Android: Store SecretKey in KeyStore

Android: Store SecretKey in KeyStore

Storing sensitive data like SecretKeys securely is crucial for Android app security. Android’s KeyStore provides a secure and robust way to store cryptographic keys. This article will guide you through the process of storing a SecretKey within Android KeyStore.

Understanding KeyStore

What is Android KeyStore?

Android KeyStore is a secure storage system built into the Android platform. It provides a hardware-backed secure environment for storing cryptographic keys, making them resistant to unauthorized access. KeyStore uses a combination of hardware security modules (HSMs) and software-based security measures to protect keys.

Benefits of Using KeyStore

• Security: KeyStore leverages hardware-backed security, making it difficult for attackers to extract keys.
• Accessibility: Keys are accessible only to the application that generated them, providing isolation.
• Compliance: KeyStore helps meet regulatory compliance requirements by ensuring secure key management.

Storing a SecretKey in KeyStore

Let’s break down the steps involved in storing a SecretKey in KeyStore:

1. Set Up KeyStore

// Obtain a KeyStore instance
KeyStore keyStore = KeyStore.getInstance("AndroidKeyStore");
// Initialize KeyStore
keyStore.load(null);

2. Generate a KeyPair

// Create a KeyGenerator with the desired algorithm (e.g., AES)
KeyGenerator keyGenerator = KeyGenerator.getInstance("AES", "AndroidKeyStore");
// Initialize KeyGenerator with specific parameters (e.g., key size)
keyGenerator.init(new KeyGenParameterSpec.Builder(
  "my_secret_key", // Key alias
  KeyProperties.PURPOSE_ENCRYPT | KeyProperties.PURPOSE_DECRYPT) // Key purpose
  .setBlockModes(KeyProperties.BLOCK_MODE_CBC) // Block mode
  .setEncryptionPaddings(KeyProperties.ENCRYPTION_PADDING_PKCS7) // Padding
  .build());
// Generate the key pair
SecretKey secretKey = keyGenerator.generateKey();

3. Store the SecretKey in KeyStore

// Get a KeyStore.Entry instance
KeyStore.Entry entry = new KeyStore.SecretKeyEntry(secretKey);
// Store the SecretKey in KeyStore
keyStore.setEntry("my_secret_key", entry, new KeyStore.ProtectionParameter(
  KeyProperties.PURPOSE_ENCRYPT | KeyProperties.PURPOSE_DECRYPT)); // Protection parameter

Retrieving the SecretKey

// Obtain the stored SecretKey
SecretKey storedSecretKey = (SecretKey) keyStore.getEntry("my_secret_key", new KeyStore.ProtectionParameter(
  KeyProperties.PURPOSE_ENCRYPT | KeyProperties.PURPOSE_DECRYPT)).getSecretKey();

Security Considerations

• Strong Encryption: Use strong encryption algorithms like AES with appropriate key sizes.
• Secure Key Generation: Always generate keys securely using KeyGenerator within KeyStore.
• Limited Access: Restrict access to the KeyStore to the necessary components of your application.
• Regular Updates: Keep your Android system and security patches up-to-date to protect against vulnerabilities.

Key Properties

KeyProperties offer fine-grained control over the security of your keys:

KeyProperties for Encryption/Decryption

KeyProperties for Block Modes

KeyProperties for Padding

Conclusion

Storing SecretKeys securely is paramount in Android development. Utilizing Android KeyStore provides a robust and secure solution. By following the steps outlined in this guide, you can ensure your sensitive data is properly protected.