PHP用Halite生成加密二维码，Android端解密工具及替代方案咨询

Hey there! Great call picking Halite for encryption—it's a rock-solid choice that sticks to modern cryptography best practices. Let's break down your options for decrypting those QR codes on Android:

Direct Libsodium Integration #

Halite is built on top of libsodium, so the most seamless approach is to use libsodium's official Android bindings. Here's how to get started:

• Add the dependency to your app's module-level build.gradle:

  implementation 'org.libsodium:libsodium-jni:2.0.1'
  

• Replicate Halite's decryption logic using libsodium's native functions. For example, if you used Halite's SymmetricCrypto class for encryption, you'll use crypto_secretbox_open_easy() on Android. Just make sure you're using the exact same key, nonce, and encryption parameters as your PHP code. Remember: Halite often auto-generates nonces, so you'll need to include the nonce in the QR data (it's not secret, just needs to be unique per encryption).

Alternative: Bouncy Castle Library #

If you prefer a pure Java/Kotlin solution without native dependencies, Bouncy Castle is a reliable alternative. However, you'll need to mirror Halite's default algorithms precisely:

• Halite uses XSalsa20-Poly1305 for symmetric encryption, so you'll need to implement this specific algorithm in Bouncy Castle.
• Double-check all parameters: nonce length (24 bytes for XSalsa20), key size (32 bytes), and authentication tag handling. A tiny mismatch here will cause decryption to fail entirely.

Critical Best Practices #

• Secure Key Management: Never hardcode your encryption key in the APK. Use Android's Keystore System to store the key securely on the device—this prevents the key from being extracted even if the app is compromised.
• QR Data Structure: When generating the QR code in PHP, package both the ciphertext and nonce (if applicable) into a single payload (like a JSON object). Your Android app can then parse this payload to extract the data needed for decryption.

内容的提问来源于stack exchange，提问作者Leonardo Linero