (result.success) {
  console.log('Key deleted successfully');
}

keyExists(alias)

Checks if a key pair exists in the Android Keystore.

Parameters:

• alias (string, required): Key pair alias

Returns: Promise<KeyExistsResult>

interface KeyExistsResult {
  success: boolean;
  exists: boolean;
}

Example:

const result = await RnAndroidKeystore.keyExists('my-signing-key');
if (result.exists) {
  console.log('Key exists in Keystore');
} else {
  console.log('Key does not exist');
}

isHardwareBackedKeystoreAvailable()

Checks if the device has a hardware-backed keystore available.

Returns: Promise<HardwareCheckResult>

interface HardwareCheckResult {
  available: boolean;
}

Example:

const result = await RnAndroidKeystore.isHardwareBackedKeystoreAvailable();
if (result.available) {
  console.log('Hardware-backed keystore is available');
}

Complete Example: Authentication Token Signing

import { RnAndroidKeystore } from 'rn-android-keystore';

async function signAuthToken() {
  const keyAlias = 'auth-signing-key';
  
  // Check if key exists
  let keyExistsResult = await RnAndroidKeystore.keyExists(keyAlias);
  
  if (!keyExistsResult.exists) {
    // Create new key pair if it doesn't exist
    const createResult = await RnAndroidKeystore.generateKeyPair({
      alias: keyAlias,
      algorithm: 'ECDSA',
      keySize: 256,
      hardwareBacked: true,
      userAuthenticationRequired: false,
    });

    if (!createResult.success) {
      throw new Error(`Failed to create key: ${createResult.error}`);
    }

    console.log('Public Key:', createResult.publicKey);
  }

  // Sign a payload
  const payload = JSON.stringify({
    userId: '12345',
    timestamp: Date.now(),
  });

  const signResult = await RnAndroidKeystore.sign(
    keyAlias,
    payload,
    'SHA256withECDSA'
  );

  if (!signResult.success) {
    throw new Error(`Failed to sign: ${signResult.error}`);
  }

  return {
    payload,
    signature: signResult.signature,
  };
}

// Usage
signAuthToken()
  .then(result => {
    console.log('Signed token:', result);
  })
  .catch(error => {
    console.error('Error:', error);
  });

Error Handling

All functions return promises that resolve with a result object. Always check the success property before using the returned data:

const result = await RnAndroidKeystore.generateKeyPair({...});

if (!result.success) {
  console.error('Error:', result.error);
  return;
}

// Use result data

Platform Support

• Android: Full support (API 24+)

Security Considerations

1. Private Keys: Private keys are never exported and remain secure in Android Keystore
2. Hardware Backing: On devices with Strongbox, keys can be stored in hardware security modules
3. User Authentication: Enable userAuthenticationRequired to require biometric/PIN authentication before key usage
4. Key Aliases: Use meaningful, unique aliases for your keys
5. Payload Encoding: Payloads are automatically encoded as UTF-8

Contributing

• Development workflow
• Sending a pull request
• Code of conduct

License

MIT

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